Galaxies Are Born Of Violence Between Dark Matter and Interstellar Gas

Source:

http://www.sciencedaily.com/releases/2007/11/071129183827.htm

ScienceDaily (Nov. 30, 2007) — Researchers using supercomputer simulations have exposed a very violent and critical relationship between interstellar gas and dark matter when galaxies are born -- one that has been largely ignored by the current model of how the universe evolved.

The findings, published in Science, solve a longstanding problem of the widely accepted model -- Cold Dark Matter cosmology -- which suggests there is much more dark matter in the central regions of galaxies than actual scientific observations suggest.
"This standard model has been hugely successful on the largest of scales--those above a few million light-years--but suffers from several persistent difficulties in predicting the internal properties of galaxies," says Sergey Mashchenko, research associate in the Department of Physics & Astronomy at McMaster University. "One of the most troublesome issues concerns the mysterious dark matter that dominates the mass of most galaxies."
Supercomputer cosmological simulations prove that indeed, this problem can be resolved. Researchers modeled the formation of a dwarf galaxy to illustrate the very violent processes galaxies suffer at their births, a process in which dense gas clouds in the galaxy form massive stars, which, at the ends of their lives, blow up as supernovae.
"These huge explosions push the interstellar gas clouds back and forth in the centre of the galaxy," says Mashchenko, the lead author of the study. "Our high-resolution model did extremely accurate simulations, showing that this 'sloshing' effect -- similar to water in a bathtub-- kicks most of the dark matter out of the centre of the galaxy."
Cosmologists have largely discounted the role interstellar gas has played in the formation of galaxies and this new research, says Mashchenko, will force scientists to think in new terms and could lead to a better understanding of dark matter.
The simulations reported in the research paper were carried out on the Shared Hierarchical Academic Research Computing Network (SHARCNET).
Adapted from materials provided by McMaster University.

Fausto Intilla

www.oloscience.com

Astronomers Find Stellar Cradle Where Planets Form

Source:

http://www.sciencedaily.com/releases/2007/11/071129141146.htm

ScienceDaily (Nov. 30, 2007) — Astronomers at the University of Illinois have found the first clear evidence for a cradle in space where planets and moons form. The cradle, revealed in photographs taken with NASA’s Spitzer Space Telescope, consists of a flattened envelope of gas and dust surrounding a young protostar.

“We are seeing this object in the early stages of stellar birth,” said U. of I. astronomy professor Leslie Looney, the lead author of a paper accepted for publication in Astrophysical Journal Letters. “Eventually, the protostar will form into a star much like our sun, and the disk will form into planets and moons.”
Located about 800 light-years away in the constellation Cepheus, the object is obscured by dust and therefore invisible to the eye. However, the Spitzer Space Telescope’s sensitive infrared camera can penetrate the dust, and reveal the structures within.
The brightest structure consists of an enormous, almost linear flow of shocked molecular hydrogen gas erupting from the protostar’s two magnetic poles. These bipolar jets are so long, light would take about 1 1/2 years to travel from one end to the other.
In star-formation theory, a cloud of gas and dust collapses to form a star and its planets. As the cloud collapses, it begins to rotate faster and faster, like a pirouetting ice skater pulling in her arms. The force of the growing magnetic field ejects some of the gas and dust along the magnetic axis, forming the bipolar jets seen in the photograph.
“If material was not shed in this fashion, the protostar’s spin would speed up so fast it would break apart,” Looney said.
The planet-forming region is perpendicular to, and roughly centered on the polar jets. There, seen in silhouette against a bright background of galactic infrared emission, is the flattened disk of a circumstellar envelope.
Theorized, but never before seen, the flattened disk is an expected outcome for cloud-collapse theories that include magnetic fields or rotation.
“Some theories had predicted that envelopes flatten as they collapse onto their stars and surrounding planet-forming disks,” Looney said, “but we hadn’t seen any strong evidence of this until now.”
With Looney, co-authors of the paper are former undergraduate student John Tobin (now at the University of Michigan) and graduate student Woojin Kwon.
The Spitzer Space Telescope is operated by the Jet Propulsion Laboratory at the California Institute of Technology. Funding was provided by NASA.
Adapted from materials provided by University of Illinois.

Fausto Intilla

www.oloscience.com

Astronomers Discover Youngest Solar Systems Ever

Source:

http://www.sciencedaily.com/releases/2007/11/071129113705.htm

ScienceDaily (Nov. 29, 2007) — Astronomers at the University of Michigan have found what are believed to be some of the youngest solar systems yet detected.

The systems are around the young stars UX Tau A and LkCa 15, located in the Taurus star formation region just 450 light years away. Using a telescope that measures levels of infrared radiation, the researchers noticed gaps in the protoplanetary disks of gas and dust surrounding these stars. They say those gaps are most likely caused by infant planets sweeping those areas clear of debris.
A paper on the findings by astronomy doctoral student Catherine Espaillat, professor Nuria Calvet, and their colleagues is published in Astrophysical Journal Letters.
"Previously, astronomers were seeing holes at the centers of protoplanetary disks and one of the theories was that the star could be photoevaporating that material," said Espaillat, first author of the paper.
Photoevaporation refers to the process of heating up the dust and gas in the surrounding cloud until it evaporates and dissipates.
"We found that in some stars, including these two, instead of a hole, there's a gap," Espaillat said. "It's more like a lane has been cleared within the disk. That is not consistent with photoevaporation. The existence of planets is the most probable theory that can explain this structure."
The researchers used NASA's Spitzer Space Telescope for this study. The infrared orbiting telescope observes energy at wavelengths invisible to optical telescopes. That allowed astronomers to study these "pre-main sequence stars" in a deeper way.
A main sequence star is an average adult star, like the sun, which burns by converting hydrogen into helium. Pre-main sequence stars like UX Tau A and LkCa 15 haven't yet established this conversion process. They derive energy from gravitational contraction. UX Tau A and LkCa 15 are both about 1 million years old.
"They're baby stars," Calvet said. The sun, for comparison, is a middle-aged star at 4.5 billion years old. Calvet said this research adds new insights to the study of solar systems.
"We are looking for our history," Calvet said. "We are looking for the history of solar systems, trying to understand how they form."
The paper, published December 1, is called "On the Diversity of the Taurus Transitional Disks: UX Tau A & LkCa 15."
Adapted from materials provided by University of Michigan.

Fausto Intilla

www.oloscience.com

Earth-like Lightning On Venus, European Space Probe Confirms

Source:

http://www.sciencedaily.com/releases/2007/11/071128155513.htm

ScienceDaily (Nov. 29, 2007) — Venus is a hellish place of high temperatures and crushing air pressure. The European Space Agency's Venus Express mission adds into this mix the first confirmation that the Venusian atmosphere generates its own lightning.

"In addition to all the pressure and heat, we can confirm there is lightning on Venus -- maybe even more activity than there is here on Earth," said Christopher Russell, a NASA-sponsored scientist on Venus Express from the University of California, Los Angeles, and lead author of one of the Nature papers*. "Not a very good place to vacation, that is for sure."
The discovery puts Venus in elite planetary company. Scientists currently know of only three other planetary bodies in the entire universe that generate lightning -- Earth, Jupiter and Saturn. Lightning on Venus -- as well as on any other planet -- is an important discovery because the electrical discharges drive the chemistry of an atmosphere by breaking molecules into fragments that can then join with other fragments in unexpected ways. The lightning on Venus is unique from that found on Earth, Jupiter and Saturn in that it is the only lightning known that is not associated with water clouds. Instead, on Venus, the lightning is associated with clouds of sulfuric acid.
Any future missions to the second rock from the sun may have to take into account the electrical activity in the Venusian atmosphere.
The confirming measurements of the electrical discharges were made with data obtained by the Venus Express magnetometer instrument provided by the Space Research Institute in Graz, Austria. The measurements were taken once a day for two minutes, during a period when the spacecraft was closest to Venus. A Venusian day is about 117 days long.
With its primary mission completed, Venus Express will now embark upon its extended mission to watch Earth’s nearest planetary neighbor for two more Venusian days. Among other things, it will look for the telltale infrared radiation from lava flows. In 2010, when a Japanese mission, Venus Climate Orbiter, also called Planet-C, arrives at Venus, scientists will be able to compare results from the two spacecraft.
More than 250 scientists and engineers across Europe are involved in the Venus Express mission, supported by their institutes and national space agencies. The mission also sees the contribution of scientists from Russia and Japan, as well as from NASA, which sponsors 15 American Venus Express scientists and provides support to the radio science investigation via its Deep Space Network antennas.
*The discovery is part of the Venus Express science findings that appear in a special section of the Nov. 29 issue of the journal Nature.
Related images and graphics are online at http://www.esa.int/venus .
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Fausto Intilla

www.oloscience.com

Organic 'Building Blocks' Of Life Discovered In Titan's Atmosphere

Source:

http://www.sciencedaily.com/releases/2007/11/071128151808.htm

ScienceDaily (Nov. 29, 2007) — Scientists analysing data gathered by the Cassini spacecraft have confirmed the presence of heavy negative ions in the upper regions of Titan's atmosphere. These particles may act as organic building blocks for even more complicated molecules and their discovery was completely unexpected because of the chemical composition of the atmosphere (which lacks oxygen and mainly consists of nitrogen and methane). The observation has now been verified on 16 different encounters.

