Astronomy Cmarchesin

Releases from NASA, NASA Galex, NASA's Goddard Space Flight Center, Hubble, Hinode, Spitzer, Cassini, ESO, ESA, Chandra, HiRISE, Royal Astronomical Society, NRAO, Astronomy Picture of the Day, Harvard-Smithsonian Center For Astrophysics, etc.

Monday, August 30, 2010

Spectrum of Young Extrasolar Planet Yields Surprising Results

Keck II image of the young extrasolar planet HR 8799 b, seen as the point source in center of image. The bright light from the parent star HR 8799 is seen in background in yellow/red and has been removed in an annular region centered on the planet. Credit: Brendan Bowler and Michael Liu, IfA/Hawaii

The W. M. Keck Observatory operates two 10-meter optical/infrared telescopes on the summit of Mauna Kea on the island of Hawai’i and is a scientific partnership of the California Institute of Technology, the University of California and NASA. Credit: Pablo McLoud/WMKO

Kamuela, HI - Astronomers at the University of Hawaii have measured the temperature of a young gas-giant planet around another star using the W. M. Keck Observatory, and the results are puzzling. They have found that its atmosphere is unlike that of any previously studied extrasolar planet.

By obtaining a spectrum of its emitted light, the astronomers determined the temperature of the planet. As a result, they found that current theoretical models of gas-giant planets did a poor job of explaining all the data. The team suspects that the reason is dust in the planet’s atmosphere. Models with normal amounts of dust do not resemble this planet, but models with exceptionally thick dust clouds do a much better job. It therefore appears that young gas-giant planets are extremely cloudy.

“We are at a point where not only can we directly image planets around other stars, but we can begin to study the properties of their atmospheres in detail. Direct spectroscopy of exoplanets is the future of this field,” said Mr. Brendan Bowler, a graduate student at the University of Hawaii and the lead author of the study.

The planet, known as HR 8799 b, is one of three gas-giant planets orbiting the star HR 8799, located 130 light-years away from Earth in the constellation Pegasus. (For reference, the distance to the nearest nighttime star from Earth is about four light-years.) HR 8799 b is the lowest-mass planet around the star, about seven times the mass of Jupiter. This multiplanet system was discovered by direct imaging in 2008, and now, only a year and a half later, astronomers have obtained a spectrum of one of its planets. The spectrum of a planet contains much more information than a single image: it can reveal the temperature, chemical composition, and cloud properties of the planet.

The technique the team used to determine the planet’s temperature relies on the chemistry of the planet’s atmosphere. Specifically, the presence or absence of gaseous methane can be used as a thermometer. The team found that HR 8799 b shows little or no methane in its atmosphere. Based on their spectrum and previously obtained images of the planet, and by comparing the observations to theoretical models of low-temperature atmospheres, they estimate the coolest possible temperature for the planet is about 1200 Kelvin (about 1,700 degrees Fahrenheit).

The models, however, did a poor job of reproducing all the data. Current theoretical models predict HR 8799 b should be about 400 Kelvin cooler than they measured, based on the age of the planet and the amount of energy it is currently emitting. The team suspects the discrepancy arises because the planet is much more dusty and cloudy than expected by current models.

“Direct studies of extrasolar planets are just in their infancy. But even at this early stage, we are learning they are a different beast than objects we have known about previously,” said University of Hawaii astronomy professor Michael Liu, coauthor of the study.

The planets around HR 8799 are incredibly faint, about 100,000 times dimmer than their parent star. To obtain the spectrum of HR 8799 b, the team relied on the adaptive optics system of the Keck II Telescope to make an ultra-sharp image of the star for many hours. Then they used the Keck facility instrument called OSIRIS, a special kind of spectrograph, to precisely separate the spectrum of the planet from the light of its parent star.

“Adaptive optics systems on Keck and other large ground-based telescopes make sharper images than even the Hubble Space Telescope. With adaptive optics, we are learning an incredible amount about objects that are smaller than the lowest-mass stars and larger than the most massive gas-giant planets in our solar system,” said Mr. Trent Dupuy, a University of Hawaii graduate student and co-author on the study. Dr. Michael Cushing of the Jet Propulsion Laboratory was also a member of the team announcing these results.

Although over 500 planets have been discovered around other stars, only six planets have been directly imaged. Three of these are around HR 8799 and were discovered in 2008 by Christian Marois of Canada’s National Research Council and collaborators. When it was announced, the discovery represented one of the first direct image of light emitted from extrasolar planets.

A paper describing the study will be published in the Astrophysical Journal later this year. A copy is available here http://arxiv.org/abs/1008.4582.

