Chemical Composition of Red Giant Star With More Carbon Than Oxygen in Its Atmosphere.

The attached figure represents the temporary hydrodynamic development (projection in the X-Y plan) of the binary system made up of a helium white dwarf and the core of a red giant, from the zero instant until their complete fusion, in a time of about 6,400 seconds. Every box has an estimated size of about the radius of the Sun. The colours are proportional to the logarithm of density (black is less dense, white is denser). (Credit: Image courtesy of University of Granada)

Source: ScienceDaily

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ScienceDaily (Jan. 14, 2010) — What are the peculiar type-R stars made? Where does the carbon present in their shell come from? These are the questions to be solved by a research work conducted by scientists of the department of Theoretical and Cosmos Physics of the University of Granada (Spain), where they have analysed the chemical composition and the evolutionary state of spectral type R carbon stars to try to explain the origin of the carbon enrichment present in its atmosphere.

Up to now, there had hardly been performed chemical analysis for this type of start. Type-R stars are peculiar red giant stars, as they show a higher presence of carbon than oxygen in their atmosphere (the usual composition in the Universe is exactly the opposite). They can be classified in hot-R starts and cold-R stars, depending on their effective temperature.
In the case of R-cold stars, this is the first chemical analysis of these characteristics carried out worldwide, whereas for R-hot stars, the existing chemical analyses were very old (more than 25 years) and with a lower spectral resolution than that of the UGR study.
The research has been conducted by Olga Zamora Sánchez and supervised by professors Carlos Abia and Inmaculada Domínguez. The scientists of the University of Granada have also studied the essential observational features of type-R stars (distribution in the Milky Way, kinematics, luminosity, etc.) .

A 23-star sample:
This research work has determined the chemical composition of a 23 type-R star sample (both hot and cold), using spectrums in the optics with high-spectral resolution, in order to obtain information about the origin of this type of stars. To this end, the scientists performed observations with a 2.2-metre in diameter telescope placed in Calar Alto (Almeria), and carried out a chemical analysis of elements such as carbon, oxygen, nitrogen, lithium and other heavy metals, such as technetium, strontium, barium or lanthanum.
Thus, the scientists have concluded that R-cold stars are identical to type-N stars (or normal carbon stars) originated in the AGB phase, whereas R-hot stars are different. About 40% of the R-hot stars of the sample were erroneously classified up now, and therefore the portion of these stars with regard to red giant stars could be considerably reduced regarding previous estimations thanks to this work.

The most comprehensive analysis:
The analysis of the University of Granada is the most complete conducted worldwide up to now (from an observational and theoretical approach) about type-R spectral stars. Besides, the scientists have carried out a numeric simulation for the first time of the most favourable scene for the formation of a R-hot star: the fusion of a helium white dwarf with a red giant. In the end, this scene has turned out to be unviable, and therefore the explanation of the origin of R-hot stars keeps representing a challenge for present star and nucleosynthesis development models.
Although the UGR scientists warn that this type of study has not immediate applications, the information obtained could be very valuable in the future as carbon, as everybody knows, is very important for the possible development of life in the Universe. Therefore, they say, explaining the origin of this element in the stars will be useful to study the production of one of the basic ingredients of life that we know.
The results of this research work will be sent for its publication in the near future in the journal Astronomy & Astrophysics.

Story Source:
Adapted from materials provided by University of Granada.

HIFI Resumes Quest for Water in Universe.

In the daily communications with Herschel/HIFI strange readings had been received. HIFI was in a state that was not described in the manuals. (Credit: Image courtesy of SRON Netherlands Institute for Space Research)

Source: ScienceDaily

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ScienceDaily (Jan. 15, 2010) — The back up system of HIFI, the state of the art Dutch space instrument on ESA's Herschel space telescope, has been switched on successfully. Due to an unexpected voltage peak in the electronic system HIFI has been inactive for more than 160 days, but on Thursday evening 14 January Mission Control in Darmstadt confirmed that HIFI is now fully capable of performing groundbreaking observations in space again.

The coming three years HIFI, built under the supervision of SRON Netherlands Institute for Space Research, will investigate the physics and chemistry of interstellar clouds of gas and dust. The infrared spectrometer will chart the amount of carbon and water in these gas clouds, which is expected to shed new light on the birth and early development of stars and planets.
Finally, after months of tension and hard work, the engineers and researchers of SRON, the HIFI partners and the European Space Agency (ESA) could breathe freely again that Thursday evening. After some minor last obstacles had been overcome -- it took an extra day warming up the back-up Local Oscillator Control Unit (the module in which the malfunction took place) to a degree that would ensure that the switch on would bear no risks whatsoever -- HIFI is now in full swing again. Just like most space instruments HIFI has a back up system in case of a failure in the electronic system, and all tests have shown convincingly that the control units of the back up system function perfectly. Moreover, the sensors of HIFI perform on the same high level as in the beginning of August 2009, when the infrared spectrometer astonished the scientific community with the first, crystal clear observations of ionized carbon, the most challenging aspect of the measurement programme.