Professor Andrew Coates, researcher at UCL's Mullard Space Science Laboratory and lead author of a new paper*, says: "Cassini's electron spectrometer has enabled us to detect negative ions which have 10,000 times the mass of hydrogen. Additional rings of carbon can build up on these ions, forming molecules called polycyclic aromatic hydrocarbons, which may act as a basis for the earliest forms of life.
"Their existence poses questions about the processes involved in atmospheric chemistry and aerosol formation and we now think it most likely that these negative ions form in the upper atmosphere before moving closer to the surface, where they probably form the mist which shrouds the planet and which has hidden its secrets from us in the past. It was this mist which stopped the Voyager mission from examining Titan more closely in 1980 and was one of the reasons that Cassini was launched."
The new paper builds on work published in Science (May 11) where the team found smaller tholins, up to 8,000 times the mass of hydrogen, forming away from the surface of Titan.
Dr Hunter Waite of the South West Research Institute in Texas and author of the earlier study, said: "Tholins are very large, complex, organic molecules thought to include chemical precursors to life. Understanding how they form could provide valuable insight into the origin of life in the solar system."
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL.
*These findings will be published in Geophysical Research Letters on November 28.
Adapted from materials provided by University College London.

Fausto Intilla

www.oloscience.com

Discovering Teenage Galaxies Billions Of Light Years Away

Source:

http://www.sciencedaily.com/releases/2007/11/071127171056.htm

ScienceDaily (Nov. 28, 2007) — Staring for the equivalent of every night for two weeks at the same little patch of sky with ESO's Very Large Telescope, an international team of astronomers has found the extremely faint light from teenage galaxies billions of light years away. These galaxies, which the research team believes are the building blocks of normal galaxies like our Milky Way, had eluded detection for three decades, despite intensive searches.
The team, led by Martin Haehnelt of the University of Cambridge, UK, Michael Rauch and George Becker of the Observatories of the Carnegie Institution, USA, and Andy Bunker of the Anglo-Australian Observatory, reports their results in the 1 March 2008 issue of the Astrophysical Journal.
"The farther we look back into space the farther we see back in time," explained Rauch." We were actually trying to measure a faint signal from intergalactic gas caused by the cosmic ultraviolet background radiation. But as often happens in science, we got a surprise and found something we weren't looking for--dozens of faint, discrete objects emitting radiation from neutral hydrogen in the so-called Lyman alpha line, a fundamental signature of protogalaxies."
A popular theory of galaxy formation predicts that the gas accreted forming smaller protogalaxies, which then collided and merged to become the massive galaxies seen today. The new discovery lends strong support to this theory.
During the 1990s there was mounting evidence in favor of this hierarchical picture of galactic evolution, including measurements of distant quasars by Rauch and collaborators that showed how the properties of cosmic gas clouds--the reservoir of matter for galaxy formation--fit within that scheme.
"Most of those gas clouds are dark and visible only as foreground objects, which cast something of a shadow against a bright background quasar," Becker said. "Intriguingly, one class of these shadows--known as damped Lyman alpha systems--was suspected to arise when those small, protogalactic building blocks intersect the line-of-sight to the quasar. For many years, these shadows were our only hint that a population of numerous early galaxies existed."
"This is the first time that the sky has been searched to this depth and the unrivalled sensitivity of the picture taken with the VLT was key to succeeding," says Haehnelt.
"Previous attempts have usually been frustrated by the difficulty of detecting extremely faint objects: the amount of time required even with an 8-metre class telescope like the VLT considerably exceeds typical observing time awards. We have thus exploited the periods of less good weather with the FORS2 spectrograph at the VLT, taking advantage of the service observing mode," says Becker.
In service mode, ESO staff astronomers at Paranal are responsible for carrying out the actual observations, taking all the specific requirements into account.
"We were actually trying to measure a faint signal from intergalactic gas caused by the cosmic ultraviolet background radiation. But as often happens in science, we got a surprise and found something we weren't looking for--dozens of faint, discrete objects emitting radiation from neutral hydrogen in the so-called Lyman alpha line, a fundamental signature of protogalaxies," explains Rauch.
The same small patch of sky, centred on a quasar, was observed between 2004 and 2006 for an unprecedented 92 hours, the equivalent of about 12 complete nights, allowing the astronomers to obtain a spectrum of the Universe when it was only 2 billion years old.
The result of this search is the detection of 27 faint objects. The weak light signal that the team has detected from these distant objects implies low star formation rates and a small amount of chemical enrichment, suggesting that they are indeed at an early stage of formation.
"The properties of the emitters seem to provide an excellent match to those of 'Damped Lyman Alpha Systems', the main reservoir of neutral hydrogen in the far Universe," says Andy Bunker. "This suggests that the objects found are the long-sought counterparts of the DLAS in emission. The new observations confirm theoretical research proposing that galaxies like our own have formed by the amalgamation of small proto-galaxies early on in the history of the Universe," he adds.
"What makes our discovery particularly exciting is that it opens the route to find large numbers of building blocks of normal galaxies and that we will now be able to study in detail how galaxies like our Milky Way have come together, " says Martin Haehnelt.
The results are reported in a paper in press in the Astrophysical Journal ("A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems", by M. Rauch et al.). The team is composed of Michael Rauch and George Becker (Observatories of the Carnegie Institution of Washington, Pasadena, USA), Martin Haehnelt (Institute of Astronomy, Cambridge, UK), Andrew Bunker (Anglo-Australian Observatory and School of Physics, Exeter, UK), Francine Marleau (Spitzer Science Center, Caltech, USA), James Graham (University of California, Berkeley, USA), Stefano Cristiani (Osservatorio Astronomico di Trieste, INAF, Italy), Matt J. Jarvis (University of Hertfordshire, UK), Cedric Lacey, Simon Morris, and Tom Theuns (Durham University, UK), Celine Peroux (Observatoire Astronomique de Marseille-Provence, France), and Huub Röttgering (Leiden Observatory, The Netherlands)
Adapted from materials provided by ESO.

Fausto Intilla
www.oloscience.com

Einstein's Biggest Blunder? Dark Energy May Be Consistent With Cosmological Constant

Source:

http://www.sciencedaily.com/releases/2007/11/071127142128.htm

ScienceDaily (Nov. 28, 2007) — Einstein's self-proclaimed "biggest blunder" -- his postulation of a cosmological constant (a force that opposes gravity and keeps the universe from collapsing) -- may not be such a blunder after all, according to the research of an international team of scientists that includes two Texas A&M University researchers.