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Abell 1758: Cluster Collisions Switch on Radio Halos

Abell 1758
Credit X-ray (NASA/CXC/SAO/M.Markevitch);
Radio (TIFR/GMRTSAO/INAF/R.Cassano, S.Giacintucci);
Optical (DSS)



This is a composite image of the northern part of the galaxy cluster Abell 1758, located about 3.2 billion light years from Earth, showing the effects of a collision between two smaller galaxy clusters. Chandra X-ray data (blue) reveals hot gas in the cluster and data from the Giant Metrewave Radio Telescope (GMRT) in India (pink) shows huge "halos" generated by ultra-relativistic particles and magnetic fields over vast scales. Optical data from the Digitized Sky Survey are colored gold.

A study of this galaxy cluster and 31 others with Chandra and the GMRT shows that huge radio halos are generated during collisions between galaxy clusters. This result implies that galaxy clusters with radio halos are still forming, while clusters without this radio emission are not still accumulating large amounts of material. The result also implies that relativistic electrons are likely accelerated by turbulence generated by mergers between clusters

Galaxy clusters are the largest structures in the Universe that are bound together by gravity. They form when smaller clusters or groups of galaxies collide and merge. Collisions between galaxy clusters, such as this one in Abell 1758 and its more famous cousin the Bullet Cluster, are the most energetic events in the Universe since the Big Bang. Their growth rate over the last 7 billion years has been slowed by the effects of dark energy, as shown by previous studies with Chandra.

Fast Facts for Abell 1758:

Scale: Image is about 13 arcmin across (about 12 million light years)
Category:
Groups & Clusters of Galaxies, Cosmology/Deep Fields/X-ray Background
Coordinates: (J2000) RA 13h 32m 43.20s | Dec +50° 32' 25.70"
Constellation:
Canes Venatici
Observation Date: Aug 28, 2001
Observation Time: 16 hours 40 min
Obs. ID: 2213
Color Code: X-ray (Blue); Radio (Pink); Optical (Gold)
Instrument:
ACIS
Distance Estimate: 3.2 Billion Light Years (z=0.28)

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Friday, August 27, 2010

Watch Titan Occult a Binary Star System

It is Astrophoto Friday! This week's image shows a unique event that was captured by the 200-inch Hale Telescope armed with adaptive optics.


What might look like Pac Man swallowing a dot is actually Saturn's moon Titan occulting (passing in front of) a binary star system (named NV0435215+200905). The two stars are separated in the sky by just 1.5 arc seconds (One arc second is 1/3600 of a degree).

Because fantastic resolving power of the Hale using adaptive optics you can see that the light of the star nearest to Titan is being refracted by Titan's dense atmosphere. Such events are rare, but valuable. The starlight as it is seen passing through Titan's atmosphere is essentially a probe providing clues as to the density, temperature and wind patterns of this distant world. The team of astronomers (Antonin Bouchez, Michael E. Brown, Mitchell Troy, Rick S. Burruss, Richard G. Dekany and Robert A. West) that observed this event December 20, 2001 was fortunate that both of the stars were seen to pass behind Titan. This provided two passes through Titan's atmosphere - effectively doubling what could be learned from the event.

Be sure to check out the movie of the event. As you watch it will look like Titan is still and the stars are moving behind it. As they pass behind Titan be sure to look for the refracted light of each star on either side of Titan's atmosphere. It is an impressive sight!

The result? Jet stream winds were discovered in Titan's atmosphere.

For those so inclined you can read a pdf of one of the scientific publication that came out of these observations.

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Thursday, August 26, 2010

NASA's Kepler Mission Discovers Two Planets Transiting the Same Star

Worlds on the Edge
This artist’s concept illustrates the two Saturn-sized planets discovered by NASA’s Kepler mission. The star system is oriented edge-on, as seen by Kepler, such that both planets cross in front, or transit, their star, named Kepler-9. This is the first star system found to have multiple transiting planets. Image credit: NASA/Ames/JPL-Caltech. Click image for full-resolution

MOFFETT FIELD, Calif. -- NASA's Kepler spacecraft has discovered the first confirmed planetary system with more than one planet crossing in front of, or transiting, the same star.

The transit signatures of two distinct planets were seen in the data for the sun-like star designated Kepler-9. The planets were named Kepler-9b and 9c. The discovery incorporates seven months of observations of more than 156,000 stars as part of an ongoing search for Earth-sized planets outside our solar system. The findings will be published in Thursday's issue of the journal Science.

Kepler's ultra-precise camera measures tiny decreases in the stars' brightness that occur when a planet transits them. The size of the planet can be derived from these temporary dips.

