Mountains Discovered On Titan, Saturn's Largest Moon

Source:

http://www.sciencedaily.com/releases/2007/12/071220223729.htm

ScienceDaily (Dec. 21, 2007) — By analyzing images from NASA’s Cassini Radar instrument, a Brigham Young University professor helped discover and analyze mountains on Saturn’s largest moon, additional evidence that it has some of the most earthlike processes of any celestial body in the solar system.

According to the study, Titan’s mountains are most likely made of water ice and are relatively small in height, at most 2 km (1.25 mi) from base to peak. The consistently short height of Titan’s mountains provides evidence that they have been subject to similar amounts of erosion, that they are roughly the same age or that the materials are behaving in a way that prevents them from growing taller.
Planetary scientist Jani Radebaugh is lead author of the discovery paper in the December issue of the astronomy journal Icarus. The images retrieved by the Cassini Radar are the first images showing the details of Titan’s surface – previous spacecraft and telescopes could not pierce the haze and clouds surrounding the moon to the surface.
The discovery of mountains on Titan grew out of Radebaugh’s collaboration with a research team that recently found sand dunes and methane lakes on Titan. Radebaugh was a coauthor on the Science study that introduced Titan’s sand dunes in May 2006 as well as the Nature study that introduced Titan’s methane lakes in January 2007.
“Since this is the first time humans have been able to see through the haze to Titan’s surface, it was shocking to find these mountains, channels, dunes, and cryo-lava flows,” Radebaugh said. “We had to wait until we got all the way to Titan to see these landforms that are so similar to Earth.”
Upon receiving the images from NASA, Radebaugh, in collaboration with the Cassini Radar Team, discovered the mountains and began analyzing their characteristics. With no instrument to precisely measure the mountains’ height, Radebaugh looked at the light and shadows in the radar images to calculate the mountains’ slope and then derive their height.
“Dr. Radebaugh’s work represents an important advance in our understanding of that icy moon and the Earth,” said Dr. Jason Barnes, a research scientist at the NASA Ames Research Center. “Her discovery tells us about the mountain-building process in general and about Titan’s crust in particular.”
Prior to Cassini, scientists assumed that most of the topography on Titan would be impact structures, yet these new findings reveal that similar to Earth, the mountains were formed through geological processes on the moon.
Radebaugh proposes four possible explanations for the formation of the mountains on Titan. The first possibility is that the mountains were thrust up from crustal compression, horizontal forces smashing the crust together and upward. Alternatively, Titan’s mountains may have formed through spreading or separation of the crust, in the same way that Utah’s Wasatch Mountains separated from the Oquirrh Mountains to the west.
It’s also possible some of the mountains have been created by impact craters that threw out blocks of material, or that erosion stripped away a preexisting layer of material and left high-standing features like the mountains.
Since the processes on Titan are so similar to Earth’s, Radebaugh also concluded in the study that Titan may be an interesting laboratory for studying Earth. Like Earth, Titan possesses the primary ingredients for life, namely energy, water and organics. Information from Titan will help scientists better understand the Earth’s origin, formative processes and development of life.
“We still don’t understand exactly how life began on Earth, so if we can understand how the fundamentals of these processes may be starting in some laboratory like Titan, it will help us understand the Earth a lot better,” Radebaugh said.
In addition to analyzing images from space, Radebaugh also looks on planet earth for clues about the geology of other planets, moons and objects in the solar system. Two years ago Radebaugh scoured Antarctica for meteorites with the Antarctic Search for Meteorites (ANSMET) program. Through field work at Hawaiian volcanoes, she has also worked with students to utilize a technique for using a camcorder to measure eruption temperatures in the hope of learning more about volcanoes on Io, a moon of Jupiter.
Adapted from materials provided by Brigham Young University.

Fausto Intilla

www.oloscience.com

10,000 Earths' Worth Of Fresh Dust Found Near Star Explosion

Source:

http://www.sciencedaily.com/releases/2007/12/071220132156.htm

ScienceDaily (Dec. 21, 2007) — Astronomers have at last found definitive evidence that the universe's first dust – the celestial stuff that seeded future generations of stars and planets – was forged in the explosions of massive stars.

The findings, made with NASA's Spitzer Space Telescope, are the most significant clue yet in the longstanding mystery of where the dust in our very young universe came from. Scientists had suspected that exploding stars, or supernovae, were the primary source, but nobody had been able to demonstrate that they can create copious amounts of dust – until now. Spitzer's sensitive infrared detectors have found 10,000 Earth masses worth of dust in the blown-out remains of the well-known supernova remnant Cassiopeia A.
"Now we can say unambiguously that dust – and lots of it – was formed in the ejecta of the Cassiopeia A explosion. This finding was possible because Cassiopeia A is in our own galaxy, where it is close enough to study in detail," said Jeonghee Rho of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena. Rho is the lead author of a new report about the discovery appearing in the Jan. 20 issue of the Astrophysical Journal.
Space dust is everywhere in the cosmos, in our own neck of the universe and all the way back billions of light-years away in our infant universe. Developing stars need dust to cool down enough to collapse and ignite, while planets and living creatures consist of the powdery substance. In our nearby universe, dust is pumped out by dying stars like our sun. But back when the universe was young, sun-like stars hadn't been around long enough to die and leave dust.
That's where supernovae come in. These violent explosions occur when the most massive stars in the universe die. Because massive stars don't live very long, theorists reasoned that the very first exploding massive stars could be the suppliers of the unaccounted-for dust. These first stars, called Population III, are the only stars that formed without any dust.
Other objects in addition to supernovae might also contribute to the universe's first dust. Spitzer recently found evidence that highly energetic black holes, called quasars, could, together with supernovae, manufacture some dust in their winds.
Rho and her colleagues analyzed the Cassopeia A supernova remnant, located about 11,000 light-years away. Though this remnant is not from the early universe, its proximity to us makes it easier to address the question of whether supernovae have the ability to synthesize significant amounts of dust. The astronomers analyzed the infrared light coming from Cassiopeia A using Spitzer's infrared spectrograph, which spreads light apart to reveal the signatures of different elements and molecules. "Because Spitzer is extremely sensitive to dust, we were able to make high-resolution maps of dust in the entire structure," said Rho.
The map reveals the quantity, location and composition of the supernova remnant's dust, which includes proto-silicates, silicon dioxide, iron oxide, pyroxene, carbon, aluminium oxide and other compounds. One of the first things the astronomers noticed was that the dust matches up perfectly with the gas, or ejecta, known to have been expelled in the explosion. This is the smoking gun indicating the dust was freshly made in the ejecta from the stellar blast. "Dust forms a few to several hundred days after these energetic explosions, when the temperature of gas in the ejecta cools down," said Takashi Kozasa, a co-author at the Hokkaido University in Japan.
The team was surprised to find freshly-made dust deeper inside the remnant as well. This cooler dust, mixed in with gas referred to as the unshocked ejecta, had never been seen before.
All the dust around the remnant, both warm and cold, adds up to about three percent of the mass of the sun, or 10,000 Earths. This is just enough to explain where a large fraction, but not all, of the universe's early dust came from. "Perhaps at least some of the unexplained portion is much colder dust, which could be observed with upcoming telescopes, such as Herschel," said Haley Gomez, a co-author at University of Wales, Cardiff. The Herschel Space Observatory, scheduled to launch in 2008, is a European Space Agency mission with significant NASA participation.
Rho also said that more studies of other supernovae from near to far are needed to put this issue to rest. She notes that the rate at which dust is destroyed – a factor in determining how much dust is needed to explain the dusty early universe – is still poorly understood.
The principal investigator of the research program, and a co-author of the paper, is Lawrence Rudnick of the University of Minnesota, Twin Cities. Other co-authors include W.T. Reach of the Spitzer Science Center; J. D. Smith of the Steward Observatory, Tucson, Ariz.; T. Delaney of the Massachusetts Institute of Technology, Cambridge; J.A. Ennis of the University of Minnesota; and A. Tappe of the Spitzer Science Center and the Harvard Smithsonian Center for Astrophysics, Cambridge, Mass.
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Fausto Intilla

www.oloscience.com

Astronomers Monitor Asteroid To Pass Near Mars

Source:

http://www.sciencedaily.com/releases/2007/12/071221162707.htm

ScienceDaily (Dec. 21, 2007) — Astronomers funded by NASA are monitoring the trajectory of an asteroid estimated to be 50 meters (164 feet) wide that is expected to cross Mars' orbital path early next year. Observations provided by the astronomers and analyzed by NASA's Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif., indicate the object may pass within 30,000 miles of Mars at about 6 a.m. EST (3 a.m. PST) on Jan. 30, 2008.