Strange readings:
The first indication that something was wrong with HIFI came from mission control in Darmstad on 3 August 2009. "Groningen, we have a problem." In the daily communications with Herschel/HIFI strange readings had been received. HIFI was in a state that was not described in the manuals. After months of intensive investigations and deliberations only one consistent scenario for this anomaly remained. Due to an unknown cause -- possibly a cosmic ray hit in the computer memory of one of the auxiliary computers- the processor of the Local Oscillator Control Unit (LCU) detected an error, rebooted and lost communication with the instrument's main computer. In this process after a little over a second inadvertently the standby switch was activated. This standby switch has been designed to protect the LCU against power drops on the main power line from the satellite, but now fully powered sent a voltage peak through the system. This peak was fatal for one of the diodes in one of the LCU DC/DC convertors.
The past months scientist from ESA, SRON and the HIFI partners have worked intensively to first determine the nature of the problem, and then on the necessary changes in the software to monitor the integrity of the computer memory and to prevent the malfunction from happening again. The first task in this process was to disable the standby switch that normally protects the Local Oscillator Control Unit (LCU) against sudden power drops. Normally it protects the precious Local Oscillator chains but now it got activated at the wrong moment. It was also necessary to subdue or eliminate any remaining voltage peaks in the system. The team achieved this by cutting back in all relay switching activities. Finally a software change ensured that communications with the LCUwill not be disturbed again."

Complex technological puzzle:
HIFI Project leader Peter Roelfsema: "It turned out to be a very complex technological puzzle that we had to solve based on limited information and under a great deal of pressure. But for all researchers involved, quickly finding an answer to this question was a matter of professional pride. We had to -- and would -- crack the problem with HIFI as soon as humanly possible, but we also had to take the time to be thourough. Scientists all over the world were waiting on the observations from HIFI. There are no certainties in space research; instruments that have to do precision work in the hostile environment of space will always be vulnerable. But we are confident that HIFI can now carry out all scientific observations."
The scientific observations focus on the quest for ionized carbon and water in the Universe. Principal investigator Frank Helmich says: "Ionized Carbon is important to astronomers because it is a good idicator for the warming up and cooling down of the gas from which stars and planets take shape. Therefore with HIFI we get a better idea of how the 'thermostat' of the Universe works. Water is probably the lubricant of the proces which gives birth to stars and planets. The molecule takes care of cooling extremely hot gases -- just like ionized carbon -- which enables them to concentrate to new suns. And HIFI also charts the atmospheres of planets and comets in our solar system. All in all we count on a rich scientific output again. This is really thanks to the great efforts made by all of the researchers at ESA, SRON and the HIFI partners, who have worked together as a single team. The motivation to crack this problem came from the depths of the professional pride of the staff themselves. While I hadn't expected anything else, I'm really very proud of this."

Story Source:
Adapted from materials provided by SRON Netherlands Institute for Space Research.

As the Crust Turns: Cassini Data Show Enceladus in Motion.

On Oct. 5, 2008, just after coming within 25 kilometers (15.6 miles) of the surface of Enceladus, NASA's Cassini captured this stunning mosaic as the spacecraft sped away from this geologically active moon of Saturn. (Credit: NASA/JPL/Space Science Institute)

Source: ScienceDaily
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ScienceDaily (Jan. 15, 2010) — Blobs of warm ice that periodically rise to the surface and churn the icy crust on Saturn's moon Enceladus explain the quirky heat behavior and intriguing surface of the moon's south polar region, according to a new paper using data from NASA's Cassini spacecraft.

"Cassini appears to have caught Enceladus in the middle of a burp," said Francis Nimmo, a planetary scientist at the University of California Santa Cruz and a co-author of the new paper in Nature Geoscience. "These tumultuous periods are rare and Cassini happens to have been watching the moon during one of these special epochs."
The south polar region captivates scientists because it hosts the fissures known as "tiger stripes" that spray water vapor and other particles out from the moon. While the latest paper, released on Jan. 10, doesn't link the churning and resurfacing directly to the formation of fissures and jets, it does fill in some of the blanks in the region's history.
"This episodic model helps to solve one of the most perplexing mysteries of Enceladus," said Bob Pappalardo, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., of the research done by his colleagues. "Why is the south polar surface so young? How could this amount of heat be pumped out at the moon's south pole? This idea assembles the pieces of the puzzle."
About four years ago, Cassini's composite infrared spectrometer instrument detected a heat flow in the south polar region of at least 6 gigawatts, the equivalent of at least a dozen electric power plants. This is at least three times as much heat as an average region of Earth of similar area would produce, despite Enceladus' small size. The region was also later found by Cassini's ion and neutral mass spectrometer instrument to be swiftly expelling argon, which comes from rocks decaying radioactively and has a well-known rate of decay.
Calculations told scientists it would be impossible for Enceladus to have continually produced heat and gas at this rate. Tidal movement -- the pull and push from Saturn as Enceladus moves around the planet -- cannot explain the release of so much energy.
The surface ages of different regions of Enceladus also show great diversity. Heavily cratered plains in the northern part of the moon appear to be as old as 4.2 billion years, while a region near the equator known as Sarandib Planitia is between 170 million and 3.7 billion years old. The south polar area, however, appears to be less than 100 million years old, possibly as young as 500,000 years.
Craig O'Neill of Macquarie University in Sydney, Australia, and Nimmo, who was partially funded by the NASA Outer Planets Research program, adapted a model that O'Neill had developed for the convection of Earth's crust. For Enceladus, which has a surface completely covered in cold ice that is fractured by the tug of Saturn's gravitational pull, the scientists stiffened up the crust. They picked a strength somewhere between that of the malleable tectonic plates on Earth and the rigid plates of Venus, which are so strong, it appears they never get sucked down into the interior.
Their model showed that heat building up from the interior of Enceladus could be released in episodic bubbles of warm, light ice rising to the surface, akin to the rising blobs of heated wax in a lava lamp. The rise of the warm bubbles would send cold, heavier ice down into the interior. (Warm is, of course, relative. Nimmo said the bubbles are probably just below freezing, which is 273 degrees Kelvin or 32 degrees Farenheit, whereas the surface is a frigid 80 degrees Kelvin or -316 degrees Farenheit.)
The model fits the activity on Enceladus when the churning and resurfacing periods are assumed to last about 10 million years, and the quiet periods, when the surface ice is undisturbed, last about 100 million to two billion years. Their model suggests the active periods have occurred only 1 to 10 percent of the time that Enceladus has existed and have recycled 10 to 40 percent of the surface. The active area around Enceladus's south pole is about 10 percent of its surface.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The Cassini orbiter was designed, developed and assembled at JPL.