The distance of the planet from the star can be calculated by measuring the time between successive dips as the planet orbits the star. Small variations in the regularity of these dips can be used to determine the masses of planets and detect other non-transiting planets in the system.

In June, mission scientists submitted findings for peer review that identified more than 700 planet candidates in the first 43 days of Kepler data. The data included five additional candidate systems that appear to exhibit more than one transiting planet. The Kepler team recently identified a sixth target exhibiting multiple transits and accumulated enough follow-up data to confirm this multi-planet system.

"Kepler's high quality data and round-the-clock coverage of transiting objects enable a whole host of unique measurements to be made of the parent stars and their planetary systems," said Doug Hudgins, the Kepler program scientist at NASA Headquarters in Washington.

Scientists refined the estimates of the masses of the planets using observations from the W.M. Keck Observatory in Hawaii. The observations show Kepler-9b is the larger of the two planets, and both have masses similar to but less than Saturn. Kepler-9b lies closest to the star with an orbit of about 19 days, while Kepler-9c has an orbit of about 38 days. By observing several transits by each planet over the seven months of data, the time between successive transits could be analyzed.

"This discovery is the first clear detection of significant changes in the intervals from one planetary transit to the next, what we call transit timing variations," said Matthew Holman, a Kepler mission scientist from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "This is evidence of the gravitational interaction between the two planets as seen by the Kepler spacecraft."

In addition to the two confirmed giant planets, Kepler scientists also have identified what appears to be a third, much smaller transit signature in the observations of Kepler-9. That signature is consistent with the transits of a super-Earth-sized planet about 1.5 times the radius of Earth in a scorching, near-sun 1.6 day-orbit. Additional observations are required to determine whether this signal is indeed a planet or an astronomical phenomenon that mimics the appearance of a transit.

NASA's Ames Research Center in Moffett Field, Calif., manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development.

Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data.

For more information about the Kepler mission, visit: http://www.nasa.gov/kepler

Contacts

J.D. Harrington
Headquarters, Washington
202-358-5241

Michael Mewhinney
Ames Research Center, Moffett Field, Calif.
650-604-3937

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WISE Captures the Unicorn's Rose

A new image taken by WISE shows the Rosette nebula located within the constellation Monoceros, or the Unicorn. Image credit: NASA/JPL-Caltech/UCLA . Full image and caption

Unicorns and roses are usually the stuff of fairy tales, but a new cosmic image taken by NASA's Wide-field Infrared Explorer (WISE) shows the Rosette nebula located within the constellation Monoceros, or the Unicorn.

This flower-shaped nebula, also known by the less romantic name NGC 2237, is a huge star-forming cloud of dust and gas in our Milky Way galaxy. Estimates of the nebula's distance vary from 4,500 to 5,000 light-years away.

At the center of the flower is a cluster of young stars called NGC 2244. The most massive stars produce huge amounts of ultraviolet radiation, and blow strong winds that erode away the nearby gas and dust, creating a large, central hole. The radiation also strips electrons from the surrounding hydrogen gas, ionizing it and creating what astronomers call an HII region.

Although the Rosette nebula is too faint to see with the naked eye, NGC 2244 is beloved by amateur astronomers because it is visible through a small telescope or good pair of binoculars. The English astronomer John Flamsteed discovered the star cluster NGC 2244 with a telescope around 1690, but the nebula itself was not identified until John Herschel (son of William Herschel, discoverer of infrared light) observed it almost 150 years later.

The streak seen at lower left is the trail of a satellite, captured as WISE snapped the multiple frames that make up this view.

This image is a four-color composite created by all four of WISE's infrared detectors. Color is representational: blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is dominated by light from stars. Green and red represent light at 12 and 22 microns, which is mostly light from warm dust.

JPL manages the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu.

Whitney Clavin (818) 354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

whitney.clavin@jpl.nasa.gov

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Wednesday, August 25, 2010

New International Study Shows Some Asteroids Live in Own 'Little Worlds'

Illustration of a binary asteroid. Courtesy ESO/L. Calcada

While the common perception of asteroids is that they are giant rocks lumbering about in orbit, a new study shows they actually are constantly changing "little worlds" that can give birth to smaller asteroids that split off to start their own lives as they circle around the sun.

Astronomers have known that small asteroids get "spun up" to fast rotation rates by sunlight falling on them, much like propellers in the wind. The new results show when asteroids spin fast enough, they can undergo "rotational fission," splitting into two pieces which then begin orbiting each other. Such "binary asteroids" are fairly common in the solar system.

The new study, led by Petr Pravec of the Astronomical Institute in the Czech Republic and involving the University of Colorado at Boulder and 15 other institutions around the world, shows that many of these binary asteroids do not remain bound to each other but escape, forming two asteroids in orbit around the sun when there previously was just one. The study appears in the Aug. 26 issue of Nature.