"Right now asteroid 2007 WD5 is about half-way between Earth and Mars and closing the distance at a speed of about 27,900 miles per hour," said Don Yeomans, manager of the Near Earth Object Office at JPL. "Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid's trajectory."
NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," plots the orbits of these objects to determine if any could be potentially hazardous to our planet.
Asteroid 2007 WD5 was first discovered on Nov. 20, 2007, by the NASA-funded Catalina Sky Survey and put on a "watch list" because its orbit passes near Earth. Further observations from both the NASA-funded Spacewatch at Kitt Peak, Ariz., and the Magdalena Ridge Observatory in New Mexico gave scientists enough data to determine that the asteroid was not a danger to Earth, but could potentially impact Mars. This makes it a member of an interesting class of small objects that are both near Earth objects and "Mars crossers."
Because of current uncertainties about the asteroid's exact orbit, there is a 1-in-75 chance of 2007 WD5 impacting Mars. If this unlikely event were to occur, it would be somewhere within a broad swath across the planet north of where the Opportunity rover is located.
"We estimate such impacts occur on Mars every thousand years or so," said Steve Chesley, a scientist at JPL. "If 2007 WD5 were to thump Mars on Jan. 30, we calculate it would hit at about 30,000 miles per hour and might create a crater more than half-a-mile wide." The Mars Rover Opportunity is exploring a crater approximately this size right now.
Such a collision could release about three megatons of energy. Scientists believe an event of comparable magnitude occurred here on Earth in 1908 in Tunguska, Siberia, but no crater was created. The object was disintegrated by Earth's thicker atmosphere before it hit the ground, although the air blast devastated a large area of unpopulated forest.
NASA and its partners will continue to track asteroid 2007 WD5 and will provide an update in January when further information is available. For more information on the Near Earth Object program, visit: http://neo.jpl.nasa.gov/.
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Fausto Intilla

www.oloscience.com

Mars Rovers Find New Evidence Of 'Habitable Niche'

Source:

http://www.sciencedaily.com/releases/2007/12/071221161922.htm

ScienceDaily (Dec. 22, 2007) — Inch by power-conserving inch, drivers on Earth have moved the Mars rover Spirit to a spot where it has its best chance at surviving a third Martian winter -- and where it will celebrate its fourth anniversary (in Earth years) since bouncing down on Mars for a projected 90-day mission in January 2004.

Meanwhile, researchers are considering the implications of what Cornell's Steve Squyres, principal investigator for NASA's Mars Exploration Rover mission, calls "one of the most significant" mission discoveries to date: silica-rich deposits uncovered in May by Spirit's lame front wheel that provide new evidence for a once-habitable environment in Gusev Crater.
Squyres and colleagues reported the silica deposits at the annual meeting of the American Geophysical Union in early December in San Francisco.
On the other side of Mars, Spirit's still-healthy twin Opportunity is creeping slowly down the inside of Victoria Crater, where layers of exposed rock are confirming findings made at the much smaller Eagle and Endurance craters -- and where deeper layers could offer new insight into the planet's history.
Spirit, which has been driving backward since its right front wheel stopped turning in March 2006, was exploring near a plateau in the Gusev Crater known as Home Plate when scientists noticed that upturned soil in the wake of its dragging wheel appeared unusually bright.
Measurements by the rover's alpha particle X-ray spectrometer and mini-thermal emission spectrometer showed the soil to be about 90 percent amorphous silica -- a substance associated with life-supporting environments on Earth.
"This is one of the most powerful pieces of evidence for formerly habitable conditions that we have found," said Squyres, Cornell's Goldwin Smith Professor of Planetary Science, in a Dec. 11 interview with the BBC.
On Earth, silica deposits are found at hot springs, where hot water dissolves silica in rock below the surface, then rises and cools, causing the silica to precipitate out near the surface; and at fumaroles, where hot acidic water or vapors seep through rock, dissolving away other elements but leaving silica behind.
"Either place on Earth is teeming with microbial life," said Squyres. "So this is, either way, a representation of what in the past was a local habitable environment -- a little habitable niche on the surface of Mars."
The discovery was reminiscent of Spirit's journey to winter safety last year, when it uncovered (and briefly got mired in) patches of bright soil that contained high levels of sulfur -- another possible indicator of past hydrothermal activity.
Unlike last year, though, Spirit enters this Martian winter handicapped by dusty solar panels -- the result of giant dust storms in June and July. So the rover's power levels, which currently range between approximately 290 and 250 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour; full power for the rovers is 800-900 watt-hours) -- could drop to dangerous levels in the dwindling winter sunlight.
Spirit's perch is currently at a 15-degree tilt on the north-facing slope of the Home Plate plateau, said Jim Bell, Cornell associate professor of astronomy and leader of the mission's Pancam color camera team. As the sun moves lower in the Martian sky, drivers will nudge the rover to a steeper angle.
"The fact that we've gotten to a good tilt, and we're going to get to a better tilt, is a good sign," said Bell. Still, he added, any work the rover does over the winter -- collecting Pancam images of its surroundings, for example -- will be strictly low-exertion.
"Most of 2008 is going to be a quiet time for Spirit," he said. "It's really about survival."
Adapted from materials provided by Cornell University.

Fausto Intilla

www.oloscience.com

'Solar Flare' Detected From Star 150 Light Years Away

Source:

http://www.sciencedaily.com/releases/2007/12/071219103049.htm

ScienceDaily (Dec. 19, 2007) — Using observations from ESO's VLT, astronomers were able for the first time to reconstruct the site of a flare on a solar-like star located 150 light years away. The study of this young star, nicknamed 'Speedy Mic' because of its fast rotation, will help scientists better understand the youth of our Sun.

The astronomers [1] observed the star BO Microscopii [2] during two consecutive nights in October 2006, simultaneously with the UVES spectrograph on ESO's Very Large Telescope and ESA's XMM-Newton X-ray satellite.
Using a technique called 'Doppler imaging' [3], the astronomers reconstructed images of the surface of the star, detecting the presence of several spots. A few are near the visible pole, while most spots are asymmetrically distributed at mid-latitudes.
"The image we could secure of Speedy Mic is, given its distance, a real achievement, that allows us to localise for the first time ever the source of a flare and its surrounding," says Uwe Wolter, lead author of the paper relating the discovery.
The X-ray observations indeed identified several flares, which are sudden and vast releases of energy. For one of them, the astronomers could pinpoint its origin on the surface of the star. The flare, lasting about 4 hours, was a hundred times more energetic than a large solar flare and considerably larger than solar coronal loops.
The surprising finding, the team says, was the location of the flare. Contrary to our Sun, the site of the observed flare does not correspond to the detected spots [4].
"Interestingly, the flare occurs on a rather inconspicuous portion of the star's surface, away from the main concentration of activity in terms of dark spots," explains Wolter.
Speedy Mic is a very young star: with an age of only about 30 million years, it is roughly 150 times younger than the Sun. "It is very likely that our young Sun was a fast rotator as well," says Wolter. "Studying Speedy Mic is thus like observing our own host star while still in its infancy. These studies may also contribute to the understanding of current solar eruptions which can cause havoc in our telecommunications and power distributions."
The team reports their results in the journal Astronomy and Astrophysics ("Doppler imaging an X-ray flare on the ultrafast rotator BO Mic - A contemporaneous multiwavelength study using XMM-Newton and VLT", by. U. Wolter et al.).
Notes
The team is composed of U. Wolter, J. Robrade, and J. Schmitt (Hamburg Observatory, Germany), and J. Ness (Arizona State University, USA).
BO Microscopii (or BO Mic and nicknamed 'Speedy Mic') is a young star with a mass about 90 % the mass of our Sun. It is located 150 light years away towards the Microscope constellation. Speedy Mic owns its name because of its very fast rotation: it completes a full turn in about 9 hours. The object rotates thus 66 times as fast as our Sun, which results in much stronger magnetic fields than on the Sun.
Speedy Mic is a star slightly smaller than the Sun and is about ten million times further away from us than the Sun. Trying to see spots on its surface is thus as challenging as trying to directly obtain a photograph of the footsteps of Neil Armstrong on the Moon, and be able to see details in it. This is impossible to achieve even with the best telescopes: to obtain an image with such amount of details, you would need a telescope with a 400 km wide mirror! Astronomers make therefore use of indirect imaging techniques, such as Doppler imaging, to achieve this incredible prowess. Doppler imaging makes use of the information contained in the slightly changing spectra observed as a star rotates. In this case, the astronomers obtained 142 spectra of the star with the UVES spectrograph on ESO's VLT.
Sunspots, which are cooler, but still very hot regions of the Sun's surface, are known to be regions of intense magnetic activity.
Adapted from materials provided by ESO.

Fausto Intilla

www.oloscience.com

Supercomputers Offer New Explanation Of Tunguska Disaster

Source:

http://www.sciencedaily.com/releases/2007/12/071218122415.htm

ScienceDaily (Dec. 19, 2007) — The stunning amount of forest devastation at Tunguska a century ago in Siberia may have been caused by an asteroid only a fraction as large as previously published estimates, Sandia National Laboratories supercomputer simulations suggest.