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Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Sky Map: Solar Scientists Use 'Magnetic Mirror Effect' to Reproduce IBEX Observation.

These two maps show the entire sky in the emission of neutral hydrogen. The energetic neutral atom (ENA) measurements by the IBEX mission (bottom image) show a ribbon feature spanning across the entire sky. A group of solar physicists led by Jacob Heerikhuisen discovered that this feature can be closely reproduced by sophisticated models (top image) after adding an unpredicted "mirror effect." The two images show modeled and observed ENAs, respectively, at comparable speeds. (Credit: Heerikhuisen et al.)

Source: ScienceDaily

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ScienceDaily (Jan. 15, 2010) — Ever since NASA's Interstellar Boundary Explorer, or IBEX, mission scientists released the first comprehensive sky map of our solar system's edge in particles, solar physicists have been busy revising their models to account for the discovery of a narrow "ribbon" of bright emission that was completely unexpected and not predicted by any model at the time.

Further study by a team of scientists funded through NASA's Heliophysics Guest Investigator program has produced a revised model that explains and closely reproduces the IBEX result by incorporating a single new effect into an existing model. The new effect, put forward by the IBEX team soon after sighting of the ribbon, is that the magnetic field surrounding our solar system -- called the local galactic magnetic field -- acts like a mirror for the particles that IBEX sees.
The results appear in the January 10 issue of the Astrophysical Journal Letters. Jacob Heerikhuisen, a solar physicist at the University of Alabama in Huntsville, is the lead author of the paper. Heerikhuisen and his colleagues believe the orientation of the local galactic magnetic field is closely related to the location of the ribbon in the sky.
Charged particles "orbit" magnetic field lines. When they suddenly lose their charge, they fly off in a straight line maintaining their current direction. Only particles that orbit the magnetic mirror, where it faces us directly, can flow back toward us and are captured by IBEX.
These particles originate in our magnetized solar system, or heliosphere -- the region from the sun to where the solar wind meets the local interstellar medium (LISM). First these particles lose their charge and fly out of the heliosphere. At some distance they charge again and start "orbiting" a field line of the local interstellar magnetic field, where they get "recycled" by losing their charge again.
Solar physicists did not expect this "mirror effect," which is "somewhat analogous to exploring an unknown cave," says Arik Posner, IBEX program scientist at NASA Headquarters. "By activating IBEX, we suddenly see that the solar system has a lit candle and see its light reflected in the 'cave walls' shining back at us," says Posner. "What we find is that the 'cave wall' acts more like a faint mirror than like a normal wall," he adds.
What we saw with IBEX is that this "cave" we are exploring apparently has very straight and smooth magnetic walls, being shaped somewhat like a subway tunnel. IBEX can remotely observe the direction of the local interstellar magnetic field and may observe whether it stays the same or changes over time.
The sun's presence affects the local interstellar magnetic field, bulging the field out to form something larger that is similar to a subway station. However, the "station" itself, our heliosphere, slowly moves along the tunnel, not subway cars.
Straight magnetic field lines are only found in plasmas where the magnetic field is strong and shapes the flow of particles, such as the smooth magnetic loops observed in the sun's corona.
The IBEX results appear consistent with a recent finding by the Voyager mission that the surrounding galactic magnetic field in the LISM is much stronger than previously thought.
Assuming this "magnetic mirror effect" produces the narrow "ribbon" discovered by IBEX, then the orientation of the local galactic magnetic field is closely related to the location of the ribbon. With the help of global 3D models, this mechanism could help accurately determine the magnetic field's direction. The finding would also suggest that IBEX is detecting the particles from both inside and outside the heliopause, which is the boundary region between the outer solar system and the local interstellar medium.
"The IBEX mission has from the outset stressed both the criticality of new measurements and the collaboration between observations and theoretical research," explains Robert MacDowall, IBEX mission scientist at NASA Goddard. "The discovery by Heerikhuisen and colleagues demonstrates how successful this approach can be."