The team is working on a project called ESSENCE that studies supernovae (exploding stars) to figure out if dark energy -- the accelerating force of the universe -- is consistent with Einstein's cosmological constant.
Texas A&M researchers Nicholas Suntzeff and Kevin Krisciunas are part of the project, which began in October of 2002 and is scheduled to end next month after achieving its goal of discovering and studying 200 supernovae. The team uses a 4-meter diameter telescope in Chile during the observing season of October to December to find the supernovae.
In 1917, Einstein was working on his Theory of General Relativity and was trying to come up with an equation that describes a static universe -- one that stands still and does not collapse under the force of gravity in a big crunch. In order to keep the universe static in his theory, Einstein introduced a cosmological constant -- a force that opposes the force of gravity.
Then, 12 years later, Edwin Hubble discovered that the universe is not static -- it is actually expanding. So Einstein scrapped his idea of a cosmological constant and dismissed it as his biggest blunder.
In 1998, however, two teams of scientists, one of which Texas A&M researcher Suntzeff co-founded, discovered that the universe is not only expanding, but its expansion is actually accelerating -- going faster and faster.
"So there had to be some other force that had overcome the force of gravity and is driving the universe into an exponential acceleration," Suntzeff said. This opposing force is what scientists now call dark energy, and it is believed to constitute roughly 74 percent of the universe. The other constituents of the universe are dark matter, which composes about 22 percent of the universe, and ordinary matter, which is about 4 percent.
"Eighty years later, it turns out that Einstein may have been right [about a cosmological constant]," Krisciunas said. "So he was smarter than he gave himself credit for."
The type of supernovae that the ESSENCE team studies all give off the same amount of energy and have essentially the same peak brightness. Researchers can compare the observed brightness of a supernova that they see in the sky to its known actual brightness to figure out how far away the supernova is.
Researchers also look at what is called the redshift of the supernova, which tells them how fast the universe is expanding. When scientists compare the distance of the supernova to its redshift, they can measure the acceleration of the expansion of the universe. This acceleration is caused by the force scientists call dark energy.
The ESSENCE team can then use the value of the acceleration to figure out the density of dark energy, which they then use to calculate what is called the w-parameter. For Einstein's cosmological constant to be correct, the w-parameter must equal -1, and so far, the results of the ESSENCE project seem to confirm that it is indeed very close to -1.
"The magic value is -1 exactly," Krisciunas said. "If the number turns out to be precisely -1, then this dark energy is a relatively simple thing -- it is Einstein's cosmological constant." The team won't have the final results until later next year, but right now, the measurement is coming in at -1 plus or minus 10 percent error, Suntzeff said, so the initial data seems to point to Einstein being correct.
"We can never test [dark energy] in the laboratory, so astronomers have to measure it [through observational data], and one of the ways we're measuring it is with supernovae in the ESSENCE project," Suntzeff said. "Dark energy is completely unexplained by conventional physics. Perhaps this is a manifestation of the 5th dimension from string theory. Or maybe it is a new vacuum energy density that is changing slowly in time. We have no idea, and that is what excites both physicists and astronomers."
Adapted from materials provided by Texas A&M University.

Fausto Intilla

www.oloscience.com

Voyager 2 Spacecraft Set to Reach Space Milestone

Source:

http://www.sciencedaily.com/releases/2007/11/071127171052.htm

ScienceDaily (Nov. 28, 2007) — Using a computer model simulation, Haruichi Washimi, a physicist at UC Riverside, has predicted when the interplanetary spacecraft Voyager 2 will cross the "termination shock," the spherical shell around the solar system that marks where the solar wind slows down to subsonic speed.

According to Washimi's simulations, the spacecraft is set to cross the termination shock in late 2007-early 2008. To make this forecast, Washimi and his colleagues used data from Voyager 2 and performed a global "magneto-hydrodynamic simulation" -- a method that allows for precise and quantitative predictions of geomagnetic disturbances caused by solar activities.
Because Voyager 2's crossing of the shock is expected to be an abrupt and relatively brief event, scientists are working to ensure that the most is made of the opportunity. With an idea of when the spacecraft will cross the shock, they are better able to maximize coverage of the crossing.
"Washimi's model has predicted the location of a boundary that is approximately 90 times farther from the sun than is the Earth, to within a few percent," said Gary Zank, the director of the Institute of Geophysics and Planetary Physics and one of the coauthors of the research paper. "This is truly remarkable given the enormous complexity of the physics involved, the temporal and spatial scales involved, and the variability of the solar wind conditions."
The solar wind -- a stream of charged particles ejected by the sun in all directions -- travels at supersonic speeds when it leaves the sun, until it eventually encounters the interstellar medium made up of plasma, neutral gas and dust.
At the termination shock, located at 7-8.5 billion miles from the sun, the solar wind is decelerated to less than the speed of sound. The boundary of the termination shock is not fixed, however, but wobbly, fluctuating in both time and distance from the sun, depending on solar activity.
"This is the first time the termination-shock position has been forecast in this way," said Washimi, the lead author of the research paper and a scientist at the Institute of Geophysics and Planetary Physics. "After it crosses this boundary, Voyager 2 will be in the outer heliosphere beyond which lies the interstellar medium and galactic space. Our simulations also show that the spacecraft will cross the termination shock again in the middle of 2008. This will happen because of the back and forth movement of the termination-shock boundary. This means Voyager 2 will experience multiple crossings of the termination shock. These crossings will come to an end after the spacecraft escapes into galactic space."
Voyager 2 was launched Aug. 20, 1977. It visited four planets and their moons in the course of its journey into space. Its sister spacecraft Voyager 1, which was launched Sept. 5, 1977, crossed the termination shock in December 2004 -- earlier than Voyager 2 because of a shorter trajectory. Both spacecraft are currently operational, but power sources have degraded and some of the instrumentation no longer works optimally. In the future, the spacecraft will encounter their next milestone in space: the heliopause, which is the boundary where the interstellar medium brings the solar wind to a halt.
Study results appear in the Dec. 1 issue of The Astrophysical Journal.
Washimi and Zank were joined in the research by UCR's Qiang Hu; Takashi Tanaka of Kyushu University, Japan; and Kazuoki Munakata of Shinshu University, Japan. The research was funded by grants from the National Science Foundation and the National Aeronautics and Space Administration.
Adapted from materials provided by University of California - Riverside.

Fausto Intilla

www.oloscience.com

Watching Galaxies Grow Old Gracefully

Source:

http://www.sciencedaily.com/releases/2007/11/071125181756.htm

ScienceDaily (Nov. 26, 2007) — n the early 1900s, Edwin Hubble made the startling discovery that our Milky Way galaxy is not alone. It is just one of many galaxies, or "island universes," as Hubble dubbed them, swimming in the sea of space.

Now, a century later, NASA's Galaxy Evolution Explorer is helping piece together the evolution of these cosmic species. Since its launch in 2003, the mission has surveyed tens of thousands of galaxies in ultraviolet light across nine billion years of time. The results provide new, comprehensive evidence for the "nurture" theory of galaxy evolution, which holds that the galaxies first described by Hubble – the elegant spirals and blob-like ellipticals -- are evolutionarily linked.
According to this "nurture" theory, a typical young galaxy begins life as a spiral that is actively churning out stars. Over time, the spiral might merge with another spiral or perhaps an irregular-shaped galaxy, before kicking out a few more bursts of newly minted stars. Eventually, the galaxy slows down its production of stars and settles into later life as an elliptical.
"Our data confirm that all galaxies begin life forming stars," said Chris Martin, the principal investigator for the Galaxy Evolution Explorer at the California Institute of Technology in Pasadena, Calif. "Then through a combination of mergers, fuel exhaustion and perhaps suppression by black holes, the galaxies eventually stop producing stars."
When astronomers talk about galaxies today, they tend to refer to them by their color, either blue or red, instead of by their shape. Most blue galaxies are smaller spirals or irregulars, and most red galaxies are larger ellipticals, though there are some exceptions.
Why color-code the galaxies? Their color indicates how actively they are making new stars. Younger stars shine in ultraviolet or blue light, so galaxies that appear blue are busily producing stars. Older stars emit infrared or red light, so galaxies that look red have shut down their star-making factories. Roughly half of all galaxies are blue and half are red.
Scientists have long postulated that blue galaxies grow up to become red. They proposed that something happens to the blue galaxies to cause them to run out of star-making material, or gas, and mature into the passive red ones. For this "nurture" theory to be true, there should be a population of "teenage" galaxies in the process of transitioning from blue to red, or young to old. But such a cosmic metamorphosis should take billions of years. How can astronomers, with a significantly shorter lifespan, study a process that takes that long?
One solution is to look at lots and lots of galaxies. Imagine a hypothetical alien trying to figure out how and if humans age from only a handful of snapshots showing people of different ages. The aliens might assume that little people grow into big ones, but they could better piece together the life of a typical human if they could look through boxes and boxes of photographs.
The Galaxy Evolution Explorer was designed to provide astronomers with just such a massive portfolio of galaxies. Its troves of data have allowed scientists to find a significant number of teenage galaxies – and thus proof that youthful spiral, or blue, galaxies will eventually grow up to become the elderly elliptical, or red, galaxies.
"The nurture theory of galaxy evolution predicted that there would be galaxies in transition," said Martin. "Finding these galaxies required ultraviolet light, because they really stand out at this wavelength. And because they are rare, we had to look at many. The Galaxy Evolution Explorer allowed us to do this."
Visible-light data from the Sloan Digital Sky Survey also helped to establish the age of the teenage galaxies and the rates at which they are running out of star-making fuel. These findings suggest that some of the young galaxies are ripening into old age quickly, while others are leisurely strolling into their golden years.
Evidence for the "nurture" theory of galaxy evolution can be found in a report in the Astrophysical Journal. Martin is the lead author.
Adapted from materials provided by National Aeronautics And Space Administration.