The researchers studied 35 so-called "asteroid pairs," separate asteroids in orbit around the sun that have come close to each other at some point in the past million years -- usually within a few miles, or kilometers -- at very low relative speeds. They measured the relative brightness of each asteroid pair, which correlates to its size, and determined the spin rates of the asteroid pairs using a technique known as photometry.

"It was clear to us then that just computing orbits of the paired asteroids was not sufficient to understand their origin," said Pravec. "We had to study the properties of the bodies. We used photometric techniques that allowed us to determine their rotation rates and study their relative sizes."

The research team showed that all of the asteroid pairs in the study had a specific relationship between the larger and smaller members, with the smallest one always less than 60 percent of the size of its companion asteroid. The measurement fits precisely with a theory developed in 2007 by study co-author and CU-Boulder aerospace engineering sciences Professor Daniel Scheeres.

Scheeres' theory predicts that if a binary asteroid forms by rotational fission, the two can only escape from each other if the smaller one is less than 60 percent of the size of the larger asteroid. When one of the asteroids in the pair is small enough, it can "make a break for it" and escape the orbital dance, essentially moving away to start its own "asteroid family," he said. During rotational fission, the asteroids separate gently from each other at relatively low velocities.

"This is perhaps the clearest observational evidence that asteroids aren't just large rocks in orbit about the sun that keep the same shape over time," said Scheeres. "Instead, they are little worlds that may be constantly changing as they grow older, sometimes giving birth to smaller asteroids that then start their own life in orbit around the sun."

While asteroid pairs were first discovered in 2008 by paper co-author David Vokrouhlicky of Charles University in Prague, their formation process remained a mystery prior to the new Nature study.

When the binary asteroid forms, the orbit of the two asteroids around each other is initially chaotic, Scheeres said. "The smaller guy steals rotational energy from the bigger guy, causing the bigger guy to rotate more slowly and the size of the orbit of the two bodies to expand. If the second asteroid is small enough, there is enough excess energy for the pair to escape from each other and go into their own orbits around the sun."

Several telescopes around the world were used for the study, with the most thorough observations made with the 1-meter telescope at Wise Observatory in the Negev Desert in Israel and the Danish 1.54-meter telescope at La Silla, Chile. "This study makes the clear connection between asteroids spinning up and breaking into pieces, showing that asteroids are not static, monolithic bodies," said Vokrouhlicky.

The asteroids that populate the solar system are primarily concentrated in the main asteroid belt between Mars and Jupiter some 200 million miles from the sun, but extend all the way down into the inner solar system, which are known as the near-Earth asteroids. There are likely about a million asteroids larger than 0.6 miles, or 1 kilometer, in diameter orbiting the sun. Last month, NASA's WISE spacecraft spotted 25,000 never-before-seen asteroids in just six months.

Astronomers believe most asteroids are not solid chunks of rock, but rather piles of debris that come in shapes ranging from snowmen and dog bones to potatoes and bananas, with each asteroid essentially glued together by gravitational forces.

"Sunlight striking an asteroid less than 10 kilometers across can change its rotation over millions of years, a slow motion version of how a windmill reacts to the wind," said Scheeres, who has studied asteroids for the past decade. "This causes the smaller asteroid to rotate more rapidly until it can undergo rotational fission. It's not hard for these asteroid pairs to be pushed over the edge."

CU-Boulder doctoral student Seth Jacobson of CU-Boulder's astrophysical and planetary sciences department, a co-author on the Nature paper, said the most surprising part of the study was showing that sunlight played the key role in "birthing" asteroids. "There was a time when most astronomers referred to asteroids as vermin," said Jacobson. "But the more we learn about them, the more exciting they are. They are not just big chunks of rock, but have the dynamic ability to evolve."

The asteroids in the study ranged from about 1 kilometer to about 10 kilometers or about 0.6 miles to 6 miles in diameter, said Jacobson. He said one of the biggest questions is what lies beneath the surfaces of asteroids. "This is something we just don't know yet," he said.

Asteroids have become a hot topic, said Scheeres. The Japanese spacecraft Hayabusa made two landings on the asteroid Itokawa in 2005 before its recent return to Earth -- the first spacecraft ever to visit an asteroid and return to the planet. Scientists are hopeful the spacecraft recovered at least some particles from the asteroid, which may give them more information about the origin and evolution of the solar system roughly 4.6 billion years ago.

President Barack Obama this year announced his vision for planetary exploration that involves skipping future manned moon landings in favor of sending astronauts to a near-Earth asteroid in the next two decades. Obama and others see a successful manned asteroid landing as a stepping stone to eventually landing humans on Mars.