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Adapted from materials provided by NASA/Goddard Space Flight Center.

Radio pulses from pulsar appear to move faster than light.

A diagram of a pulsar, showing its rotation axis and its magnetic axis. Image: NASA

Source: Physorg.com

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Laboratory experiments in the last few decades have shown that some things can appear to move faster than light without contradicting Einstein's special theory of relativity, but now astrophysicists have seen real examples of superluminal speeds in the form of radio pulses from a pulsar.

Superluminal, or faster than light, speeds are associated with anomalous dispersion, which is a process in which the refractive index of a medium increases with the wavelength of light passing through it. If a light pulse (consisting of a group of light waves at different wavelengths) passes through such a medium, the group velocity of the pulse can increase to a velocity greater than any of the waves within the pulse, but the energy of the pulse still travels at the speed of light, which means information is transmitted in accordance with Einstein's theory.
Astrophysicists, led by Frederick Jenet of the University of Texas at Brownsville, have been monitoring a pulsar, PSR B1937+21, which is about 10,000 light years from Earth. They used the Arecibo Observatory in Puerto Rico to obtain radio data over three days at 1420.4 MHz with a bandwidth of 1.5 MHz. They found that pulses closer to the center arrived earlier than the normal timing, which suggests they had travelled faster than the speed of light.
A pulsar is a neutron star that is spinning rapidly and emitting a rotating beam of radio radiation as it spins, which is observed on Earth at regular intervals rather like light from a lighthouse. The pulses of radiation can be affected by several factors as they travel through the interstellar medium (ISM). Their polarization can be rotated if they pass through a magnetic field, for example, and they can be scattered if they encounter free electrons, and can be absorbed by neutral hydrogen in the ISM. Jenet and his colleagues think anomalous dispersion also affects the pulses.
According to Jenet and colleagues, the pulses from the pulsar traveled through a cloud of neutral hydrogen, which has a resonance of 1420.4 MHz -- the exact center of the bandwidth studied. Passing through the cloud caused anomalous dispersion that resulted in a superluminal group velocity, and pulses with frequencies closest to the resonance frequency arrived earlier than other pulses.
The scientists believe the pulses appear to travel faster than light because of an "interplay between the time scales present in the pulse and the time scales present in the medium." The faster-than-light pulses do not violate Einstein's theory because technically the pulse carries no information. The effect has been known in laboratory experiments, but these observations were the first in an astrophysical context.
The findings, to be published in the Astrophysical Journal, could help astronomers gain a more complete understanding of the composition of space in the regions between stars, and in particular the properties of neutral hydrogen clouds in our galaxy.
More information: A preprint of the article is available at http://arxiv.org/abs/0909.2445v2 .

Second Smallest Exoplanet Spotted: Discovery Highlights New Potential for Eventually Finding Earth-Mass Planets.

Astronomers have detected an extrasolar planet with a mass just four times that of Earth. (Credit: L. Calcada, ESO)

Source: ScienceDaily

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ScienceDaily (Jan. 14, 2010) — Astronomers from the California Institute of Technology (Caltech) and other institutions, using the highly sensitive 10-meter Keck I telescope atop Hawaii's Mauna Kea, have detected an extrasolar planet with a mass just four times that of Earth. The planet, which orbits its parent star HD156668 about once every four days, is the second-smallest world among the more than 400 exoplanets (planets located outside our solar system) that have been found to date. It is located approximately 80 light-years from Earth in the direction of the constellation Hercules.