“The asteroid that caused the extensive damage was much smaller than we had thought,” says Sandia principal investigator Mark Boslough of the impact that occurred June 30, 1908. “That such a small object can do this kind of destruction suggests that smaller asteroids are something to consider. Their smaller size indicates such collisions are not as improbable as we had believed.”
Because smaller asteroids approach Earth statistically more frequently than larger ones, he says, “We should be making more efforts at detecting the smaller ones than we have till now.”
The new simulation — which more closely matches the widely known facts of destruction than earlier models — shows that the center of mass of an asteroid exploding above the ground is transported downward at speeds faster than sound. It takes the form of a high-temperature jet of expanding gas called a fireball.
This causes stronger blast waves and thermal radiation pulses at the surface than would be predicted by an explosion limited to the height at which the blast was initiated.
“Our understanding was oversimplified,” says Boslough, “We no longer have to make the same simplifying assumptions, because present-day supercomputers allow us to do things with high resolution in 3-D. Everything gets clearer as you look at things with more refined tools.”
The new interpretation also accounts for the fact that winds were amplified above ridgelines where trees tended to be blown down, and that the forest at the time of the explosion, according to foresters, was not healthy. Thus previous scientific estimates had overstated the devastation caused by the asteroid, since topographic and ecologic factors contributing to the result had not been taken into account.
“There’s actually less devastation than previously thought,” says Boslough, “but it was caused by a far smaller asteroid. Unfortunately, it’s not a complete wash in terms of the potential hazard, because there are more smaller asteroids than larger ones.”
Boslough and colleagues achieved fame more than a decade ago by accurately predicting that that the fireball caused by the intersection of the comet Shoemaker-Levy 9 with Jupiter would be observable from Earth.
Simulations show that the material of an incoming asteroid is compressed by the increasing resistance of Earth’s atmosphere. As it penetrates deeper, the more and more resistant atmospheric wall causes it to explode as an airburst that precipitates the downward flow of heated gas.
Because of the additional energy transported toward the surface by the fireball, what scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons. The physical size of the asteroid, says Boslough, depends upon its speed and whether it is porous or nonporous, icy or waterless, and other material characteristics.
“Any strategy for defense or deflection should take into consideration this revised understanding of the mechanism of explosion,” says Boslough.
One of most prominent papers in estimating frequency of impact was published five years ago in Nature by Sandia researcher Dick Spalding and his colleagues, from satellite data on explosions in atmosphere. “They can count those events and estimate frequencies of arrival through probabilistic arguments,” says Boslough.
The work was presented at the American Geophysical Union meeting in San Francisco on Dec. 11. A paper on the phenomenon, co-authored by Sandia researcher Dave Crawford and entitled “Low–altitude airbursts and the impact threat” has been accepted for publication in the International Journal of Impact Engineering.
The research was paid for by Sandia’s Laboratory-Directed Research and Development office.
Adapted from materials provided by DOE/Sandia National Laboratories.

Fausto Intilla

www.oloscience.com

Black Hole Fires At Neighboring Galaxy

Source:

http://www.sciencedaily.com/releases/2007/12/071218103611.htm

ScienceDaily (Dec. 18, 2007) — A jet from a black hole at the center of a galaxy strikes the edge of another galaxy. This is the first time such an interaction has been found. The jet impacts the companion galaxy at its edge and is then disrupted and deflected, much like how a stream of water from a hose will splay out after hitting a wall at an angle.

Each wavelength shows a different aspect of this system, known as 3C321. The Chandra X-ray image provides evidence that each galaxy contains a rapidly growing supermassive black hole at its center. The glow from the stars in each galaxy can be detected from Hubble's optical light images (not shown).
A bright spot in the VLA and MERLIN radio image shows where the jet has struck the side of the galaxy - about 20,000 light years from the main galaxy - dissipating some of its energy. An even larger "hotspot" of radio emission detected by VLA reveals that the jet terminates much farther away from the galaxy, at a distance of about 850,000 light years away.
Large quantities of warm and hot gas could be detected in the vicinity of the galaxies, indicating the supermassive black holes in both galaxies have had a violent past. Faint emission from Chandra, Hubble and Spitzer, not shown in this image, indicate that the galaxies are orbiting in a clockwise direction, implying that the companion galaxy is swinging into the path of the jet.
Since the Chandra data shows that particle acceleration is still occurring in this hotspot, the jet must have struck the companion galaxy relatively recently, less than about a million years ago (i.e. less than the light travel time to the hotspot). This relatively short cosmic time frame makes this event a very rare phenomenon.
This "death star galaxy" will produce large amounts of high-energy radiation, which may cause severe damage to the atmospheres of any planets in the companion galaxy that lie in the path of the jet.
From the Earth we look down the barrel of jets from supermassive black holes, however these so-called "blazars" are at much safer distances of millions or billions of light years.
Adapted from materials provided by Chandra X-ray Observatory.

Fausto Intilla

www.oloscience.com

Largest Digital Survey Of The Milky Way Released

Source:

http://www.sciencedaily.com/releases/2007/12/071210112009.htm

ScienceDaily (Dec. 17, 2007) — A collaboration of over 50 astronomers, The IPHAS consortium, led from the UK, with partners in Europe, USA, Australia, has released today (10th December 2007) the first comprehensive optical digital survey of our own Milky Way. Conducted by looking at light emitted by hydrogen ions, using the Isaac Newton Telescope on La Palma, the survey contains stunning red images of nebulae and stars.

To date, the IPHAS survey includes some 200 million unique objects in the newly released catalogue. This immense resource will foster studies that can be at once both comprehensive and subtle, of the stellar demographics of the Milky Way and of its three-dimensional structure.
Professor Janet Drew of the University of Hertfordshire said "Using the distinctive Hydrogen marker we are able to look at some of the least understood stars in the Galaxy -- those at the early and very late stages of their life cycles. These represent less than one in a thousand stars, so the IPHAS data will greatly improve our picture of stellar evolution."
IPHAS is embracing a recent change in the way astronomers share data. As well as being available through traditional web access it is also being published through a Virtual Observatory interface, where it can automatically be cross-referenced with other relevant data catalogues.
Dr Nic Walton of the University of Cambridge said "Using the standard Virtual Observatory interface is a very effective way of exploiting the IPHAS survey data. This is a substantial and significant survey, which aims to eventually contain 7-800 million objects. Access through the AstroGrid Virtual Observatory opens up a full range of analysis options and should allow astronomers to make greater use of the information. IPHAS is the largest dataset published primarily through Virtual Observatory interfaces to date, and as such heralds the future of survey data mining."
This initial data release is of observations of the Northern Plane of the Milky Way (the star filled section) that cover 1600 sq deg, in two broadband colours, and a narrow band filter sensitive to the emission of Hydrogen in the red part of the spectrum (H-alpha emission). The image resolution is high enough to permit the detection of individual stars exhibiting H-alpha emission, in addition to the diffuse gas that makes up the often-beautiful glowing nebulae that lower spatial resolution surveys have made known to us before.
The IPHAS database is already revealing a wealth of new science. For example, IPHAS team members from the University of Southampton, have led an effort to extract and catalogue the brighter H-alpha emission line stars revealed so far by the survey. This list of nearly 5000 objects is already the longest single list of its kind. The distribution of these special objects, across the northern sky, traces 'hot spots' of recently formed stars in our Galaxy much more convincingly than has been possible hitherto.
The IPHAS survey will eventually be extended to cover the entire galactic plane of our galaxy, with a coverage approaching 4000 square degrees (for comparison, the moon on the sky as seen from Earth covers ~0.1 square degrees).
The data is described in a paper submitted to the Monthly Notices of the Royal Astronomical Society.
Adapted from materials provided by Science and Technology Facilities Council.

Fausto Intilla

www.oloscience.com

Deep Impact Spacecraft Heads For Comet Hartley 2

Source:

http://www.sciencedaily.com/releases/2007/12/071215203737.htm

ScienceDaily (Dec. 16, 2007) — NASA has given a University of Maryland-led team of scientists the green light to fly the Deep Impact spacecraft to Comet Hartley 2 on a two-part extended mission known as EPOXI. The spacecraft will fly by Earth on New Year's Eve at the beginning of a more than two-and-a-half-year journey to Hartley 2.