Fausto Intilla

www.oloscience.com

New Light On Early Formation Of Earth And Mars

Source:

http://www.sciencedaily.com/releases/2007/11/071121220939.htm

ScienceDaily (Nov. 25, 2007) — A team of scientists from NASA's Johnson Space Center (JSC) and the Lunar and Planetary Institute and the University of California, Davis (UCD) has found that terrestrial planets such as the Earth and Mars may have remained molten in their early histories for tens of millions of years. The findings indicate that the two planets cooled slower than scientists thought and a mechanism to keep the planet interiors warm is required.

These new data reveal that the early histories of the inner planets in the solar system are complex and involve processes no longer observed. Evidence of these processes has been preserved in Mars, while it has been erased in Earth. So Mars is probably the best opportunity to understand how Earth formed.
The formation of the solar system can be dated quite accurately to 4,567,000,000 years ago, said Qing-Zhu Yin, assistant professor of geology at UC Davis and an author on a new paper. Mars' metallic core formed a few million years after that. Previous estimates for how long the surface remained molten ranged from thousands of years to several hundred million years.
The persistence of a magma ocean on Mars for 100 million years is "surprisingly long," Yin said. It implies that at the time, Mars must have had a thick enough atmosphere to insulate the planet and slow down cooling, he said.
Scientists think that early crust formation alone cannot account for the slow cooling magma ocean seen in large planets. This new evidence instead implies that Mars, at one time, had a primitive atmosphere that acted as the insulator. “The primitive atmosphere was composed mostly of hydrogen left over from accretion into a rocky planet, but was removed, probably by impacts, about 100 million years after the planet formed,” said Debaille.
Debaille and her colleagues performed precise measurements of neodymium isotope compositions of nine rare Martian meteorites called shergottites using mass spectrometers at JSC and UCD. Shergottites, named after the first-identified meteorite specimen that fell at Shergotty, India, in 1865, are a group of related meteorites from Mars composed primarily of pyroxene and feldspar.
The scientists examined shergottites because their large range in chemical compositions is thought to be a fingerprint of the formation of their deep sources very early in the history of Mars.
“These rocks were lavas that were made by melting deep in Mars and then erupted on the surface," said Brandon. “They were delivered to Earth as meteorites following impacts on Mars that exhumed them and launched them into space." Mars meteorites are a treasure chest of information about that planet and have been the focus of extensive research by scientists.
The metallic element samarium has two radioactive isotopes that decay at a known rate to two daughter neodymium isotopes. By precisely measuring the quantities of neodymium isotopes, Debaille was able to use these two radiometric clocks to derive the times of formation of the different shergottite sources in the Martian interior.
“We expected to find that their sources all formed at the same time,” said Debaille. “But what we found instead was that the shergottite sources formed at two different times. The oldest formed at 35 million years after the solar system began to condense from ice and dust into large planets about 4,567 million years ago. The youngest formed about 110 million years after the solar system began to condense.”
Debaille and her colleagues found that the scenario that best fits the data is one where a global-scale magma ocean formed from melting in Mars during the final stages of accretion and then slowly solidified over this time period.
“The most recent physical models for magma oceans suggest they solidify on timescales of a few million years or less, so this result is surprising,” said Brandon. “Some type of insulating blanket, either as a rocky crust or a thick atmosphere, is needed as an insulator to have kept the Martian interior hot.”
Vinciane Debaille (LPI), Alan Brandon (JSC), Qing-zhu Yin and Ben Jacobsen (UCD) present these new findings in a paper published in the Nov. 22 issue of Nature.
Adapted from materials provided by NASA, Johnson Space Center.

Fausto Intilla

www.oloscience.com

Astronomers Observe Acidic Milky Way Galaxies

Source:

http://www.sciencedaily.com/releases/2007/11/071121215003.htm

ScienceDaily (Nov. 23, 2007) — SRON astronomer Floris van der Tak is the first to have observed acidic particulate clouds outside of our own Milky Way galaxy. He did this by focusing the James Clerk Maxwell Telescope, located on Hawaii, on two nearby Milky Way galaxies. Astronomers think that acidification inhibits the formation of stars and planets in the dust clouds. Now it is a case of waiting for precise measurements from the SRON-built HIFI space instrument that will be launched on the Herschel space telescope next year.

The formation of stars and planets in the universe is a delicate process. Clouds of gas and matter rotate and draw together under the influence of gravity. Pressure and temperature then rise, which eventually leads to the kindling of a new star with planets potentially orbiting it. Yet why does this happen at some locations in the universe and not at others? What are the conditions for star and planet formation? How does this process start and when does it stop? Astronomers are fumbling in the dark.
‘The quantity of charged molecules in the dust cloud appears to have an inhibitory effect’, says Floris van der Tak. ‘These ensure that the magnetic fields can exert a greater influence on the cloud, as a result of which the entire cloud becomes agitated and the star-forming process is disrupted’. Observing these charged molecules directly is difficult. The ratio of acidic water molecules to ordinary water molecules is a measure of the quantity of charged molecules.
However, it is difficult to observe water molecules from under an atmosphere that is itself predominantly made up of water molecules. ‘It is like looking for stars in the daylight.’ On Earth it can only be done from a high mountain where the air is rarefied. Such a spot is the 4092 metre-high top of the Hawaiian volcano Mauna Kea, where the James Clerk Maxwell Telescope is located. Van der Tak focused this telescope on the Milky Way galaxies M82 en Arp 220, where he discovered areas rich in acidic water molecules.
‘Amazingly, what causes these acid water molecules to be present in both Milky Way galaxies is completely different’, says Van der Tak. ‘In Arp 220 they develop under the influence of X-rays in the vicinity of the central supermassive black hole. In M82, the cause is the ultraviolet radiation emitted by hot young stars in the star-forming area. Therefore, in these particular galaxies the process of star formation inhibits itself, due to more and more charged molecules being created.’
The astronomer will be able to deploy even heavier equipment for his research in the not too distant future. Next year, the European Space Agency (ESA) is launching the Herschel space telescope with the SRON-constructed Heterodyne Instrument for the Far Infrared (HIFI) attached to it. And in the 5000 metre-high and completely arid Atacama Desert in Chile, a start has been made on the construction of ALMA, 66 smart telescopes that can together produce detailed maps of the Milky Way galaxies. SRON is one of the partners involved in developing the detectors for these telescopes.
The results of the research of Floris van der Tak and his collegues Susanne Aalto of the Chamlers University of Technology, Onsala Sweden and Rowen Meijerink of the University of California are published in the scientific journal Astronomy & Astrophysics.
Adapted from materials provided by SRON Netherlands Institute for Space Research.

Fausto Intilla

www.oloscience.com

Astronomers Say Moons Like Ours Are Uncommon

Source:

http://www.sciencedaily.com/releases/2007/11/071121184530.htm

ScienceDaily (Nov. 22, 2007) — The next time you take a moonlit stroll, or admire a full, bright-white moon looming in the night sky, you might count yourself lucky. New observations from NASA's Spitzer Space Telescope suggest that moons like Earth’s – that formed out of tremendous collisions – are uncommon in the universe, arising at most in only five to 10 percent of planetary systems.