"Asteroids are important to understanding life on Earth," said Pravec. He pointed to the Chicxulub asteroid believed to have plowed into the Yucatan Peninsula 65 million years ago and caused dinosaurs to go extinct, essentially resetting the evolutionary clock on Earth. Some asteroids have even been found to contain amino acids -- the building blocks of life -- causing some scientists to speculate that life on Earth could have come from asteroids pelting the planet.

Other co-authors of the study are from institutions in North Carolina, California, Massachusetts, Chile, Israel, Slovakia, the Ukraine, Spain and France.

Contact

Daniel Scheeres, CU-Boulder, 303-492-7420

Daniel.Scheeres@colorado.edu

Seth Jacobson, CU-Boulder
Seth.Jacobson@colorado.edu

David Vokrouhlicky, Charles University, Prague, +420-2-21912574
vokrouhl@cesnet.cz

Jim Scott, 303-492-3114
Jim.Scott@colorado.edu

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"Caution: Merging Galaxies"


Using supercomputers to simulate ancient galaxy mergers, an Ohio State researcher has made a discovery: Intergalactic traffic collisions some 13 billion years ago gave rise to the universe’s first super-massive black holes.

Intergalactic traffic collisions some 13 billion years ago gave rise to the universe's first super-massive black holes – and one of the Milky Way’s nearest neighbors.

That's what a postdoctoral researcher at Ohio State's Center for Cosmology and Astro-Particle Physics discovered, when he simulated ancient galaxy mergers on supercomputers.

The discovery fills in a missing chapter of our universe's early history, and could help write the next chapter--in which scientists better understand how gravity and dark matter formed the universe as we know it.

In the journal Nature, Stelios Kazantzidis and colleagues describe computer simulations in which they modeled the evolution of galaxies and black holes during the first few billion years after the Big Bang.

Our universe is thought to be 14 billion years old. Other astronomers recently determined that big galaxies formed much earlier in the universe’s history than previously thought--within the first 1 billion years, Kazantzidis explained.

These new computer simulations show that the first-ever super-massive black holes were likely born when those early galaxies collided and merged together.

"Our results add a new milestone to the important realization of how structure forms in the universe," he said.

The galaxies that formed those first super-massive black holes are still around, Kazantzidis added.

"One of them is likely our neighbor in the Virgo Cluster, the elliptical galaxy M87," he said. "The galaxies we saw in our simulation would be the biggest galaxies known today, about 100 times the size of the Milky Way. M87 fits that description."

He and his cohorts also hope that their work will aid astronomers who are searching the skies for direct evidence of Einstein’s theory of general relativity: gravitational waves.

According to general relativity, any ancient galaxy mergers would have created massive gravitational waves--ripples in the space-time continuum--the remnants of which should still be visible today.

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The Ring Nebula

This image of the Ring Nebula or Messier 57 was obtained using the Wide Field Camera on the Isaac Newton Telescope. It is a three-colour composite made from data collected using filters to isolate the light emitted by hydrogen alpha (H-alpha), doubly ionised oxygen (OIII) and ionised sulfur (SII) atoms, and coded in the image as red, green and blue respectively. Credit: D. López (IAC) [ JPEG | TIFF | PDF (with text) ]

Messier 57 (M57) planetary nebula, also known as the "Ring Nebula", is often regarded as the prototype of a planetary nebula. Observations have confirmed that it is, most probably, actually a ring (torus) of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal) shell.

This image was obtained and processed by members of the IAC astrophotography group (A. Oscoz, D. López, P. Rodríguez-Gil and L. Chinarro).

More information:
M57 - IAC Astrophoto June 2009
IAC Astronomical Picture of the Month

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Evidence for Galaxy Interactions in Powerful Radio Galaxies

Figure 1. Example of the detection of tidal tails (labelled as T1, T2, and T3), a bridge, and dust in the interacting system between the PRG PKS 0347+05 (center) and a quasar. The dark halos around unresolved objects, like the quasar, in this and other figures are a consequence of the unsharp-mask processing of the image.

Figure 2. The radio galaxy PKS 1355-41 shows a shell and a bright tail toward the lower right of the bright nucleus.

Figure 3. The radio galaxy PKS 0349-27, is linked to two nearby galaxies (labelled as Gal 1 and Gal2). Tidal tails (T1 and T2) are also detected.