The EPOXI mission is actually two new missions in one. During the first six months of the journey to Hartley 2, the Extrasolar Planet Observations and Characterization (EPOCh) mission will use the larger of the two telescopes on the Deep Impact spacecraft to search for Earth-sized planets around five stars selected as likely candidates for such planets. Upon arriving at the comet the Deep Impact eXtended Investigation (DIXI) will conduct an extended flyby of Hartley 2 using all three of the spacecraft's instruments (two telescopes with digital color cameras and an infrared spectrometer).
"It's exciting that we can send the Deep Impact spacecraft on a new mission that combines two totally independent science investigations, both of which can help us better understand how solar systems form and evolve," said Deep Impact leader and University of Maryland astronomer Michael A'Hearn, who is principal investigator (PI) for both the overall EPOXI mission and its DIXI component.
The EPOXI mission brings back the Deep Impact partnership between the University of Maryland, NASA's Jet Propulsion Laboratory (JPL) and Ball Aerospace & Technologies Corporation, and adds NASA's Goddard Space Flight Center.
Daughters of Deep Impact
On July 4th 2005, the University of Maryland-led NASA mission Deep Impact made history and world-wide headlines when it smashed a probe into Comet Tempel. The mission yielded a wealth of new cometary information, but the data on Tempel 1 was in many cases startlingly different from that from comet missions Deep Space 1 and Stardust. As a result, rather than revealing the true nature of comets, the sometimes conflicting data from these three missions has left scientists questioning most of what they thought they knew about these fascinating, and potentially dangerous, objects; and longing for new data from other comets.
"One of the great surprises of comet explorations has been the wide diversity among the different cometary surfaces imaged to date," said A'Hearn. "We want a close look at Hartley 2 to see if the surprises of Tempel 1 are more common than we thought, or if Tempel 1 really is unusual."
After the completion of Deep Impact, the mission team knew they had a still healthy and flight-proven spacecraft that was capable of traveling to a never-before-visited comet at a fraction of the cost of a newly built and launched mission. In 2006 the A'Hearn-led team began the proposal process that eventually became EPOXI.
Trajectory of a dual mission
When the Deep Impact/EPOXI spacecraft passes by Earth on December 31, 2007, it will use the pull of our planet's gravity to direct and speed itself toward comet Hartley 2. In doing this the spacecraft is aimed toward an encounter with comet Hartley 2 at a time when tracking stations in two different locations on Earth can "see" the spacecraft to receive data from it and send commands to it. In late December 2007, the spacecraft's instruments will be recalibrated using the Moon as a target.
Hartley 2 was not the original destination of the new mission. It was selected in October following the surprising realization that despite tremendous efforts by many observatories and observers, the scientists could not reliably identify their first choice, comet Boethin, and its orbit in time to plan the mission flyby of Earth. The team then recommended to NASA that it be allowed to fly to the backup target, comet Hartley 2.
"Hartley 2 is scientifically just as interesting as comet Boethin since both have relatively small, active nuclei," said A'Hearn. "As we have worked the details of the comet Hartley 2 encounter, we are confident that the observations will turn out to be even better than Boethin."
The journey's EPOCh leg
The first part of the Deep Impact extended mission -- the search for alien worlds -- will begin in late January as the spacecraft cruises toward Hartley 2. More than 200 alien (extrasolar) planets have been discovered to date. Most of these are detected indirectly, by the gravitational pull they exert on their parent star. Directly observing extrasolar planets by detecting the light reflected from them is very difficult, because a star's brilliance obscures light coming from any planets orbiting it.
However, sometimes the orbit of an extrasolar world is aligned so that it eclipses its star as seen from Earth. In these rare cases, light from that planet can be seen directly.
"When the planet appears next to its star, your telescope captures their combined light. When the planet passes behind its star, your telescope only sees light from the star. By subtracting light from just the star from the combined light, you are left with light from the planet,” said Goddard scientist Drake Deming, who heads EPOCh and is deputy principal investigator for EPOXI. "We can analyze this light to discover what the atmospheres of these planets are like."
Planets as small as three Earth masses can be detected in this way. EPOCh will also observe the Earth in visible and infrared wavelengths to allow comparisons with future discoveries of Earth-like planets around other stars.
The mission will observe five nearby stars with "transiting extrasolar planets," so named because the planet transits, or passes in front of, its star. The planets were discovered earlier and are giant planets with massive atmospheres, like Jupiter in our solar system. They orbit their stars much closer than Earth does the sun, so they are hot and belong to the class of extrasolar planets nicknamed "Hot Jupiters."
However, these giant planets may not be alone. If there are other worlds around these stars, they might also transit the star and be discovered by the spacecraft. Even if they don't transit, Deep Impact could find them indirectly. Their gravity will pull on the transit planets, altering their orbits and the timing of their transits.
"Since Deep Impact will be able to stare at these stars for long periods, we can observe multiple transits and compare the timing to see if there are any hidden worlds," said Deming.
Are we there yet?
In June of 2008, the extended mission will end its EPOCh portion and transition to a long, quiet journey to comet Hartley 2. The total trip -- measured from its December 31, 2007 flyby of Earth to its closest encounter with the comet on October 11, 2010 -- will be roughly 1.6 billion miles or some 18 times the distance from the Earth to the sun. It will take the spacecraft three trips around the sun before it can intercept the comet, which at that time will be at a distance of some 12.4 million miles from Earth.
At the nearest point of its flyby of Hartley 2, the spacecraft will be some 550 miles from the comet. Deep Impact does not have another probe, so Hartley 2 will not get hit, but the close-up view will allow the spacecraft's two telescopes to closely observe surface features of the comet while its infrared spectrometer maps the composition of any outbursts of gas from the surface.
Comet science goals for this phase of the mission are to:
Search for and, if found, produce maps of outbursts of gas from the surface of comet Hartley 2. Track the outburst as the comet rotates. Correlate outbursts with surface features. Such outbursts were observed during the spacecraft's flyby of comet Tempel 1.
Obtain infrared spectral maps of gasses in the innermost portion of the coma. The coma is the cloud of gas and dust that surrounds the comet. Investigate the distribution of dust and gas in the coma.
Search for frozen volatiles (SUCH AS?) on the surface of the comet. Water ice, for example, was discovered when the flyby explored Tempel 1.
Produce broad band images of the comet that will establish limits on the size of the nucleus. Produce a model of its shape.
Map the brightness and color variations of the surface. Locate landscape features that indicate the processes by which the comet was formed. Compare the distribution of crater sizes with the distribution of the size of craters on other comets, asteroids and planetary satellites.
Map the temperature of the surface to assess how readily heat is transmitted to the interior and the flow of subsurface volatiles, such as water vapor, to the surface.
For A'Hearn and his DIXI team the most rewarding time will come after the flyby, as they turn the raw data into new insights on the structure and formation of comets and their place in the history of our solar system.
Adapted from materials provided by University of Maryland, College Park.

Fausto Intilla

www.oloscience.com

Gliese 581: Extrasolar Planet Might Indeed Be Habitable

Source:

http://www.sciencedaily.com/releases/2007/12/071213101403.htm

ScienceDaily (Dec. 14, 2007) — In April, a European team of astronomers announced the discovery of two possibly habitable Earth-like planets. Two new detailed studies of this system confirm that one of the planets might indeed be located within the habitable zone around the star Gliese 581.