"When a moon forms from a violent collision, dust should be blasted everywhere," said Nadya Gorlova of the University of Florida, Gainesville, lead author of a new study appearing Nov. 20 in the Astrophysical Journal. "If there were lots of moons forming, we would have seen dust around lots of stars – but we didn't."
It's hard to imagine Earth without a moon. Our familiar white orb has long been the subject of art, myth and poetry. Wolves howl at it, and humans have left footprints in its soil. Life itself might have evolved from the ocean to land thanks to tides induced by the moon's gravity.
Scientists believe the moon arose about 30 million to 50 million years after our sun was born, and after our rocky planets had begun to take shape. A body as big as Mars is thought to have smacked into our infant Earth, breaking off a piece of its mantle. Some of the resulting debris fell into orbit around Earth, eventually coalescing into the moon we see today. The other moons in our solar system either formed simultaneously with their planet or were captured by their planet's gravity.
Gorlova and her colleagues looked for the dusty signs of similar smash-ups around 400 stars that are all about 30 million years old – roughly the age of our sun when Earth's moon formed. They found that only one out of the 400 stars is immersed in the telltale dust. Taking into consideration the amount of time the dust should stick around, and the age range at which moon-forming collisions can occur, the scientists then calculated the probability of a solar system making a moon like Earth's to be at most five to 10 percent.
"We don't know that the collision we witnessed around the one star is definitely going to produce a moon, so moon-forming events could be much less frequent than our calculation suggests," said George Rieke of the University of Arizona, Tucson, a co-author of the study.
In addition, the observations tell astronomers that the planet-building process itself winds down by 30 million years after a star is born. Like our moon, rocky planets are built up through messy collisions that spray dust all around. Current thinking holds that this process lasts from about ten million to 50 million years after a star forms. The fact that Gorlova and her team found only one star out of 400 with collision-generated dust indicates that the 30-million-year-old stars in the study have, for the most part, finished making their planets.
"Astronomers have observed young stars with dust swirling around them for more than 20 years now," said Gorlova. "But those stars are usually so young that their dust could be left over from the planet-formation process. The star we have found is older, at the same age our sun was when it had finished making planets and the Earth-moon system had just formed in a collision."
For moon lovers, the news isn't all bad. For one thing, moons can form in different ways. And, even though the majority of rocky planets in the universe might not have moons like Earth's, astronomers believe there are billions of rocky planets out there. Five to 10 percent of billions is still a lot of moons.
Other authors of the paper include: Zoltan Balog, James Muzerolle, Kate Y. L. Su and Erick T. Young of the University of Arizona, and Valentin D. Ivanov of the European Southern Observatory, Chile.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA.
Adapted from materials provided by University Of Arizona.

Fausto Intilla

www.oloscience.com

Astronomers Discover Stars With Carbon Atmospheres

Source:

http://www.sciencedaily.com/releases/2007/11/071121145005.htm

ScienceDaily (Nov. 21, 2007) — Astronomers have discovered white dwarf stars with pure carbon atmospheres. The discovery could offer a unique view into the hearts of dying stars.These stars possibly evolved in a sequence astronomers didn't know before. They may have evolved from stars that are not quite massive enough to explode as supernovae but are just on the borderline. All but the most massive two or three percent of stars eventually die as white dwarfs rather than explode as supernovae.
When a star burns helium, it leaves "ashes" of carbon and oxygen. When its nuclear fuel is exhausted, the star then dies as a white dwarf, which is an extremely dense object that packs the mass of our sun into an object about the size of Earth. Astronomers believe that most white dwarf stars have a core made of carbon and oxygen which is hidden from view by a surrounding atmosphere of hydrogen or helium.
They didn't expect stars with carbon atmospheres.
"We've found stars with no detectable traces of helium and hydrogen in their atmospheres," said University of Arizona Steward Observatory astronomer Patrick Dufour. "We might actually be observing directly a bare stellar core. We possibly have a window on what used to be the star's nuclear furnace and are seeing the ashes of the nuclear reaction that once took place."
Dufour, UA astronomy Professor James Liebert and their colleagues at the Université de Montréal and Paris Observatory published the results in the Nov. 22 issue of Nature.
The stars were discovered among 10,000 new white dwarf stars found in the Sloan Digital Sky Survey. The survey, known as the SDSS, found about four times as many white dwarf stars previously known.
Liebert identified a few dozens of the newfound white dwarfs as "DQ" white dwarfs in 2003. When observed in optical light, DQ stars appear to be mostly helium and carbon. Astronomers believe that convection in the helium zone dredges up carbon from the star's carbon-oxygen core.
Dufour developed a model to analyze the atmospheres of DQ stars as part of his doctoral research at the Université de Montréal. His model simulated cool DQ stars, stars at temperatures between 5,000 degrees and 12,000 degrees Kelvin. For reference, our sun's surface temperature is around 5,780 degrees Kelvin.
When Dufour joined Steward Observatory in January, he updated his code to analyze hotter stars, stars as hot as 24,000 degrees Kelvin.
"When I first started modeling the atmospheres of these hotter DQ stars, my first thought was that these are helium-rich stars with traces of carbon, just like the cooler ones," Dufour said. "But as I started analyzing the stars with the higher temperature model, I realized that even if I increased the carbon abundance, the model still didn't agree with the SDSS data," Dufour said.
In May 2007, "out of pure desperation, I decided to try modeling a pure-carbon atmosphere. It worked," Dufour said. "I found that if I calculated a pure carbon atmosphere model, it reproduces the spectra exactly as observed. No one had calculated a pure carbon atmosphere model before. No one believed that it existed. We were surprised and excited."
Dufour and his colleagues have identified eight carbon-dominated atmosphere white dwarf stars among about 200 DQ stars they've checked in the Sloan data so far.
The great mystery is why these carbon-atmosphere stars are found only between about 18,000 degrees and 23,000 degrees Kelvin. "These stars are too hot to be explained by the standard convective dredge-up scenario, so there must be another explanation," Dufour said.
Dufour and Liebert say they these stars might have evolved from a star like the unique, much hotter star called H1504+65 that Pennsylvania State University astronomer John A. Nousek, Liebert and others reported in 1986. If so, carbon-atmosphere stars represent a previously unknown sequence of stellar evolution.
H1504+65 is a very massive star at 200,000 degrees Kelvin.
Astronomers currently believe this star somehow violently expelled all its hydrogen and all but a very small trace of its helium, leaving an essentially bare stellar nucleus with a surface of 50 percent carbon and 50 percent oxygen.
"We think that when a star like H1504+65 cools, it eventually becomes like the pure-carbon stars," Dufour said. As the massive star cools, gravity separates carbon, oxygen and trace helium. Above 25,000 degrees Kelvin, the trace helium rises to the top, forming a thin layer above the much more massive carbon envelope, effectively disguising the star as a helium-atmosphere white dwarf, Dufour and Liebert said.
But between 18,000 and 23,000 degrees Kelvin, convection in the carbon zone probably dilutes the thin helium layer. At these temperatures, oxygen, which is heavier than carbon, has probably sunk too deep to be dredged to the surface.
Dufour and his colleagues say that models of stars nine to 11 solar masses might explain their peculiar carbon stars.
Astronomers predicted in 1999 that stars nine or 10 times as massive as our sun would become white dwarfs with oxygen-magnesium-neon cores and mostly carbon-oxygen atmospheres. More massive stars explode as supernovae.
But scientists aren't sure where the dividing line is, whether stars eight, nine, 10 or 11 times as massive as our sun are required to create supernovae.
"We don't know if these carbon atmosphere stars are the result of nine-or-10 solar mass star evolution, which is a key question," Liebert said.
The UA astronomers plan making new observations of the carbon atmosphere stars at the 6.5-meter MMT Observatory on Mount Hopkins, Ariz., in December to better pinpoint their masses. The observations could help define the mass limit for stars dying as white dwarfs or dying as supernovae, Dufour said.
Adapted from materials provided by University of Arizona.

Fausto Intilla

www.oloscience.com

Massive Project Will Scour Universe For Gravity Waves

Source:

http://www.sciencedaily.com/releases/2007/11/071116094829.htm

ScienceDaily (Nov. 18, 2007) — Astronomers are searching for gravitational waves in space, a feat that would literally change what we know about the cosmos. Using new tools to look at the universe, says Patrick Brady, often has led to discoveries that change the course of science. History is full of examples.