The find, made possible through NASA's Eta-Earth Survey for Low-Mass Planets was announced at the 215th American Astronomical Society meeting held January 4-7, 2010, in Washington, D.C.
Dubbed HD 156668b, the planet -- a so-called "super Earth" that would glow with blast-furnace-like temperatures -- offers a tantalizing hint of discoveries yet to come. Astronomers hope those discoveries will include Earth-size planets located in the "habitable zone," the area roughly the distance from the earth to the sun, and thus potentially favorable to life.
HD 156668b was discovered with the radial velocity or wobble method, which relies on Keck's High Resolution Echelle Spectrometer (HIRES) to spread light collected from the telescope into its component wavelengths or colors, producing a spectrum. As the planet orbits the star, it causes the star to move back and forth along our line of sight, which causes the starlight to become redder and then bluer in a periodic fashion.
The color shifts give astronomers the mass of the planet and the characteristics of its orbit, such as how much time it takes to orbit the star. The majority of the exoplanets discovered have been found in this way.
The discovery of low-mass planets like HD 156668b has become possible due to the development of techniques to watch stars wobble with increasing clarity, and of software that can pluck the signals of increasingly smaller planets from amid the 'noise' made by their pulsating, wobbling parent stars.
"If the stars themselves have imperfections and are unstable, their wobbling would cause jumps in velocity that could mimic or hide the existence of a planet," says John A. Johnson, assistant professor of astronomy at Caltech and codiscoverer of the new planet along with Andrew Howard and Geoff Marcy of the University of California at Berkeley, Debra Fischer of Yale University, Jason Wright of Penn State University, and the members of the California Planet Survey collaboration.
"We have been doing simulations to understand the astrophysics of these imperfections, and how to distinguish them from the signals from a planet," says Johnson. "We hope to use these simulations to design even better observing strategies and data-analysis techniques."
The discovery of a planet that is comparable in size to Earth and found within the habitable zone, however, "will require a great deal of work," he says. "If we could build the best possible radial-velocity instrument tomorrow, we might have answers in three years, and a solid census of Earthlike planets within a decade. We'll need gigantic leaps in sensitivity to get there, and we're hot on the trail."
Johnson is also currently building a new camera for the 60-inch telescope at Caltech's Palomar Observatory. The camera will allow astronomers to search for the passages -- or transits -- of low-mass planets like HD156668 across the faces of their stars.
"If we catch the planet in transit, we can measure the planet's radius and density, and therefore address the question of whether the planet has a composition more like Earth, with a solid surface and thin atmosphere, or is a miniature version of Neptune, with a heavy gaseous atmosphere," he says.
The Keck I telescope is part of the Keck Observatory, a joint effort of Caltech and the University of California.
For more information about extrasolar planet discoveries, visit http://exoplanets.org.

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Adapted from materials provided by California Institute of Technology.

Giant Magnetic Loop Sweeps Through Space Between Stellar Pair.

Artist's conception of Algol star system with radio image superimposed on grid. (Credit: Peterson et al., NRAO/AUI/NSF)

Source: ScienceDaily

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ScienceDaily (Jan. 14, 2010) — Astronomers have found a giant magnetic loop stretched outward from one of the stars making up the famous double-star system Algol. The scientists used an international collection of radio telescopes to discover the feature, which may help explain details of previous observations of the stellar system.

"This is the first time we've seen a feature like this in the magnetic field of any star other than the Sun," said William Peterson, of the University of Iowa.
The pair, 93 light-years from Earth, includes a star about 3 times more massive than the Sun and a less-massive companion, orbiting it at a distance of 5.8 million miles, only about six percent of the distance between Earth and the Sun. The newly-discovered magnetic loop emerges from the poles of the less-massive star and stretches outward in the direction of the primary star. As the secondary star orbits its companion, one side -- the side with the magnetic loop -- constantly faces the more-massive star, just as the same side of our Moon always faces the Earth.
The scientists detected the magnetic loop by making extremely detailed images of the system using an intercontinental set of radio telescopes, including the National Science Foundation's Very Long Baseline Array, Very Large Array, and Robert C. Byrd Green Bank Telescope, along with the Effelsberg radio telescope in Germany. These radio telescopes were used as a single observing system that offered both great detail, or resolving power, and high sensitivity to detect very faint radio waves. When working together, these telescopes are known as the High Sensitivity Array.
Algol, in the constellation Perseus, is visible to the naked eye and well-known to amateur astronomers. As seen from Earth, the two stars regularly pass in front of each other, causing a notable change in brightness. The pair completes a cycle of such eclipses in less than three days, making it a popular object for amateur observers. The variability in brightness was discovered by an Italian astronomer in 1667, and the eclipsing-binary explanation was confirmed in 1889.
The newly-discovered magnetic loop helps explain phenomena seen in earlier observations of the Algol system at X-ray and radio wavelengths, the scientists said. In addition, they now believe there may be similar magnetic features in other double-star systems.
Peterson worked with Robert Mutel, also of the University of Iowa, Manuel Gudel of the Swiss Federal Institute of Technology, and Miller Goss of the National Radio Astronomy Observatory. The scientists reported their findings in the 14 January edition of the scientific journal Nature.

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Adapted from materials provided by National Radio Astronomy Observatory.

How Galaxies Form: New Research Resolves Conflict in Theory.

These images depict various stages of galaxy formation under the cold dark matter theory using new computer simulations that account for the effects of supernova explosions. (Credit: Katy Brooks)

Source: ScienceDaily

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ScienceDaily (Jan. 14, 2010) — For more than two decades, the cold dark matter theory has been used by cosmologists to explain how the smooth universe born in the big bang more than 13 billion years ago evolved into the filamentary, galaxy-rich cosmic web that we see today.