More than 10 years after the discovery of the first extrasolar planet, astronomers have now discovered more than 250 of these planets. Until a few years ago, most of the newly discovered exoplanets were Jupiter-mass, probably gaseous, planets. Recently, astronomers have announced the discovery of several planets that are potentially much smaller, with a minimum mass lower than 10 Earth masses, what are now called super-Earths [1].
In April, a European team announced in Astronomy & Astrophysics the discovery of two new planets orbiting the M star Gliese 581 (a red dwarf), with masses of at least 5 and 8 Earth masses. Given their distance to their parent star, these new planets (now known as Gliese 581c and Gliese 581d) were the first ever possible candidates for habitable planets.
Contrary to Jupiter-like giant planets that are mainly gaseous, terrestrial planets are expected to be extremely diverse: some will be dry and airless, while others will have much more water and gases than the Earth. Only the next generation of telescopes will allow us to tell what these new worlds and their atmospheres are made of and to search for possible indications of life on these planets. However, theoretical investigations are possible today and can be a great help in identifying targets for these future observations.
In this framework, Astronomy & Astrophysics now publishes two theoretical studies of the Gliese 581 planetary system. Two international teams, one led by Franck Selsis [2] and the other by Werner von Bloh [3], investigate the possible habitability of these two super-Earths from two different points of view. To do so, they estimate the boundaries of the habitable zone around Gliese 581, that is, how close and how far from this star liquid water can exist on the surface of a planet.
F. Selsis and his colleagues compute the properties of a planet’s atmosphere at various distances from the star. If the planet is too close to the star, the water reservoir is vaporized, so Earth-like life forms cannot exist. The outer boundary corresponds to the distance where gaseous CO2 becomes unable to produce the strong greenhouse effect required to warm a planetary surface above the freezing point of water. The major uncertainty for the precise location of the habitable zone boundaries comes from clouds that cannot currently be modeled in detail. These limitations also occur when one looks at the Sun’s case: climate studies indicate that the inner boundary is located somewhere between 0.7 and 0.9 AU, and the outer limit is between 1.7 and 2.4 AU. Figure 1 illustrates the Sun’s habitable zone boundaries, compared to the case for Gliese 581 as computed both by Selsis and von Bloh.
W. von Bloh and his colleagues study a narrower region of the habitable zone where Earth-like photosynthesis is possible. This photosynthetic biomass production depends on the atmospheric CO2 concentration, as much as on the presence of liquid water on the planet. Using a thermal evolution model for the super-Earths, they have computed the sources of atmospheric CO2 (released through ridges and volcanoes) and its sinks (the consumption of gaseous CO2 by weathering processes). The main aspect of their model is the persistent balance (that exists on Earth) between the sink of CO2 in the atmosphere-ocean system and its release through plate-tectonics. In this model, the ability to sustain a photosynthetic biosphere strongly depends on the age of the planet, because a too old planet might not be active anymore, that is, would not release enough gaseous CO2. In this case, the planet would no longer be habitable. To compute the boundaries of the habitable zone as illustrated by Figure 1, von Bloh assumed a CO2 level of 10 bars.
The image above illustrates the boundary of the habitable zone as computed using both models and, for comparison, the boundary of the Sun’s habitable zone. Both teams found that, while Gliese 581 c is too close to the star to be habitable, the planet Gliese 581 d might be habitable. However, the environmental conditions on planet d might be too harsh to allow complex life to appear. Planet d is tidally locked, like the Moon in our Earth-Moon system, meaning that one side of the planet is permanently dark. Thus, strong winds may be caused by the temperature difference between the day and night sides of the planet. Since the planet is located at the outer edge of the habitable zone, life forms would have to grow with reduced stellar irradiation and a very peculiar climate.
This image also illustrates that the distances of planets c and d to the central star has strong variations due to the eccentricity of their orbits. In addition, being close to the star, their orbital periods are short: 12.9 days for planet c and 83.6 days for planet d. Figure 1 shows that planet d might temporarily leave and re-enter the habitable zone during its journey. However, even under these strange conditions, it might still be habitable if its atmosphere is dense enough. In any case, habitable conditions on planet d should be very different from what we encounter on Earth.
Last but not least, the possible habitability of one of these planets is particularly interesting because of the central star, which is a red dwarf, M-type star. About 75% of all stars in this Galaxy are M stars. They are long-lived (potentially tens of billion years), stable, and burn hydrogen. M stars have long been considered as poor candidates for harboring habitable planets: first because planets located in the habitable zone of M stars are tidally locked, with a permanent dark side, where the atmosphere is likely to condense irreversibly. Second, M stars have an intense magnetic activity, associated with violent flares and high X and extreme UV fluxes, during their early stage that might erode planetary atmospheres. Theoretical studies have recently shown that the environment of M stars might not prevent these planets from harboring life. M stars have then become very interesting for astronomers because habitable planets orbiting them are easier to detect via the radial-velocity and transit techniques than habitable planets around Sun-like stars.
Both studies definitely confirm that Gliese 581c and Gliese 581d will be prime targets for the future ESA/NASA space mission Darwin/Terrestrial Planet Finder (TPF), dedicated to the search for life on Earth-like planets. These space observatories will make it possible to determine the properties of their atmospheres.
A third paper on the Gliese 581 planetary system has recently been accepted for publication in Astronomy & Astrophysics. In this paper, H. Beust and his team [4] study the dynamical stability of the Gliese 581 planetary system. Such studies are very interesting in the framework of the potential habitability of these planets because the long-term evolution of the planetary orbits may regulate the climate of these planets. Mutual gravitational perturbations between different planets are present in any planetary system with more than one planet.
In our solar system, under the influence of the other planets, the Earth's orbit periodically evolves from purely circular to slightly eccentric. This is actually enough to trigger the alternance of warm and glacial eras. More drastic orbital changes could well have prevented the development of life. Beust and his colleagues computed the orbits of the Gliese 581 system over 100 Myr and find that the system appears dynamically stable, showing periodic orbital changes that are comparable to those of the Earth. The climate on the planets is expected to be stable, so it at least does not prevent life from developing, although it does not prove it happened either.
Notes
[1] The expression “super-Earths”, which is often used to refer to exoplanets between 2 and 10 Earth masses, might be confusing, as it suggests indeed that these planets are rocky planets that differ from the Earth only by their mass. But Gliese 581 c and d could very well be big icy planets, with a very different composition from the Earth.
[2] The team led by F. Selsis (CRAL and LAB, France) includes J.F. Kasting (Penn State Univ., USA), B. Levrard (IMCCE, France), J. Paillet (ESTEC, The Netherlands), I. Ribas (CSIC-IEEC, Spain), and X. Delfosse (LAOG, France).
[3] The team led by W. von Bloh (PIK, Germany) includes C. Bounama, S. Franck (PIK, Germany), and M. Cuntz (UTA, USA).
[4] The team led by H. Beust (LAOG, France) includes X. Bonfils (CAAUL, Portugal), X. Delfosse (LAOG, France), and S. Udry (Observatoire de Genève, Switzerland).
Journal references
The habitability of super-Earths in Gliese 581, by W. von Bloh, C. Bounama, M. Cuntz, and S. Franck. Astronomy & Astrophysics, 2007, vol. 476, p. 1365.
Habitable planets around the star Gliese 581?, by F. Selsis, J.F. Kasting, B. Levrard, J. Paillet, I. Ribas, and X. Delfosse. Astronomy & Astrophysics, 2007, vol. 476, p. 1373.
Dynamical evolution of the Gliese 581 planetary system, by H. Beust, X. Bonfils, X. Delfosse, and S. Udry. To be published in Astronomy & Astrophysics, 2008.
Adapted from materials provided by Astronomy & Astrophysics.

Fausto Intilla

www.oloscience.com

Jupiter's Moon Europa: What Could Be Under The Ice?

Source:

http://www.sciencedaily.com/releases/2007/12/071213180823.htm

ScienceDaily (Dec. 14, 2007) — Jupiter’s moon Europa is just as far away as ever, but new research is bringing scientists closer to being able to explore its tantalizing ice-covered ocean and determine its potential for harboring life.

“We’ve learned a lot about Europa in the past few years,” says William McKinnon, professor of Earth and Planetary Sciences at Washington University in St. Louis, Mo.
“Before we were almost sure that there was an ocean, but now the scientific community has come to a consensus that there most certainly is an ocean. We’re ready to take the next step and explore that ocean and the ice shell that overlays it. We have a number of new discoveries and techniques that can help us do that.”
McKinnon is discussing some of these recent findings and new opportunities for exploring Europa in a news briefing today at the meeting of the American Geophysical Union in San Francisco. He is joined by colleagues Donald Blankenship, research scientist at the Institute for Geophysics at the University of Texas at Austin’s Jackson School of Geosciences., and Peter Doran, associate professor of Earth and Environmental Sciences, University of Illinois at Chicago.
McKinnon points to refined methods that can use combined measurements of gravity and the magnetic field made from orbit to characterize Europa's ocean. By observing how the moon flexes and deforms and by measuring magnetic variations, researchers can determine how thick or thin the ice is over the ocean and even learn how salty the ocean is. A new model shows that radiation on Europa is much less, up to two-thirds less, than previous models predicted, making the environment much more hospitable for orbiting spacecraft or landers to operate.
Sophisticated reprocessing of data from the Galileo mission has revealed new information about the chemistry of Europa’s surface. It maps the presence of carbon dioxide, an important chemical for life, most probably coming from the ocean beneath the surface. This indicates that improved measurements from orbit have the chance to detect compounds not found in the Galileo data.
Future explorations of Europa will benefit from lessons learned from the Cassini spacecraft’s recent findings of active geysers on Saturn’s moon Enceladus. “Europa is a young, geologically active body like Enceladus,” says McKinnon. Galileo didn’t see any plumes on Europa like those spouting from Enceladus, but it didn’t have the best instrumentation to detect the telltale hot spots. “Now we know what we should look for,” says McKinnon, “and we should expect the unexpected.”
New radar sounding techniques will be a key component for exploring Europa. “There have been theories about whether the ice above the ocean is thick or thin, and now we have the ability to determine this with radar,” says Blankenship. “That’s been proved by the radar on Mars Express, which imaged the north polar cap of Mars, and the higher-resolution radar on the Mars Reconnaissance Orbiter. Radar can give us a detailed cross section through the ice shell on Europa.” The ice-penetrating radar will also be able to locate liquid water both within and beneath the shell, he continues, just as it can spot water within crevasses and lakes beneath the ice of Antarctica. "Free water within the icy shell and its relationship to the underlying ocean will be a critical factor in determining the habitability of Europa."
Researchers are also preparing for the day in the future when they will be able to get to Europa's surface and ultimately into its ocean to explore it directly. "In the meantime, we're using extreme environments on Earth as our laboratory," says Doran. "Ice-covered lakes in Antarctica are good, small-scale analogs to what we might find on Europa." Doran is lead investigator of a project called Endurance, which, in collaboration with Stone Aerospace, is developing an autonomous underwater robotic vehicle, to test approaches and procedures for exploring Europa's ocean. The project is funded by NASA's Astrobiology Science and Technology for Exploring Planets program.
"We're testing the vehicle in Wisconsin in February 2008," Doran says, "and then we'll be deploying it in Antarctica later in the year." The robotic explorer will be able to create three-dimensional maps of the subsurface Antarctic lake. It will also be able to map the biochemistry of the water body, pinpointing the chemical signatures that may indicate life.
For Europa, under-ice exploration lies in the distant future. In the meantime, say the researchers, a closer look at Europa is possible from an orbiting spacecraft able to measure gravity and magnetic fields, determine surface composition, search for active or recent eruptions, and use radar to understand the relationship between the surface and the sub-surface.
Adapted from materials provided by University of Texas at Austin.

Fausto Intilla

www.oloscience.com

Saturn's Rings May Be As Old As Solar System

Source:

http://www.sciencedaily.com/releases/2007/12/071213101426.htm

ScienceDaily (Dec. 13, 2007) — New observations by NASA's Cassini spacecraft indicate the rings of Saturn, once thought to have formed during the age of the dinosaurs, instead may have been created roughly 4.5 billion years ago when the solar system was still under construction.