"Galileo was the first person to use the telescope to view the cosmos," says Brady, a UWM professor of physics. "His observations with the new technology led to the discovery of moons orbiting Jupiter and lent support to the heliocentric model of the solar system."
Just such an opportunity exists today with a unique observatory that is scanning the skies, searching for one of Einstein's greatest predictions -- gravitational waves.
Gravitational waves are produced when massive objects in space move violently. The waves carry the imprint of the events that cause them. Scientists already have indirect evidence that gravitational waves exist, but have not directly detected them.
UWM researchers, backed by considerable funding from the National Science Foundation, are taking a leadership role in the quest.
It is an epic undertaking involving about 500 scientists worldwide, including Brady and other members of UWM's Center for Cosmology and Gravitation: associate professors Alan Wiseman and Jolien Creighton, and assistant professor Xavier Siemens.
Two UWM adjunct physicists, who work at the Max Planck Institute in Germany, also are involved -- former UWM professor Bruce Allen and scientist Maria Alessandra Papa.
"It's an unimaginable opportunity to be on the forefront of scientific discovery," says Creighton.
The Laser Interferometer Gravitational-wave Observatory, or LIGO, consists of detectors at two U.S. sites managed by the California Institute of Technology (Caltech) and Massachusetts Institute of Technology (MIT).
UWM's physicists are analyzing the data generated by the LIGO facilities.
The project is supported with a sizable investment of grant money from both federal and UWM sources.
Last year, UWM's LIGO group brought in $3 million in grant funding. Since 1999, UWM has received more than $9 million for the project, with much of it going toward a supercomputer called Nemo that operates unobtrusively on the second floor of the Physics Building.
Stretching and squeezing
The LIGO observatories use lasers to accurately monitor the distance between a central station and mirrors suspended three miles away along perpendicular arms. When a gravitational wave, a traveling ripple in space-time, passes by, the mirror in one arm will move closer to the central station, while the other mirror will move away.
The change in distance caused by stretching and squeezing is what LIGO is designed to measure, says Wiseman.
Those changes will be inconceivably tiny. LIGO can record distortions at a scale so small, it is comparable in distance to a thousandth of the size of an atomic nucleus.
LIGO records a series of numbers -- lots of them -- and feeds them to several supercomputer clusters around the country, including UWM's Nemo cluster.
Think of a modern hard disk on a desktop computer, which stores about 100 gigabytes. LIGO fills up about 10 of those at Nemo in a single day, says Brady.
The computer's job is to sort out the numerical patterns representing gravitational waves buried in ambient noise produced by lots of other vibrations -- from internal vibrations of the equipment itself, to magnetic fluctuations from lightning storms, to seismic vibrations from trains rolling along the tracks a few miles from the observatory, or from earthquakes on the other side of the world.
"There are thousands or even millions of different signals that could be emitted from space," says Wiseman. "So you have to take each segment of data individually. That turns out to be a formidable computational problem."
Nemo performs many billions of calculations per second in its search for these signals.
Space sounds
The strings of numbers from LIGO are like tracks on a compact disk, says Brady. That means, once detected, gravitational-wave signals can be converted into sound.
In fact, scientists have already simulated, based on mathematical predictions, what certain events in space will sound like.
When two black holes are merging, for example, you might expect to hear a "chirp" that represents the spiraling together of the black holes just before they collide. "The spiral can go on for tens of thousands of years," says Brady. "The sound is the identifying signal of the last few seconds of the process!"
Those analyzing the data from space could actually listen to the data. Instead, scientists look for the signals using computers like Nemo.
To augment the computing capacity, UWM is hosting a way for anyone with a computer and a high-speed Internet connection to join the astrophysical treasure hunt. Called "Einstein@Home, the program borrows computer power available when participants are not using it, and pool those resources to aid in filtering the massive amounts of data from LIGO.
Possible secrets
Scientists concede that the current LIGO facilities will need to be improved to increase the chances of detecting gravitational waves. More NSF funding to do that is requested in the 2009 U.S. budget currently winding its way through the approval process.
For now, the best hope is to detect events relatively close to Earth.
So what is the likelihood of success?
"The events we are looking for may only happen once every million years in our galaxy," says Wiseman, "but if your instrument is sensitive enough to see such events in, say, one million galaxies, then the probability of detecting something is much larger."
Gravitational waves may hold secrets to the nature of black holes, the unknown properties of nuclear material, and maybe even how the universe began.
"We've only been able to find out about the universe since it became cool," says Siemens. "But with gravitational waves, we'll see the universe when it was much younger -- and hotter."
But then again, scientists don't really know.
"I think we're in for a surprise," says Siemens. "We have all these ideas about what we think we will find, but it could be something completely different."
Adapted from materials provided by University of Wisconsin - Milwaukee.

Fausto Intilla

www.oloscience.com

How To Make The Brightest Supernova Ever: Explode, Collapse, Repeat

Source:

http://www.sciencedaily.com/releases/2007/11/071114151527.htm

ScienceDaily (Nov. 15, 2007) — A supernova observed last year was so bright--about 100 times as luminous as a typical supernova--that it challenged the theoretical understanding of what causes supernovae. But Stan Woosley, professor of astronomy and astrophysics at the University of California, Santa Cruz, had an idea that he thought could account for it--an extremely massive star that undergoes repeated explosions. When Woosley and two colleages worked out the detailed calculations for their model, the results matched the observations of the supernova known as SN 2006gy, the brightest ever recorded.

The researchers describe the model in a paper to be published in the November 15 issue of the journal Nature. Woosley's coauthors are Sergei Blinnikov, a visiting researcher at UCSC from the Institute of Theoretical and Experimental Physics in Moscow, and Alexander Heger of Los Alamos National Laboratory.
"This was a stupendously bright supernova, and we think we have the leading model to explain it. It's a new mechanism for making a supernova, and for doing it again and again in the same star," Woosley said. "We usually think of a supernova as the death of a star, but in this case the same star can blow up half a dozen times."
The first explosion throws off the star's outer shell and produces a not-very-bright supernova-like display. The second explosion puts another supernova's worth of energy into a second shell, which expands at high velocity until it collides with the first shell, producing an extraordinarily brilliant display.
"The two shells collide out at a distance such that the full kinetic energy is converted into light, so it is up to 100 times more luminous than an ordinary supernova," Woosley said. "Usually a supernova only converts 1 percent of its kinetic energy into light, because it has to expand so much before the light can escape."
This mechanism requires an extremely massive star, 90 to 130 times the mass of the Sun, he said. As a star this big nears the end of its life, the temperature in the core gets so hot that some of the energy from gamma-ray radiation converts into pairs of electrons and their anti-matter counterparts, positrons. The result is a phenomenon called "pair instability," in which conversion of radiation into electron-positron pairs causes the radiation pressure to drop, and the star begins to contract rapidly.
"As the core contracts it goes deeper into instability until it collapses and begins to burn fuel explosively. The star then expands violently, but not enough to disrupt the whole star," Woosley said. "For stars between 90 and 130 solar masses, you get pulses. It hits this instability, violently expands, then radiates and contracts until it gets hotter and hits the instability again. It keeps going until it loses enough mass to be stable again."
Stars in this size range are very rare, especially in our own galaxy. But they may have been more common in the early universe. "Until recently, we would have said such stars don't exist. But any mechanism that could explain this event requires a very large mass," Woosley said.
Other researchers had suggested pair instability as a possible mechanism for some supernovae, but the idea of repeated explosions--called "pulsational pair instability"--is new. According to Woosley, the new mechanism can yield a wide variety of explosions.
"You could have anywhere from two to six explosions, and they could be weak or strong," he said. "A lot of variety is possible, and it gets even more complicated because what's left behind at the end is still about 40 solar masses, and it continues to evolve and eventually makes an iron core and collapses, so you can end up with a gamma-ray burst. The possibilities are very exciting."
Adapted from materials provided by University of California - Santa Cruz.

Fausto Intilla

www.oloscience.com

Nearby Barred Spiral Galaxy Shows Off Its Warped Disc

Source:

http://www.sciencedaily.com/releases/2007/11/071109104738.htm

ScienceDaily (Nov. 12, 2007) — Known until now as a simple number in a catalogue, NGC 134, the 'Island in the Universe' is replete with remarkable attributes, and the VLT has clapped its eyes on them. Just like our own Galaxy, NGC 134 is a barred spiral with its spiral arms loosely wrapped around a bright, bar-shaped central region.

One feature that stands out is its warped disc. While a galaxy's disc is often pictured as a flat structure of gas and stars surrounding the galaxy's centre, a warped disc is a structure that, when viewed sideways, resembles a bent record album left out too long in the burning Sun.
Warps are actually not atypical. More than half of the spiral galaxies do show warps one way or another, and our own Milky Way also has a small warp.
Many theories exist to explain warps. One possibility is that warps are the aftermath of interactions or collisions between galaxies. These can also produce tails of material being pulled out from the galaxy. The VLT image reveals that NGC 134 also appears to have a tail of gas stripped from the top edge of the disc.
So did NGC 134 have a striking encounter with another galaxy in the past? Or is some other galaxy out there exerting a gravitational pull on it? This is a riddle astronomers need to solve.
The superb VLT image also shows that the galaxy has its fair share of ionised hydrogen regions (HII regions) lounging along its spiral arms. Seen in the image as red features, these are glowing clouds of hot gas in which stars are forming. The galaxy also shows prominent dark lanes of dust across the disc, obscuring part of the galaxy's starlight.
Studying galaxies like NGC 134 is an excellent way to learn more about our own Galaxy.
NGC 134 was discovered by Sir John Herschel at the Cape of Good Hope and is located in the Sculptor southern constellation. The galaxy is located about 60 million light-years away - when the light that was captured by the VLT originally left the galaxy, a dramatic episode of mass extinction had led to the disappearance of dinosaurs on Earth, paving the way for the appearance of mammals and later specifically of humans, who have built unique high-tech installations in the Atacama desert to satisfy their curiosity about the workings of the Universe. Still, NGC 134 is not very far away, by cosmological standards. It is the dominant member of a small group of galaxies that belongs to the Virgo or Local Supercluster and is one of the 200 brightest galaxies in our skies.
During his visit to ESO's Very Large Telescope at Paranal, the European Commissioner for Science and Research, Janez Potočnik, participated in an observing sequence and took images of this beautiful spiral galaxy.
Adapted from materials provided by ESO.