Testing the idea that the powerful radio galaxies (PRGs) are triggered in galaxy interactions, Cristina Ramos Almeida, Clive Tadhunter (University of Sheffield, UK), and collaborators obtained deep imaging data using the Gemini Multi-Object Spectrograph (GMOS) at the Gemini South telescope to study the morphologies of a complete sample of 46 intermediate redshift (0.05<z<0.7) PRGs. In what represents the first systematic imaging study of a major sample of radio galaxies using an 8-meter-class telescope, the team searched for signs of nearby companions in the 2Jy southern radio galaxy sample to look for secondary nuclei, shells, and extended low surface brightness features such as tidal tails and bridges.

The observations show that 78-85% of this complete sample of PRGs present peculiar morphologies at relatively high levels of surface brightness (μv = 23.6 mag/arcsec2). This fraction of distorted morphologies is much higher than for radio quiet ellipticals at similar sample brightness level, implying that galaxy interactions are likely to play a key role in the triggering of AGN/radio activity. The morphological peculiarities of the galaxies include tails, fans, bridges, shells, dust lanes, irregular features, amorphous haloes, and multiple nuclei (Figures 1-3), which are likely the result of the merger or close encounter of galaxies in pairs or groups. For more than one-third of the sample, the morphologies are consistent with the galaxies being observed after the first peri-center passage but before the final coalescence of the merging nuclei. If radio galaxies are indeed triggered in galaxy mergers, it does not happen at a unique phase of the merger. Moreover, since we do not know the relative velocities of the galaxies, it is not possible to rule out the idea that the activity in some galaxies has been triggered in galaxy encounters that will not eventually lead to a merger.

Dividing the sample on the basis of the optical spectra, the team finds that only 27% of the galaxies with weak optical lines show clear evidence for interactions, in contrast to 94% of the strong-line radio galaxies (SLRGs) that appear to be interacting. This result is consistent with the idea that Bondi accretion of hot gas from the X-ray corona fuels many WLRGs. However, the evidence for interactions and dust features in a fraction of them indicates that cold gas accretion cannot always be ruled out.

The complete results will appear in Montly Notices of the Royal Astronomical Society, and a preprint is currently available on astro-ph.

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Tuesday, August 24, 2010

Richest Planetary System Discovered

The planetary system around the Sun-like star HD 10180
(artist’s impression)

Wide-field view of the sky around the star HD 10180

Close-up view of the sky around the star HD 10180

ESOcast 20: Richest planetary system discovered

Animation of the planetary system around Sun-like star HD 10180
(artist’s impression)

Animation of the planetary system around Sun-like star HD 10180
(artist’s impression)

Animation of the planetary system around Sun-like star HD 10180
(artist’s impression)

Animation of the planetary system around Sun-like star HD 10180
(artist’s impression)

Zooming in on the Sun-like star HD 10180

The radial velocity method for finding exoplanets

Up to seven planets orbiting a Sun-like star

Astronomers using ESO’s world-leading HARPS instrument have discovered a planetary system containing at least five planets, orbiting the Sun-like star HD 10180. The researchers also have tantalising evidence that two other planets may be present, one of which would have the lowest mass ever found. This would make the system similar to our Solar System in terms of the number of planets (seven as compared to the Solar System’s eight planets). Furthermore, the team also found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our Solar System.

“We have found what is most likely the system with the most planets yet discovered,” says Christophe Lovis, lead author of the paper reporting the result. “This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system.”

The team of astronomers used the HARPS spectrograph, attached to ESO’s 3.6-metre telescope at La Silla, Chile, for a six-year-long study of the Sun-like star HD 10180, located 127 light-years away in the southern constellation of Hydrus (the Male Water Snake). HARPS is an instrument with unrivalled measurement stability and great precision and is the world’s most successful exoplanet hunter.

Thanks to the 190 individual HARPS measurements, the astronomers detected the tiny back and forth motions of the star caused by the complex gravitational attractions from five or more planets. The five strongest signals correspond to planets with Neptune-like masses — between 13 and 25 Earth masses [1] — which orbit the star with periods ranging from about 6 to 600 days. These planets are located between 0.06 and 1.4 times the Earth–Sun distance from their central star.

“We also have good reasons to believe that two other planets are present,” says Lovis. One would be a Saturn-like planet (with a minimum mass of 65 Earth masses) orbiting in 2200 days. The other would be the least massive exoplanet ever discovered, with a mass of about 1.4 times that of the Earth. It is very close to its host star, at just 2 percent of the Earth–Sun distance. One “year” on this planet would last only 1.18 Earth-days.

“This object causes a wobble of its star of only about 3 km/hour— slower than walking speed — and this motion is very hard to measure,” says team member Damien Ségransan. If confirmed, this object would be another example of a hot rocky planet, similar to Corot-7b (eso0933).