Professor Larry Esposito, principal investigator for Cassini's Ultraviolet Imaging Spectrograph at CU-Boulder, said data from NASA's Voyager spacecraft in the 1970s and later NASA's Hubble Space Telescope had led scientists to believe Saturn's rings were relatively youthful and likely created by a comet that shattered a large moon, perhaps 100 million years ago.
But ring features seen by instruments on Cassini -- which arrived at Saturn in 2004 -- indicate the rings were not formed by a single cataclysmic event, he said. The ages of the different rings appear to vary significantly and the ring material is continually being recycled, Esposito said.
"The evidence is consistent with the picture that Saturn has had rings all through its history," said Esposito of CU-Boulder's Laboratory for Atmospheric and Space Physics. "We see extensive, rapid recycling of ring material, in which moons are continually shattered into ring particles, which then gather together and re-form moons."
"We have discovered that the rings were probably not created just yesterday in cosmic time, and in this scenario it is not just luck that we are seeing planetary rings now," said Esposito. "They probably were always around but continually changing, and they will be around for many billions of years."
Scientists had previously believed rings as old as Saturn itself should be darker due to ongoing pollution by the "infall" of meteoric dust, leaving telltale spectral signatures, Esposito said. But the new Cassini observations indicate the churning mass of ice and rock within Saturn's gigantic ring system is likely much larger than previously estimated, helping to explain why the rings appear relatively bright to ground-based telescopes and spacecraft.
"The more mass there is in the rings, the more raw material there is for recycling, which essentially spreads this cosmic pollution around," he said. "If this pollution is being shared by a much larger volume of ring material, it becomes diluted and helps explain why the rings appear brighter and more pristine than we would have expected."
Esposito, who discovered Saturn's faint F ring in 1979 using data from NASA's Pioneer 11 spacecraft, said an upcoming paper by him and colleagues in the journal Icarus supports the theory that Saturn's ring material is being continually recycled. Observing the flickering of starlight passing through the rings in a process known as stellar occultation, the researchers discovered 13 objects in the F ring ranging in size from 30 yards to six miles across.
Since most of the objects were translucent -- indicating at least some starlight was passing through them -- the researchers concluded they probably are temporary clumps of icy boulders that are continually collecting and disbanding due to the competing processes of shattering and coming together again. The team tagged the clumpy moonlets with cat names like "Mittens" and "Fluffy" because they appear to come and go unexpectedly over time and have multiple lives, said Esposito.
Esposito stressed that in the future Saturn's rings won't be the same we see today, likening them to great cities around the world like San Francisco, Berlin or Beijing. "While the cities themselves will go on for centuries or millennia, the faces of people on the streets will always be changing due to continual birth and aging of new citizens."
Esposito and CU-Boulder colleague Miodrag Sremcevic presented their findings December 13 in a news briefing at the fall meeting of the American Geophysical Union held Dec. 10 to Dec. 14 in San Francisco.
Adapted from materials provided by University of Colorado at Boulder.

Fausto Intilla

www.oloscience.com

Hazy Red Sunset On Extrasolar Planet

Source:

http://www.sciencedaily.com/releases/2007/12/071211094914.htm

ScienceDaily (Dec. 12, 2007) — A team of astronomers have used the NASA/ESA Hubble Space Telescope to detect, for the first time, strong evidence of hazes in the atmosphere of a planet orbiting a distant star. The discovery comes after extensive observations made recently with Hubble's Advanced Camera for Surveys (ACS).

The team, led by Frédéric Pont from the Geneva University Observatory in Switzerland, used Hubble's ACS to make the first detection of hazes in the atmosphere of the giant planet. "One of the long-term goals of studying extrasolar planets is to measure the atmosphere of an Earth-like planet, this present result is a step in this direction" says Pont. "HD 189733b is the first extrasolar planet for which we are piecing together a complete idea of what it really looks like."
The new observations were made as the extrasolar planet, dubbed HD 189733b, passed in front of its parent star in a transit. As the light from the star passes through the atmosphere around the limb of the giant extrasolar planet, the gases in the atmosphere stamp their unique signature on the starlight from HD 189733.
The planet itself, orbiting close to its parent star, is a 'hot-Jupiter' type of gas giant slightly larger than Jupiter. The proximity to its star results in an atmospheric temperature of roughly seven hundred degrees Celsius. Measurements of the way light varies as the planet passes in front of its parent star indicates that HD 189733b has neither Earth-sized moons nor any discernable Saturn-like ring system.
Hubble's ACS camera, coupled with a grism (a kind of cross between a prism and a diffraction grating) allowed the astronomers to make extremely accurate measurements of the spectrum of HD 189733b, allowing conclusions to be drawn about the composition of the planet's atmosphere. The exquisite level of precision needed to make this observation can only, at the moment, be achieved from space. The combination of a large planet and relatively small parent star -- only 76% of the diameter of our Sun -- contributes to the success of this delicate experiment.
Where the scientists had expected to see the fingerprints of sodium, potassium and water there were none. This finding, combined with the distinct shape of the planet's spectrum, infers that high level hazes (with an altitude range of roughly 1000 km) are present. So the atmosphere on HD 189733b would look very similar to a gorgeous red sunset over Athens! Venus and Saturn's moon Titan, in our own Solar System, are also covered with haze. According to the scientists the haze probably consists of tiny particles (less than 1/1000 mm in size) of condensates of iron, silicates and aluminium oxide dust (the compound on Earth which the mineral sapphire is made of).
As part of the observations of HD 189733, the teams of astronomers also needed to accurately account for the variations in the star's brightness during the set of observations. 'Starspots' like those seen on our own Sun may cover several percent of the star and are thought to be about 1000 degrees Celsius cooler than the rest of HD 189733's surface. It was found that there is a starspot on the star's surface which is over 80,000 km across.
Adapted from materials provided by ESA/Hubble Information Centre.

Fausto Intilla

www.oloscience.com

Building Blocks Of Life Formed On Mars, Scientists Conclude

Source:

http://www.sciencedaily.com/releases/2007/12/071211095141.htm

ScienceDaily (Dec. 12, 2007) — Organic compounds contain carbon and hydrogen and form the building blocks of all life on Earth. By analyzing organic material and minerals in the Martian meteorite Allan Hills 84001, scientists at the Carnegie Institution's Geophysical Laboratory have shown for the first time that building blocks of life formed on Mars early in its history. Previously, scientists have thought that organic material in ALH 84001 was brought to Mars by meteorite impacts or more speculatively originated from ancient Martian microbes.

The Carnegie-led team made a comprehensive study of the ALH 84001 meteorite and compared the results with data from related rocks found on Svalbard, Norway. The Svalbard samples occur in volcanoes that erupted in a freezing Arctic climate about 1 million years ago—possibly mimicking conditions on early Mars.
“Organic material occurs within tiny spheres of carbonate minerals in both the Martian and Earth rocks,” explained Andrew Steele, lead author of the study. “We found that the organic material is closely associated with the iron oxide mineral magnetite, which is the key to understanding how these compounds formed.”
The organic material in the rocks from Svalbard formed when volcanoes erupted under freezing conditions. During cooling, magnetite acted as a catalyst to form organic compounds from fluids rich in carbon dioxide (CO2) and water (H2O). This event occurred under conditions where no forms of life are likely to exist. The similar association of carbonate, magnetite and organic material in the Martian meteorite ALH 84001 is very compelling and shows that the organic material did not originate from Martian life forms but formed directly from chemical reactions within the rock. This is the first study to show that Mars is capable of forming organic compounds at all.
The organic material in the Allan Hills meteorite may have formed during two different events. The first, similar to the Svalbard samples, was during rapid cooling of fluids on Mars. A second event produced organic material from carbonate minerals during impact ejection of ALH 84001 from Mars.
“The results of this study show that volcanic activity in a freezing climate can produce organic compounds,” remarked co-author Hans E.F. Amundsen from Earth and Planetary Exploration Services. “This implies that building blocks of life can form on cold rocky planets throughout the Universe.”
“Our finding sets the stage for the Mars Science Laboratory (MSL) mission in 2009,” remarked Steele, who is a member of the Sample Analysis on Mars (SAM) instrument team onboard MSL. “We now know that Mars can produce organic compounds. Part of the mission's goal is to identify organic compounds, their sources, and to detect molecules relevant to life. We know that they are there. We just have to find them.”
The research is published in Meteoritics & Planetary Science http://meteoritics.org/index.htm
For more information on the MSL mission and the SAM instrument see http://mars.jpl.nasa.gov/msl/ and http://ael.gsfc.nasa.gov/marsSAM.shtml
This research was funded by NASA SRLIDA, ASTEP, NAI and ASTID programs; the Marshall Scholarship program; and the University of Oxford, Earth Sciences Department and was carried out in collaboration with the Arctic Mars Analog Svalbard Expedition (AMASE) project.
Adapted from materials provided by Carnegie Institution for Science.

Fausto Intilla

www.oloscience.com

Plasma Science Instrument Finds Surprises At Solar System's Edge

Source:

http://www.sciencedaily.com/releases/2007/12/071210162949.htm

ScienceDaily (Dec. 11, 2007) — The Voyager 2 spacecraft's Plasma Science instrument, developed at MIT in the 1970s, has turned up surprising revelations about the boundary zone that marks the edge of the sun's influence in space.