There's been just one problem: the theory suggested most galaxies should have far more stars and dark matter at their cores than they actually do. The problem is most pronounced for dwarf galaxies, the most common galaxies in our own celestial neighborhood. Each contains less than 1 percent of the stars found in large galaxies such as the Milky Way.
Now an international research team, led by a University of Washington astronomer, reports Jan. 14 in Nature that it resolved the problem using millions of hours on supercomputers to run simulations of galaxy formation (1 million hours is more than 100 years). The simulations produced dwarf galaxies very much like those observed today by satellites and large telescopes around the world.
"Most previous work included only a simple description of how and where stars formed within galaxies, or neglected star formation altogether," said Fabio Governato, a UW research associate professor of astronomy and lead author of the Nature paper.
"Instead we performed new computer simulations, run over several national supercomputing facilities, and included a better description of where and how star formation happens in galaxies."
The simulations showed that as the most massive new stars exploded as supernovas, the blasts generated enormous winds that swept huge amounts of gas away from the center of what would become dwarf galaxies, preventing millions of new stars from forming.
With so much mass suddenly removed from the center of the galaxy, the pull of gravity on the dark matter there is diminished and the dark matter drifts away, Governato said. It is similar to what would happen if our sun suddenly disappeared and the loss of its gravitational pull allowed the Earth to drift off into space.
The cosmic explosions proved to be the missing piece of the puzzle, and adding them to the simulations generated formation of galaxies with substantially lower densities at their cores, closely matching the observed properties of dwarf galaxies.
"The cold dark matter theory works amazingly well at telling where, when and how many galaxies should form," Governato said. "What we did was find a better description of processes that we know happen in the real universe, resulting in more accurate simulations."
The theory of cold dark matter, first advanced in the mid 1980s, holds that the vast majority of the matter in the universe -- as much as 75 percent -- is made up of "dark" material that does not interact with electrons and protons and so cannot be observed from electromagnetic radiation. The term "cold" means that immediately following the big bang these dark matter particles have speeds far lower than the speed of light.
In the cold dark matter theory, smaller structures form first, then they merge with each other to form more massive halos, and finally galaxies form within the halos.
Coauthors of the Nature paper are Chris Brook of the Jeremiah Horrocks Institute in the United Kingdom; Lucio Mayer of the Institut für Astronomie and the Institute for Theoretical Physics in Switzerland; Alyson Brooks of the California Institute of Technology; George Rhee of the University of Nevada; James Wadsley and Gregory Stinson of McMaster University in Canada; Patrik Jonsson and Piero Madau of the University of California, Santa Cruz; Beth Willman of Haverford College in Pennsylvania and Thomas R. Quinn of the UW.
The research was funded by NASA and the National Science Foundation, and was conducted using facilities of NASA's Advanced Supercomputing Division, the University of Washington Computing Center, the Arctic Region Supercomputing Center in Alaska and the TeraGrid supercomputer coordinated through the Grid Infrastructure Group at the University of Chicago.

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Adapted from materials provided by University of Washington.

Astronomers Capture First Direct Spectrum of an Exoplanet.

By studying a triple planetary system that resembles a scaled-up version of our own Sun’s family of planets, astronomers have been able to obtain the first direct spectrum of a planet around a star, thus bringing new insights into its formation and composition. The spectrum is that of a giant exoplanet, orbiting around the bright and very young star HR 8799, about 130 light-years away. This montage shows the image and the spectrum of the star and the planet as seen with the NACO adaptive optics instrument on ESO’s Very Large Telescope. (Credit: ESO/M. Janson)

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ScienceDaily

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ScienceDaily (Jan. 13, 2010) — By studying a triple planetary system that resembles a scaled-up version of our own Sun's family of planets, astronomers have been able to obtain the first direct spectrum -- the "chemical fingerprint" [1] -- of a planet orbiting a distant star [2], thus bringing new insights into the planet's formation and composition. The result represents a milestone in the search for life elsewhere in the Universe.

"The spectrum of a planet is like a fingerprint. It provides key information about the chemical elements in the planet's atmosphere," says Markus Janson, lead author of a paper reporting the new findings. "With this information, we can better understand how the planet formed and, in the future, we might even be able to find tell-tale signs of the presence of life."
The researchers obtained the spectrum of a giant exoplanet that orbits the bright, very young star HR 8799. The system is at about 130 light-years from Earth. The star has 1.5 times the mass of the Sun, and hosts a planetary system that resembles a scaled-up model of our own Solar System. Three giant companion planets were detected in 2008 by another team of researchers, with masses between 7 and 10 times that of Jupiter. They are between 20 and 70 times as far from their host star as the Earth is from the Sun; the system also features two belts of smaller objects, similar to our Solar System's asteroid and Kuiper belts.
"Our target was the middle planet of the three, which is roughly ten times more massive than Jupiter and has a temperature of about 800 degrees Celsius," says team member Carolina Bergfors. "After more than five hours of exposure time, we were able to tease out the planet's spectrum from the host star's much brighter light."
This is the first time the spectrum of an exoplanet orbiting a normal, almost Sun-like star has been obtained directly. Previously, the only spectra to be obtained required a space telescope to watch an exoplanet pass directly behind its host star in an "exoplanetary eclipse," and then the spectrum could be extracted by comparing the light of the star before and after. However, this method can only be applied if the orientation of the exoplanet's orbit is exactly right, which is true for only a small fraction of all exoplanetary systems. The present spectrum, on the other hand, was obtained from the ground, using ESO's Very Large Telescope (VLT), in direct observations that do not depend on the orbit's orientation.
As the host star is several thousand times brighter than the planet, this is a remarkable achievement. "It's like trying to see what a candle is made of, by observing it from a distance of two kilometres when it's next to a blindingly bright 300 Watt lamp," says Janson.
The discovery was made possible by the infrared instrument NACO, mounted on the VLT, and relied heavily on the extraordinary capabilities of the instrument's adaptive optics system [3]. Even more precise images and spectra of giant exoplanets are expected both from the next generation instrument SPHERE, to be installed on the VLT in 2011, and from the European Extremely Large Telescope.
The newly collected data show that the atmosphere enclosing the planet is still poorly understood. "The features observed in the spectrum are not compatible with current theoretical models," explains co-author Wolfgang Brandner. "We need to take into account a more detailed description of the atmospheric dust clouds, or accept that the atmosphere has a different chemical composition from that previously assumed."
The astronomers hope to soon get their hands on the fingerprints of the other two giant planets so they can compare, for the first time, the spectra of three planets belonging to the same system. "This will surely shed new light on the processes that lead to the formation of planetary systems like our own," concludes Janson.