The newly discovered system of planets around HD 10180 is unique in several respects. First of all, with at least five Neptune-like planets lying within a distance equivalent to the orbit of Mars, this system is more populated than our Solar System in its inner region, and has many more massive planets there [2]. Furthermore, the system probably has no Jupiter-like gas giant. In addition, all the planets seem to have almost circular orbits.

So far, astronomers know of fifteen systems with at least three planets. The last record-holder was 55 Cancri, which contains five planets, two of them being giant planets. “Systems of low-mass planets like the one around HD 10180 appear to be quite common, but their formation history remains a puzzle,” says Lovis.

Using the new discovery as well as data for other planetary systems, the astronomers found an equivalent of the Titius–Bode law that exists in our Solar System: the distances of the planets from their star seem to follow a regular pattern [3]. “This could be a signature of the formation process of these planetary systems,” says team member Michel Mayor.

Another important result found by the astronomers while studying these systems is that there is a relationship between the mass of a planetary system and the mass and chemical content of its host star. All very massive planetary systems are found around massive and metal-rich stars, while the four lowest-mass systems are found around lower-mass and metal-poor stars [4]. Such properties confirm current theoretical models.

The discovery is announced today at the international colloquium “Detection and dynamics of transiting exoplanets”, at the Observatoire de Haute-Provence, France.

Notes

[1] Using the radial velocity method, astronomers can only estimate a minimum mass for a planet as the mass estimate also depends on the tilt of the orbital plane relative to the line of sight, which is unknown. From a statistical point of view, this minimum mass is however often close to the real mass of the planet.

[2] On average the planets in the inner region of the HD 10180 system have 20 times the mass of the Earth, whereas the inner planets in our own Solar System (Mercury, Venus, Earth and Mars) have an average mass of half that of the Earth.

[3] The Titius–Bode law states that the distances of the planets from the Sun follow a simple pattern. For the outer planets, each planet is predicted to be roughly twice as far away from the Sun as the previous object. The hypothesis correctly predicted the orbits of Ceres and Uranus, but failed as a predictor of Neptune’s orbit.

[4] According to the definition used in astronomy, “metals” are all the elements other than hydrogen and helium. Such metals, except for a very few minor light chemical elements, have all been created by the various generations of stars. Rocky planets are made of “metals”.

More information

This research was presented in a paper submitted to Astronomy and Astrophysics (“The HARPS search for southern extra-solar planets. XXVII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems” by C. Lovis et al.).

The team is composed of C. Lovis, D. Ségransan, M. Mayor, S. Udry, F. Pepe, and D. Queloz (Observatoire de Genève, Université de Genève, Switzerland), W. Benz (Universität Bern, Switzerland), F. Bouchy (Institut d’Astrophysique de Paris, France), C. Mordasini (Max-Planck-Institut für Astronomie, Heidelberg, Germany), N. C. Santos (Universidade do Porto, Portugal), J. Laskar (Observatoire de Paris, France), A. Correia (Universidade de Aveiro, Portugal), and J.-L. Bertaux (Université Versailles Saint-Quentin, France) and G. Lo Curto (ESO).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links
Research paper
More info: Exoplanet Press Kit

Contacts

Christophe Lovis
Observatoire de l’Université de Genève
Switzerland
Cell: +41 787 280 354
Email:
christophe.lovis@unige.ch

Damien Ségransan
Observatoire de l’Université de Genève
Switzerland
Tel: +41 223 792 479
Email:
damien.segransan@unige.ch

Francesco Pepe
Observatoire de l’Université de Genève
Switzerland
Tel: +41 223 792 396
Email:
francesco.pepe@unige.ch

Richard Hook
La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Email:
rhook@eso.org

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Monday, August 23, 2010

Pulverized Planet Dust Might Lie Around Double Stars

This artist's concept illustrates an imminent planetary collision around a pair of double stars. NASA's Spitzer Space Telescope found evidence that such collisions could be common around a certain type of tight double, or binary, star system, referred to as RS Canum Venaticorums or RS CVns for short. The stars are similar to the sun in age and mass, but they orbit tightly around each other. With time, they are thought to get closer and closer, until their gravitational influences change, throwing the orbits of planetary bodies circling around them out of whack and leading to collisions. Spitzer's infrared vision spotted dusty evidence for such collisions around three tight star pairs.Credit: NASA/JPL-Caltech. High Resolution Image (jpg)

This artist's concept illustrates a tight pair of stars and a surrounding disk of dust -- most likely the shattered remains of planetary smashups. Using NASA's Spitzer Space Telescope, the scientists found dusty evidence for such collisions around three sets of stellar twins (a class of stars called RS Canum Venaticorums or RS CVns for short). The stars, which are similar to our sun in mass and age, orbit very closely around each other. They are separated by just one-fiftieth of the Earth-sun distance. As time goes by, the stars get closer and closer, and this causes the gravitational harmony in the systems to go out of whack. Comets and any planets orbiting around the stars could jostle about and collide. Credit: NASA/JPL-Caltech. High Resolution Image (jpg)

Cambridge, MA - Tight double-star systems might not be the best places for life to spring up, according to a new study using data from NASA's Spitzer Space Telescope. The infrared observatory spotted a surprisingly large amount of dust around three mature, close-orbiting star pairs. Where did the dust come from? Astronomers say it might be the aftermath of tremendous planetary collisions.