The unexpected findings emerged in the last few weeks as the spacecraft traversed the termination shockwave formed when the flow of particles constantly streaming out from the sun--the solar wind--slams into the surrounding thin gas that fills the space between stars.
The first surprise is that there is an unexpectedly strong magnetic field in that surrounding interstellar region, generated by currents in that incredibly tenuous gas. This magnetic field is squashing the bubble of outflowing gas from the sun, distorting it from the uniform spherical shape space physicists had expected to find.
A second surprise also emerged from Voyager 2's passage through the solar system's outer edge: Just outside that boundary the temperature, although hotter than inside, was ten times cooler than expected. Theorists had to scramble to come up with an explanation for the unanticipated chilling effect.
"It's a different kind of shockwave than we've seen anywhere else," says John Richardson, principal investigator for the Plasma Physics instrument and a Principal Research Scientist at MIT's Kavli Institute for Astrophysics and Space Science. The unexpected coolness, theorists now think, is caused by energy going into particles that are hotter than those that can be measured by the MIT plasma instrument.
Richardson will be taking part in a press conference reporting the new findings on Monday, Dec. 10, at a meeting of the American Geophysical Union in San Francisco.
The Voyager 1 and 2 spacecraft were designed primarily to study the planets Jupiter and Saturn and their moons. After launch, Voyager 2's path was adjusted to take it past Uranus and Neptune as well. Although the craft were only built for a five-year mission, both are still working well three decades later.
"We were incredibly lucky to have it last 30 years," says John Belcher, professor of physics at MIT and former principal investigator for the Voyager Plasma Science instrument. The craft is now expected to keep working until about 2020, and still has important scientific objectives ahead.
It is now passing through a boundary zone called the heliosheath, a region where the solar wind interacts with the surrounding interstellar medium. But sometime in the next decade, it will cross a final edge, called the heliopause, where the sun's outflow of particles ends. At that point, it will be able to measure characteristics of the interstellar medium, for the first time, in a region unaffected by the solar wind and the sun's magnetism.
Although Voyager 1 had already crossed the termination shockwave three years ago, the MIT Plasma Science instrument on that spacecraft had stopped working, so the spacecraft could only indirectly detect the end of the sun's influence.
But with Voyager 2, the Plasma Science instrument not only detected the boundary, making detailed measurements of the solar wind's temperature, speed and density as the spacecraft crossed through it, but it actually encountered the shockwave repeatedly. Because the outflow of the solar wind varies with changes in the sun's activity level, building up during large solar flares and quieting during lulls in sunspot activity, the boundary itself pulsates in and out. These pulsations can wash across the craft multiple times, just as a boat landing onshore may cross the ocean's edge multiple times as waves crash in and then recede.
While Voyager 1 apparently made a single crossing, Voyager 2 apparently crossed the boundary five times, producing a wealth of new data. It's even possible that if there are large variations in that solar outflow, the shock layer "could push past Voyager again," says Richardson. "That would give us some idea of how elastic the shock is" -- that is, how far out these pulsations may stretch. Until and unless such detections are made, "we only have models" of how great such variations might be, he says.
Voyager 2 is now 7.879 billion miles from Earth, traveling away at almost 35,000 miles per hour. Voyager 1 is 9.797 billion miles away, going more than 38,000 mph.
The Plasma Science instrument was developed by the late Professor Herbert Bridge and Alan Lazarus, a senior research scientist in the Department of Physics and MIT's Kavli Institute for Astrophysics and Space Science. NASA has sponsored the work.
Adapted from materials provided by Massachusetts Institute of Technology.

Fausto Intilla

www.oloscience.com

Odd Little Star Has Magnetic Personality

Source:

http://www.sciencedaily.com/releases/2007/12/071205095342.htm

ScienceDaily (Dec. 6, 2007) — A dwarf star with a surprisingly magnetic personality and a huge hot spot covering half its surface area is showing astronomers that life as a cool dwarf is not necessarily as simple and quiet as they once assumed.

Simultaneous observations made by four of the most powerful Earth- and space-based telescopes revealed an unusually active magnetic field on the ultracool low-mass star TVLM513-46546. A team of astronomers, led by Dr. Edo Berger, a Carnegie-Princeton postdoctoral fellow at Princeton University, is using these observations to explain the flamboyant activity of this M-type dwarf that lies about 35 light-years away in the constellation Boötes.
The team’s observations of TVLM513-46546 combine radio data from the Very Large Array, optical spectra from the Gemini North 8-meter telescope, ultraviolet images from the orbiting Swift observatory and x-ray data from NASA’s Chandra X-ray Observatory. This is the first time that such a powerful set of telescopes has been trained on one of the smallest known stars. The study is part of a program that looks at the origins of magnetic fields in ultracool dwarfs, stars that astronomers always assumed were simple, quiet, and more tranquil than their hotter and more massive siblings.
“With such a unique set of observations you always expect to find the unexpected,” said Berger, “but we were shocked at the level of complexity that this object exhibits.”
The star’s steady radio emission is interrupted with spectacular fireworks displays of minute-long flares. These flares come from the catastrophic collisions and merging of the magnetic fields in the corona of the star; these actions drive the annihilation of magnetic energy like a giant short-circuits in the fields. The team also observed soft x-ray emission and an x-ray flare.
Also for the first time, the group charted optical hydrogen-alpha emission with a period of two hours that matches the two-hour rotation period of the star. “We find a hot spot that covers half of the surface of the star like a giant lighthouse that rotates in and out of our field of view,” said Berger. “We still do not know why only half of the star is lit up in hydrogen and if this situation remains unchanged over days, weeks, years, or centuries.”
Berger describes the dwarf star’s magnetic field as probably being a simple dipole (north-south orientation, like the Earth’s much weaker magnetic field) that extends out at least one stellar radius above the surface. There is also a smaller-scale field that has loops similar to those seen on the Sun, but smaller. “Those loops and arcs occur on random places on the surface of the star, “said Berger. “That’s where the flares originate that last only a few minutes, whereas the overall field doesn’t get disturbed.”
Objects like TVLM513-46546 were once thought to be models of stellar quiescence and simplicity, with little to no magnetic field activity. “Theory has always said that as we look at cooler and cooler stars, the coolest will be essentially dead,” said Berger. “It turns out that stars like TVLM513-46546 have very complex magnetic activity around them, activity more like our Sun than that of a star that is barely functional.”
This one’s complicated magnetic field environment and possible hot spot may indicate some unusual activity beneath the star’s surface (in its dynamo) or possibly even the existence of a still-hidden companion. The idea of an unseen companion as an explanation for the star’s excitable magnetic disposition is an intriguing one, says Berger, but no such object has yet been detected. “The main idea to consider here is an analogy to other systems where the presence of a companion directly or indirectly excites magnetic activity,” he said.
Like other ultracool dwarf stars, TVLM513-46546 is an M-type star with surface temperatures below about 2400K (2127 Celsius) and a mass of only 8 to 10% that of our Sun. By contrast, the Sun is a G-type star with an average surface temperature of 6000K (5727 Celsius).
Imagine the interior of the Sun layered like an onion. Its internal convection is the process by which heat from the nuclear fusion at the core is transported by large spinning currents that move through the Sun’s outer layers. Differential rotation is simply the term for the different spin rates of different layers. Together these motions of electrically charged gas spin up the magnetic field structures we see at the Sun.
By contrast, an ultracool M-type star like TVLM513-46546 is fully convective. That is, the zone that transports heat to the surface of the star extends all the way from the stellar surface into the center, like the bubble of a huge boiling pot. Such a simple structure has been predicted to generate a very basic magnetic field structure, perhaps more like the Earth’s than the complex fields we see on the Sun. Why TVLM513-46546 has such a complex field and activity remains to be studied.
In order to find out if this star is just a stellar oddity, or if it might turn out be a typical prototype of ultracool dwarfs, the research team plans to continue with observations of other such stars. The team expects the larger sample to show how other candidate low-mass stars (and brown dwarfs, objects too hot to be planets and too cool to be stars) generate magnetic fields. Berger also notes that he’d like to get more observations to try and spot any possible companions to such stars. “The issue of a possible companion is really pure speculation at this point,” he said. “However, I am trying to get observations that will assess this possibility.”
These results are being published in the February 10, 2008 issue of the Astrophysical Journal.
Partial studies of magnetic activity on these types of stars have been performed previously, but this is the first time that such a powerful set of telescopes has been simultaneously pointed at the same object.
Adapted from materials provided by Gemini Observatory.

Fausto Intilla

www.oloscience.com

Hinode Reveals New Insights About The Origin Of Solar Wind

Source:

http://www.sciencedaily.com/releases/2007/12/071206145256.htm

ScienceDaily (Dec. 7, 2007) — Images from telescopes aboard a Japanese satellite have shed new light about the sun's magnetic field and the origins of solar wind, which disrupts power grids, satellites and communications on Earth.