Notes:
[1] As every rainbow demonstrates, white light can be split up into different colours. Astronomers artificially split up the light they receive from distant objects into its different colours (or "wavelengths"). However, where we distinguish five or six rainbow colours, astronomers map hundreds of finely nuanced colours, producing a spectrum -- a record of the different amounts of light the object emits in each narrow colour band. The details of the spectrum -- more light emitted at some colours, less light at others -- provide tell-tale signs about the chemical composition of the matter producing the light. This makes spectroscopy, the recording of spectra, an important investigative tool in astronomy.
[2] In 2004, astronomers used NACO on the VLT to obtain an image and a spectrum of a 5 Jupiter mass object around a brown dwarf -- a "failed star." It is however thought that the pair probably formed together, like a petite stellar binary, instead of the companion forming in the disc around the brown dwarf, like a star-planet system.
[3] Telescopes on the ground suffer from a blurring effect introduced by atmospheric turbulence. This turbulence causes the stars to twinkle in a way that delights poets but frustrates astronomers, since it smears out the fine details of the images. However, with adaptive optics techniques, this major drawback can be overcome so that the telescope produces images that are as sharp as theoretically possible, i.e. approaching conditions in space. Adaptive optics systems work by means of a computer-controlled deformable mirror that counteracts the image distortion introduced by atmospheric turbulence. It is based on real-time optical corrections computed at very high speed (several hundreds of times each second) from image data obtained by a wavefront sensor (a special camera) that monitors light from a reference star.

More information:
This research was presented in a paper in press as a Letter to the Astrophysical Journal ("Spatially resolved spectroscopy of the exoplanet HR 8799 c," by M. Janson et al.).
The team is composed of M. Janson (University of Toronto, Canada), C. Bergfors, M. Goto, W. Brandner (Max-Planck-Institute for Astronomy, Heidelberg, Germany) and D. Lafrenière (University of Montreal, Canada). Preparatory data were taken with the IRCS instrument at the Subaru telescope.

Story Source:
Adapted from materials provided by ESO.
Journal Reference:
1. M. Janson et al. Spatially resolved spectroscopy of the exoplanet HR 8799 c. Astrophysical Journal, 2010 (in press).

Across the Multiverse: Physicist Considers the Big Picture.

Source: ScienceDaily

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ScienceDaily (Jan. 13, 2010) — Is there anybody out there? In Alejandro Jenkins' case, the question refers not to whether life exists elsewhere in the universe, but whether it exists in other universes outside of our own.