Fausto Intilla

www.oloscience.com

Mars Express Probes The Red Planet's Most Unusual Deposits

Source:

http://www.sciencedaily.com/releases/2007/11/071102094412.htm

ScienceDaily (Nov. 8, 2007) — The radar system on ESA’s Mars Express has uncovered new details about some of the most mysterious deposits on Mars: The Medusae Fossae Formation. It has given the first direct measurement of the depth and electrical properties of these materials, providing new clues about their origin.

The Medusae Fossae Formation (MFF) are unique deposits on Mars. They are also an enigma. Found near the equator, along the divide between the highlands and lowlands, they may represent some of the youngest deposits on the surface of the planet. This is inferred from the marked lack of impact craters dotting this terrain, unlike on older terrain.
Mars Express has been collecting data from this region using its Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS). Between March 2006 and April 2007, Mars Express orbited the region many times, taking radar soundings as it went.
For the first time, these radar soundings revealed the depth of the MFF layers, because of the time it took for the radar beam to pass through the top layers and bounce off the solid rock beneath. “We didn’t know just how thick the MFF deposits really were” says Thomas Watters, lead author of the results at the Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, USA.
“Some investigators thought they might be a thin veneer overlaying topographic rises in the lowlands. The new data show that the MFF are massive deposits over 2.5 km thick in some places where MARSIS orbits pass over them,” Watters added.
The MFF deposits intrigue scientists because they are associated with regions that absorb certain wavelengths of Earth-based radar. This had led to them being called ‘stealth’ regions because they give no radar echo. The affected wavelengths are 3.5 to 12.6 centimetres. MARSIS, however, works at wavelengths of 50 to over 100 metres. At these wavelengths, the radar waves mostly pass through the MFF deposits creating subsurface echoes when the radar signal reflects off the plains material beneath.
A variety of scenarios have been proposed for the origin and composition of these deposits. Firstly, they could be volcanic ash deposits from now-buried vents or other nearby volcanoes. Second, they could be deposits of wind-blown materials eroded from other martian rocks. Thirdly, they could be ice-rich deposits, somewhat similar to the layered ice deposits at the poles of the planet, but formed when the spin axis of Mars tilts over, making the equatorial region colder.
Deciding between these scenarios is not easy, even with the new data. The MARSIS data reveal the electrical properties of the layers. These suggest that the layers could be poorly packed, fluffy or dusty material. However it is difficult to understand how porous material from wind-blown dust can be kilometres thick and yet not be compacted under the weight of the overlying material.
On the other hand, although the electrical properties are consistent with water ice layers, there is no other strong evidence for the presence of ice today in the equatorial regions of Mars. “If there is water ice at the equator of Mars, it must be buried at least several metres below the surface,” says Jeffrey Plaut, MARSIS Co-Principal Investigator at the Jet Propulsion Laboratory, USA. This is because the water vapour pressure on Mars is so low that any ice near the surface would quickly evaporate.
So, the mystery of Mars’s Medusae Fossae Formation continues. “It is still early in the game. We may get cleverer with our analysis and interpretation or we may only know when we go there with a drill and see for ourselves,” says Plaut.
Giovanni Picardi at the University of Rome, La Sapienza, Principal Investigator of the experiment, says, “’Not only is MARSIS providing excellent scientific results but the team is also working on the processing techniques that will allow for more accurate evaluation of the characteristics of the subsurface layers and their constituent material. Hence, the possible extension of the mission will be very important to increase the number of observations over the regions of interest and improve the accuracy of the evaluations.
The results appear in ‘Radar sounding of the Medusae Fossae Formation Mars: Equatorial ice or dry, low-density deposits?’ published in today's issue of Science. The article is by T. R. Watters, B. Campbell, L. Carter, C. J. Leuschen, J. J. Plaut, G. Picardi, R. Orosei, A. Safaeinili, S. M. Clifford, W. M. Farrell, A. B. Ivanov, R. J. Phillips, E. R. Stofan and the MARSIS Science Team.
Adapted from materials provided by European Space Agency.

Fausto Intilla

www.oloscience.com

Space Mission Xeus Probes Origins Of The Universe

Source:

http://www.sciencedaily.com/releases/2007/11/071105162405.htm

ScienceDaily (Nov. 6, 2007) — A new mission seeks to study the origins of the universe. Professor Martin Turner of the Department of Physics and Astronomy is Co-Principal Investigator on XEUS - a next-generation X-ray space observatory.

XEUS, which stands for X-ray Evolving Universe Spectroscopy, aims to study the fundamental laws of the Universe. With unprecedented sensitivity to the hot, million-degree universe, XEUS will explore key areas of contemporary astrophysics: growth of supermassive black holes, cosmic feedback and galaxy evolution, evolution of large-scale structures, extreme gravity and matter under extreme conditions, the dynamical evolution of cosmic plasmas and cosmic chemistry.
Professor Turner is also Chair of the XEUS International Steering committee. He said: “XEUS is an X-ray observatory 30-50 times more sensitive than XMM-Newton, which will be placed 1.5 million km from Earth, beyond the Moon, at the second Lagrangian point, a quiet stable location where the instruments can observe the universe undisturbed.
“Because it is so large, the observatory has two spacecraft. The five-metre diameter X-ray lens is in one, and the instruments in another. The two spacecraft fly together, 35 metres apart, to keep the instruments at the focus of the lens.
“XEUS has been selected for study by ESA as part of its Cosmic Vision programme. If the study outcome is successful it will be launched on Ariane 5 from Kourou in 2018.
"We have been developing the XEUS concept for an advanced X-ray observatory, for many years. This acceptance by ESA is a major step forward for X-ray astronomers all over the world."
"The million degree universe, where gravity is the main source of energy, is the finest physics laboratory we have. XEUS will help us find out about the behaviour of matter under extreme conditions of temperature, pressure, and gravity. It will also let us study the influence of black holes on the formation of galaxies and stars; and ultimately planets and ourselves."
Dr Richard Willingale, of the University of Leicester and chairman of the XEUS telescope working group said.
“XEUS will use new lightweight silicon optics to make the lens, the same material used to make silicon chips; one of the instruments has sensors cooled to within a tiny fraction of absolute zero to study the chemistry and physics of matter surrounding black holes.”
Various international Space Agencies have expressed interest in cooperation in XEUS and discussions will start by the end of the year to ensure the earliest involvement in study work.
All the candidate missions are now competing in an assessment cycle which ends in 2011. Before the end of the cycle, there will be an important selection foreseen in 2009. At the end of this process, two missions will be proposed for implementation to ESA's Science Programme Committee, with launches planned for 2017 and 2018 respectively.
The selected missions fit well within the themes of ESA's Cosmic Vision 2015-2025 plan. The themes range from the conditions for life and planetary formation, to the origin and formation of the Solar System, the fundamental laws of our cosmos and the origin, structure and evolution of the Universe.
“The maturity of most of the proposals received demonstrates the excellence of the scientific community in Europe. This made the task of the SSAC very difficult but we believe that the set of selected missions will shape the future of European space science,” said Tilman Spohn, chairperson of the SSAC (German Aerospace Center, Berlin). “The next decade will indeed be very exciting for the scientific exploration of space.”
According to the chair of the Astronomy Working Group (AWG), Tommaso Maccacaro, (INAF – Osservatorio Astronomico di Brera) “The chosen candidates for astronomy missions show very promising and broad scientific return and have received excellent recommendations also from external referees.”
“Technical feasibility and potential for successful cooperation with other agencies are two factors which are clearly evident in the Solar System missions that have been chosen,” added Nick Thomas at the Physikalisches Institut, Universität Bern, chair of the Solar System Working Group.
In 2004, Professor Turner was honoured with a CBE for services to X-ray astronomy. Paying tribute to his colleague, Professor George Fraser, Director of the Space Research Centre, said at the time: “The award of a CBE to Martin Turner is very well-deserved recognition of a tremendous contribution to the field of X-ray Astronomy in a career of over thirty years here at Leicester. Martin has, perhaps uniquely, led the development of three major instruments in the field -launched on the EXOSAT (1983), Ginga (1987) and XMM-Newton (1999) –of which he is Principal Investigator- satellites. The last of these - the EPIC camera -has now performed flawlessly in orbit for four years. Martin, nothing daunted, is also heavily involved in the initial design stages of the successor to XMM, a giant European observatory called XEUS.”
Adapted from materials provided by University of Leicester.