Many of Hinode's key goals involve understanding the basic physics that operate on the Sun, providing Earth with the heat and energy to sustain life.
The discoveries may also have a practical edge, since eruptions of magnetic energy from the Sun are responsible for "space weather" events that can threaten telecommunications, navigation systems and electric power grids on Earth. A better understanding of these eruptions and of the solar wind, the huge volume of ionized material that the Sun spews into interplanetary space, may help people predict or plan for space weather events.
Data from the Hinode satellite shows that magnetic waves play a critical role in driving the solar wind into space. The solar wind is a stream of electrically charged gas that is propelled away from the sun in all directions at speeds of almost 1 million miles per hour. Better understanding of the solar wind may lead to more accurate prediction of damaging radiation waves before they reach satellites.
How the solar wind is formed and powered has been the subject of debate for decades. Powerful magnetic Alfvén waves in the electrically charged gas near the sun have always been a leading candidate as a force in the formation of solar wind since Alfvén waves in principle can transfer energy from the sun's surface up through its atmosphere, or corona, into the solar wind.
In the solar atmosphere, Alfvén waves are created when convective motions and sound waves push magnetic fields around, or when dynamic processes create electrical currents that allow the magnetic fields to change shape or reconnect.
"Until now, Alfvén waves have been impossible to observe because of limited resolution of available instruments," said Alexei Pevtsov, Hinode program scientist, NASA Headquarters, Washington. "With the help of Hinode, we are now able to see direct evidence of Alfvén waves, which will help us unravel the mystery of how the solar wind is powered."
Using Hinode's high resolution X-ray telescope, a team led by Jonathan Cirtain, a solar physicist at NASA's Marshall Space Flight Center, Huntsville, Ala., was able to peer low into the corona at the sun's poles and observe record numbers of X-ray jets. The jets are fountains of rapidly moving hot plasma. Previous research detected only a few jets daily.
With Hinode's higher sensitivity, Cirtain's team observed an average of 240 jets per day. They conclude that magnetic reconnection, a process where two oppositely charged magnetic fields collide and release energy, is frequently occurring in the low solar corona. This interaction forms both Alfvén waves and the burst of energized plasma in X-ray jets.
"These observations show a clear relationship between magnetic reconnection and Alfvén wave formation in the X-ray jets." said Cirtain. "The large number of jets, coupled with the high speeds of the outflowing plasma, lends further credence to the idea that X-ray jets are a driving force in the creation of the fast solar wind."
Another research team led by Bart De Pontieu, a solar physicist at Lockheed Martin's Solar and Astrophysics Laboratory, Palo Alto, Calif., focused on the sun's chromosphere, the region sandwiched between the solar surface and its corona. Using extremely high-resolution images from Hinode's Solar Optical Telescope, De Pontieu's team found that the chromosphere is riddled with Alfvén waves. When the waves leak into the corona, they are strong enough to power the solar wind.
"We find that most of these Alfvén waves have periods of several minutes, much longer than many theoretical models have assumed in the past," says De Pontieu. Comparisons with advanced computer simulations from the University of Oslo, Norway, indicate that reconnection is not the only source of the Alfvén waves. "The simulations imply that many of the waves occur when the sun's magnetic field is jostled around by convective motions and sound waves in the low atmosphere," continued De Pontieu.
Findings appear in the Dec. 7 issue of the journal Science.
Hinode was launched in September 2006 to study the sun's magnetic field and how its explosive energy propagates through the different layers of the solar atmosphere. It is a collaborative mission with NASA and the space agencies of Japan, the United Kingdom, Norway and Europe and Japan's National Astronomical Observatory. Marshall manages science operations and managed the development of the scientific instrumentation provided for the mission by NASA, industry and other federal agencies. The Lockheed Martin Advanced Technology Center, Palo Alto, Calif., is the lead U.S. investigator for the Solar Optical Telescope. The Smithsonian Astrophysical Observatory, Cambridge, Mass. is the lead U.S. investigator for the X-Ray Telescope.
Adapted from materials provided by NASA/Marshall Space Flight Center.

Fausto Intilla

www.oloscience.com

Stunning Image Of Nearby Spiral Galaxy

Source:

http://www.sciencedaily.com/releases/2007/11/071129092042.htm

ScienceDaily (Dec. 2, 2007) — Hubble has sent back an early Christmas card with this new NASA/ESA Hubble Space Telescope image of the nearby spiral galaxy Messier 74. It is an enchanting reminder of the impending season. Resembling glittering baubles on a holiday wreath, bright knots of glowing gas light up the spiral arms, with regions of new star birth shining in pink.

Messier 74, also called NGC 628, is a stunning example of a 'grand-design' spiral galaxy that is viewed by Earth observers nearly face-on. Its perfectly symmetrical spiral arms emanate from the central nucleus and are dotted with clusters of young blue stars.
In the new Hubble image we can also see a smattering of bright pink regions decorating the spiral arms. These are huge, relatively short-lived, clouds of hydrogen gas which glow due to the strong radiation from hot, young stars embedded within them; glowing pink regions of ionized hydrogen (hydrogen that has lost its electrons). These regions of star formation show an excess of light at ultraviolet wavelengths and astronomers call them HII regions.
Tracing along the spiral arms are winding dust lanes that begin very near the galaxy's nucleus and follow along the length of the spiral arms. These spiral arms are not actually static 'arms' like spokes on a wheel. They are in fact density waves and move around the galaxy's disc compressing gas -- just as sound waves compress the air on Earth -- creating a new generation of young blue stars.
Messier 74 is located roughly 32 million light-years away in the direction of the constellation Pisces, the Fish. It is the dominant member of a small group of about half a dozen galaxies, the Messier 74 galaxy group. In its entirety, it is estimated that Messier 74 is home to about 100 billion stars, making it slightly smaller than our Milky Way.
The spiral galaxy was first discovered by the French astronomer, Pierre Méchain, in 1780. Weeks later it was added to Charles Messier's famous catalogue of deep-sky objects. Of all the objects in Messier's catalogue, number 74 has the lowest surface brightness. It is so difficult for amateur astronomers to spot through a telescope that it has been given the nickname 'The Phantom Galaxy'.
This Hubble image of Messier 74 is a composite of Advanced Camera for Surveys' data taken in 2003 and 2005. The filters used to create the colour image isolate light from blue, visible, and infrared portions of the spectrum, as well as emission from ionized hydrogen.
A small segment of this image used data from the Canada France Hawaii Telescope/Gemini Observatory telescope to fill in a region which Hubble did not image.
Adapted from materials provided by ESA/Hubble Telescope.

Fausto Intilla

www.oloscience.com

Huge Cloud Of High Temperature Gas Found In Orion Nebula

Source:

http://www.sciencedaily.com/releases/2007/11/071130101202.htm

ScienceDaily (Dec. 2, 2007) — Right in time for the festive season, ESA's XMM-Newton X-ray observatory has discovered a huge cloud of high-temperature gas resting in a spectacular nearby star-forming region, shaped somewhat like the silhouette of Santa Claus.

An early present for astronomers, the cloud suggests that hot gas from many star-forming regions leaks into the interstellar medium.
The Orion nebula is the nearest dense star-forming region to Earth that contains stars much more massive than the Sun. XMM-Newton’s newly-discovered gas cloud is composed of winds blowing from these high-mass stars that are heated to millions of degrees as they slam into the surrounding gas.
“There is one star in particular that dominates the nebula,” says Manuel Güdel, Paul Scherrer Institut, Switzerland, who led the team that discovered the gas. The star in question is theta1 Orionis C, a giant star around 40 times mass of the Sun, with a surface temperature of 40,000°C. Güdel and his colleagues think that the violent collision between the wind from this star and the surrounding dense gas is largely responsible for the newly-discovered hot gas cloud.
The high-temperature gas fills a region of the nebula that appears to be a huge cavity in optical and infrared images. The new observations, taken with XMM-Newton’s European Photon Imaging Camera (EPIC) camera, suggest that astronomers are seeing only a particular portion of the gas. The X-rays from this portion escape absorption by patches of cold gas covering much of the front of the Orion nebula.
The surrounding pattern of absorbing clouds gives the detected gas its Santa Claus shape, with his prominent hat outlined by the northern gas bubble. In its entirety, the hot gas probably fills the whole nebula.
The team discovered it whilst conducting a survey of the young stars in the region. In the background of many of those images was a faint glow of X-rays. “The diffuse signal came up time and time again. Finally, we realized that it was something real,” says Güdel.
The presence of the hot gas in a fairly common nebula like Orion is surprising. Although theory has predicted such hot gas clouds, previous observations suggested that a large number of massive stars shedding winds, or supernova explosions are required. These are found in some regions of vigorous high-mass star formation, which are scattered only rarely throughout the galaxy. The new observations show that much smaller collections of high mass stars can produce hot gas as well.
There are many star-forming regions similar to the Orion nebula throughout the galaxy, so there should be a network of channels and bubbles being filled up by the hot gas leaking from these various regions. “This is another possible way to enrich the interstellar medium. You don’t have to wait for a sudden supernova to explode. You can do it with just one or two massive stars over millions of years,” says Güdel.
The team now plans to obtain new observations to determine how the gas flows out of the Orion nebula. In particular, they want to see whether it connects with a giant bubble created by supernova explosions from previous generations of massive stars.
The paper reporting the discovery of the Orion plasma cloud, entitled "A million-degree plasma pervading the extended Orion nebula" appears in Science Express, the online version of the journal Science on 29 November 2007. The paper was written by M. Güdel, K. Briggs T. Montmerle, M. Audard, L. Rebull and S. Skinner.
Adapted from materials provided by European Space Agency.

Fausto Intilla

www.oloscience.com