While that might be a mind-blowing concept for the layperson to ponder, it's all in a day's work for Jenkins, a postdoctoral associate in theoretical high-energy physics at The Florida State University. In fact, his deep thoughts on the hypothetical "multiverse" -- think of it as a mega-universe full of numerous smaller universes, including our own -- are now receiving worldwide attention, thanks to a cover article he co-wrote for the January 2010 issue of Scientific American magazine.
In "Looking for Life in the Multiverse," Jenkins and co-writer Gilad Perez, a theorist at the Weizmann Institute of Science in Israel, discuss a provocative hypothesis known as the anthropic principle, which states that the existence of intelligent life (capable of studying physical processes) imposes constraints on the possible form of the laws of physics.
"Our lives here on Earth -- in fact, everything we see and know about the universe around us -- depend on a precise set of conditions that makes us possible," Jenkins said. "For example, if the fundamental forces that shape matter in our universe were altered even slightly, it's conceivable that atoms never would have formed, or that the element carbon, which is considered a basic building block of life as we know it, wouldn't exist. So how is it that such a perfect balance exists? Some would attribute it to God, but of course, that is outside the realm of physics."
The theory of "cosmic inflation," which was developed in the 1980s in order to solve certain puzzles about the structure of our universe, predicts that ours is just one of countless universes to emerge from the same primordial vacuum. We have no way of seeing those other universes, although many of the other predictions of cosmic inflation have recently been corroborated by astrophysical measurements.
Given some of science's current ideas about high-energy physics, it is plausible that those other universes might each have different physical interactions. So perhaps it's no mystery that we would happen to occupy the rare universe in which conditions are just right to make life possible. This is analogous to how, out of the many planets in our universe, we occupy the rare one where conditions are right for organic evolution.
"What theorists like Dr. Perez and I do is tweak the calculations of the fundamental forces in order to predict the resulting effects on possible, alternative universes," Jenkins said. "Some of these results are easy to predict; for example, if there was no electromagnetic force, there would be no atoms and no chemical bonds. And without gravity, matter wouldn't coalesce into planets, stars and galaxies.
"What is surprising about our results is that we found conditions that, while very different from those of our own universe, nevertheless might allow -- again, at least hypothetically -- for the existence of life. (What that life would look like is another story entirely.) This actually brings into question the usefulness of the anthropic principle when applied to particle physics, and might force us to think more carefully about what the multiverse would actually contain."
"Looking for Life in the Multiverse" can be purchased, or accessed by Scientific American subscribers, at the magazine's Web site. The January issue of the magazine is also on sale now throughout the United States.
"Having an article in Scientific American is a magnificent accomplishment, but being selected for the cover story is special indeed," said Mark Riley, chairman of the Department of Physics at Florida State. "My congratulations to Dr. Jenkins and our High Energy Physics Group."
Jenkins has degrees from Harvard University and the California Institute of Technology, and he previously conducted postgraduate research on the topic of alternative universes while at the Massachusetts Institute of Technology. Despite all of his training, however, the Scientific American article was unexpected.
"I am very proud of our research, but to be honest, I think that this had something to do with the fact that people are naturally intrigued by speculative ideas about cosmology and the 'big picture.'
"The idea of parallel universes, in particular, is one that many people find exciting," Jenkins said. "The current season of (the Fox-TV comedy) 'Family Guy' recently premiered with an episode called 'Road to the Multiverse,' which was premised on the idea that one can visit other universes -- although that seems impossible given what we know about physics. Nevertheless, whether other universes actually exist is a question that has consequences for our understanding of physics in this world. I think our research raises important questions in that regard."

Story Source:
Adapted from materials provided by Florida State University.

Journal Reference:
1.Alejandro Jenkins and Gilad Perez. Looking for Life in the Multiverse. Scientific American, 2010; 302 (1): 42 DOI: 10.1038/scientificamerican0110-42

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How Earth Survived Its Birth: New Simulation Reveals Planet Migration Prevents Plunge Into Sun.

Source: ScienceDaily

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ScienceDaily (Jan. 8, 2010) — For the last 20 years, the best models of planet formation -- or how planets grow from dust in a gas disk -- have contradicted the very existence of Earth. These models assumed locally constant temperatures within a disk, and the planets plunge into the Sun. Now, new simulations from researchers at the American Museum of Natural History and the University of Cambridge show that variations in temperature can lead to regions of outward and inward migration that safely trap planets on orbits.

When the protoplanetary disk begins to dissipate, planets are left behind, safe from impact with their parent star.
The results of this research are being presented at the 2010 meeting of the American Astronomical Society in Washington, D.C.
"We are trying to understand how planets interact with the gas disks from which they form as the disk evolves over its lifetime," says Mordecai-Mark Mac Low, Curator of Astrophysics and Division Chair of Physical Sciences at the Museum. "We show that the planetoids from which the Earth formed can survive their immersion in the gas disk without falling into the Sun."
During the birth of a star, a disk of gas and dust forms. The midplane of this dusty disk is opaque and cannot quickly cool by radiating heat to outer space. Until recently, no one has included temperature variation in models of planet formation.
Co-author Sijme-Jan Paardekooper of the University of Cambridge ran groundbreaking new simulations like that most recently published online (http://arxiv.org/abs/0909.4552). His work shows that the direction of migration of low-mass planets in disks depends on the detailed temperature structure of the disk. This key insight lays the groundwork for the current work.
The American Astronomical Society presentation incorporates the results of Paardekooper's local models into the long-term evolution of the temperature and density structure of a protoplanetary disk. The result of the simulation is that, over the lifetime of a disk, planets get trapped in orbits between regions of inward and outward migration. The orbits slowly move inward as the disk dissipates. Once the gas densities drop low enough for the planets to no longer be influenced by disk, the planets are dropped into an orbit similar to the orbits of planets around the Sun. The radius of the orbit at which a planet is released depends on its mass.
"We used a one-dimensional model for this project," says co-author Wladimir Lyra, a postdoctoral researcher in the Department of Astrophysics at the Museum. "Three dimensional models are so computationally expensive that we could only follow the evolution of disks for about 100 orbits -- about 1,000 years. We want to see what happens over the entire multimillion year lifetime of a disk."
Mac Low is presenting this research at the upcoming American Astronomical Society meetings in Washington, D.C. on January 6 with a press conference on the following day (January 7 at 10:30 am: "Spicing up the solar system.") A research paper is currently submitted to The Astrophysical Journal, authored by Lyra, Paardekooper, and Mac Low. This research was funded by the American Museum of Natural History, the National Science Foundation, and NASA.

Story Source:
Adapted from materials provided by American Museum of Natural History, via EurekAlert!, a service of AAAS.