Fausto Intilla

www.oloscience.com

Three New Exo-planets Discovered

Source:

http://www.sciencedaily.com/releases/2007/11/071105150909.htm

ScienceDaily (Nov. 5, 2007) — The UK's leading team of planet-hunting astronomers, the Wide Angle Search for Planets (WASP), have announced the discovery of three new planets.

These extra-solar planets were seen to pass in front of, or transit, their host star. Studying such planets outside of our Solar System allows scientists to investigate how planetary systems form. WASP is the first team to detect planets in both the Northern and Southern Hemisphere using this technique.
Exoplanet expert Dr. Pierre Maxted comments “The planets are known as ‘hot-Jupiters’ as they are similar to Jupiter but are so close to their parent star that they orbit it in less than two days. This means that these planets have a surface temperature of nearly 2000°C and so are unlikely to host life. But finding these planets is important as these stars could also host much smaller planets similar to Earth, although detecting these worlds will be much more difficult”.
The planets orbit around stars similar to our Sun that are located at a distance of 850 light-years away from the Earth. Two are in the constellation of Phoenix visible only from the Southern hemisphere, while the third is in the Northern constellation of Lyra. All three stars are too faint to be seen with the naked eye, but are easily detectable with a small telescope.
Dr Coel Hellier, of Keele University, comments "When we see a transit we can deduce the size and mass of the planet and also what it is made of, so we can use these planets to study how solar systems form."
WASP-4 and WASP-5 are the first planets discovered by the WASP project's cameras in South Africa, and were confirmed by a collaboration with Swiss and French astronomers. "These two are now the brightest transiting planets in the Southern hemisphere" said Dr Hellier. WASP-3 is the third planet that the team has found in the North, using the SuperWASP camera sited in the Canary Islands.
Using data produced by SuperWASP’s cameras, which monitor up to 400,000 stars every minute, the new extra-solar planets were discovered as they were seen to pass in front of their host star.
Explaining the discovery, Dr Don Pollacco of Queen’s University, Belfast, Astrophysics Research Centre said: “We take pictures of the sky and measure the brightness of stars. If a planet is going around one of these stars and it happens to pass across the face of that star, our cameras will pick up the light from the star getting a little fainter.
“Discoveries such as these open up a whole new area of astronomy. Such transiting planets are important because they are the only ones that can have their mass and size measured directly. Astronomers can determine what they are made of and armed with this information we can begin to understand how these solar systems were formed.”
The WASP project is the most ambitious project in the world designed to discover large planets. Funding for the project comes from the UK Universities and the Science and Technology Facilities Council.
Adapted from materials provided by Keele University.

Fausto Intilla

www.oloscience.com

Astronomers Discover Record Fifth Planet Around Nearby Star 55 Cancri

Source:

http://www.sciencedaily.com/releases/2007/11/071106133058.htm

ScienceDaily (Nov. 6, 2007) — Astronomers have discovered a record-breaking fifth planet around the nearby star 55 Cancri, making it the only star aside from the sun known to have five planets.

The discovery comes after 19 years of observations of 55 Cancri and represents a milestone for the California and Carnegie Planet Search team, which this year celebrates the 20th anniversary of its first attempts to find extrasolar planets by analyzing the wobbles they cause in their host star.
The team's long history of measurements - more than 300 for 55 Cancri alone - made the discovery of a five-planet system possible, said UC Berkeley astronomy professor Geoffrey Marcy, who with Paul Butler, now at the Carnegie Institution of Washington, began observations of many nearby stars at the University of California Lick Observatory in 1987.
The unique 55 Cancri system, located 41 light-years away in the direction of the constellation Cancer, is notable also because its clutch of four inner planets and one giant outer planet resembles our own solar system, though without an Earth or Mars.
"This system is interesting because there's a giant planet at 6 AU and four smaller planets inward of 0.8 AU, with a huge remaining gap in between, right where we would expect to find an Earth-sized planet," Marcy said.
An AU, or astronomical unit, is the average distance between the Earth and the sun, about 93 million miles.
According to lead author Debra Fischer, assistant professor of astronomy at San Francisco State University, the fifth planet is within the star's habitable zone in which water could exist as a liquid. Though the planet is a giant ball of gas, liquid water could exist on the surface of a moon or on other, rocky planets that may yet be found within the zone. "Right now, we are looking at a gap between the 260-day orbit of the new planet and the 14-year orbit of another gas giant, and if you had to bet, you'd bet that there is more orbiting stuff there."
Fischer noted that what occupies this gap has to be another planet around the size of Neptune or smaller, because anything larger would have destabilized the orbits of the other planets. All of the planets around 55 Cancri are in stable, nearly circular obits, like the eight planets in our solar system. Jupiter is located at 5.2 AU from the sun, while Mercury and Venus are closer than 0.72 AU. Earth and Mars are in the gap at 1 AU and 1.5 AU.
"We haven't found a twin of our solar system, because the four planets close to the star are all the size of Neptune or bigger," Marcy said, but he added that he's optimistic that continued observations will reveal a rocky planet within five years.
The new discovery, using data from the Lick Observatory and the W. M. Keck Observatory in Hawaii, has been accepted for publication in the Astrophysical Journal. The authors are Fischer, Marcy and their colleagues at the Carnegie Institution, San Francisco State University, UC Santa Cruz, Tennessee State University and UC Berkeley.
Fischer and Marcy also discussed their findings today during a media teleconference hosted by NASA.
"This work marks an exciting next step in the search for worlds like our own," said Michael Briley, an astronomer at the National Science Foundation. "To go from the first detections of planets around sun-like stars to finding a full-fledged solar system with a planet in a habitable zone in just 12 years is an amazing accomplishment and a testament to the years of hard work put in by these investigators."
In 1996, when Marcy and Butler found a Jupiter-sized planet orbiting close to 55 Cancri and circling every 14.6 days, it was only the fourth known star with an exoplanet. The second planet discovered in 2002 around the star turned out to circle in a more distant orbit, like our own Jupiter does, although the planet was four times the weight of Jupiter. The third, also discovered in 2002, was smaller, about half the size of Saturn, and was orbiting near the star with an orbit of 44 days, slightly farther than the first planet. The fourth planet, found in 2004, was so close to the star as to be hellishly hot - a Neptune-sized planet (14 times Earth's mass) with a 2.8 day period discovered in collaboration with a team led by Barbara McArthur of the University of Texas.
Although astronomers have found nearly 250 exoplanets, only one other star, mu Ara in the southern sky, is known to have four planets.
The newly-found fifth planet around 55 Cancri is also large - around half the size of Saturn, or at least 45 times the mass of Earth - and orbiting at about 0.785 AU in 260.8 days. Because the star 55 Cancri is older and dimmer than our sun, the habitable zone - the region in which planetary temperatures can be favorable for liquid water - is closer to the star than is our sun's habitable zone, and includes the new planet.
Finding multiple planets around a star is difficult because each planet produces its own stellar wobble. Marcy compares detecting the wobble within wobbles that are caused by one of several planets to picking out a single musical note from many played simultaneously. While the ear can do that, it took Marcy more than 10 months to convince himself that a fifth wobble was buried in the data.
The Doppler technique used by the search team sees this wobble as a change in the speed with which a star moves toward or away from us. The search team can detect velocities as small as 1 meter per second, which is walking speed.
55 Cancri has produced "a rat's nest of radial velocity data," Fischer said. "We probably still don't have all the planets. We are pulling out one thread at a time, disentangling all these orbits, and it has taken a lot more data and time than we predicted. I think it's amazing what we have been able to do with the system."
Coauthors with Fischer, Marcy and Butler are Steven S. Vogt and Greg Laughlin of UC Santa Cruz; Jason T. Wright, John A. Johnson and Kathryn M. G. Peek of UC Berkeley; Gregory W. Henry of Tennessee State University's Center of Excellence in Information Systems; and David Abouav, Chris McCarthy and Howard Isaacson of San Francisco State University.
The work was supported by the University of California, NASA and the National Science Foundation.
Adapted from materials provided by University of California - Berkeley.

Fausto Intilla

www.oloscience.com