"This is real-life science fiction," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. "Our data tell us that planets in these systems might not be so lucky -- collisions could be common. It's theoretically possible that habitable planets could exist around these types of stars, so if there happened to be any life there, it could be doomed."

Drake is the principal investigator of the research, published in the Aug. 19 issue of the Astrophysical Journal Letters.

The particular class of binary, or double, stars in the study are about as snug as stars get. Named RS Canum Venaticorums, or RS CVns for short, they are separated by only about two million miles (3.2 million kilometers), or one-fiftieth the distance between Earth and our sun. The stellar pairs orbit around each other every few days, with one face on each star perpetually locked and pointed toward the other.

The close-knit stars are similar to the sun in size and are probably about a billion to a few billion years old. But these stars spin much faster, and, as a result, have powerful magnetic fields and giant, dark spots. The magnetic activity drives strong stellar winds -- gale-force versions of the solar wind -- that slow the stars down, pulling the twirling duos closer over time. And this is where the planetary chaos might begin.

As the stars cozy up to each other, their gravitational influences change, and this could cause disturbances to planetary bodies orbiting around both stars. Comets and any planets that might exist in the systems would start jostling about and banging into each other, sometimes in powerful collisions. This includes planets that could theoretically be circling in the double stars' habitable zone -- a region where temperatures would allow liquid water to exist. Though no habitable planets have been discovered around any stars beyond our sun at this point in time, tight double-star systems are known to host planets; for example, one system not in the study, called HW Vir, has two gas-giant planets.

"These kinds of systems paint a picture of the late stages in the lives of planetary systems," said Marc Kuchner, a co-author from NASA Goddard Space Flight Center in Greenbelt, Md. "And it's a future that's messy and violent."

Spitzer spotted the infrared glow of hot dusty disks, about the temperature of molten lava, around three such tight binary systems. One of the systems was originally flagged as having a suspicious excess of infrared light in 1983 by the Infrared Astronomical Satellite. In addition, researchers using Spitzer recently found a warm disk of debris around another star that turned out to be a tight binary system.

The team says that dust normally would have dissipated and blown away from the stars by this mature stage in their lives. They conclude that something -- most likely planetary collisions -- must therefore be kicking up the fresh dust. In addition, because dusty disks now have been found around four, older binary systems, the scientists know that the observations are not a fluke. Something chaotic is very likely going on.

If any life forms did exist in these star systems, and they could look up at the sky, they would have quite a view. Marco Matranga, first author of the paper, from the Harvard-Smithsonian Center for Astrophysics and now a visiting astronomer at the Palermo Astronomical Observatory in Sicily, said, "The skies there would have two huge suns, like the ones above the planet Tatooine in 'Star Wars.'"

Other authors include V.L. Kashyap of the Harvard-Smithsonian Center for Astrophysics; and Massimo Marengo of Iowa State University, Ames.

The Spitzer observations were made before it ran out of its liquid coolant in May 2009, officially beginning its warm mission.

This press release is being issued jointly with the Jet Propulsion Laboratory, Pasadena, Calif.

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.Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462

daguilar@cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463

cpulliam@cfa.harvard.edu

Whitney Clavin
Jet Propulsion Laboratory
818-354-4673

whitney.clavin@jpl.nasa.gov

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Weighing the Planets - from Mercury to Saturn

Pulsar timing observations allow a new way to estimate planet masses

An international research team led by David Champion, now at Max Planck Institute for Radio Astronomy in Bonn, with researchers from Australia, Germany, the U.S., UK and Canada has come up with a new way to weigh the planets in our Solar System, using radio signals from pulsars. Data from a set of four pulsars have been used to weigh Mercury, Venus, Mars, Jupiter and Saturn with their moons and rings.
The new measurement technique is sensitive to just 0.003% of the mass of the Earth, and one ten-millionth of Jupiter's mass (corresponding to a mass difference of two hundred thousand million million tonnes). The results are described in an article for the "Astrophysical Journal", which is publicly accessible via preprint-server.

Figure 1: Planets in the solar system with their masses determined by means of pulsar timing observations. Image: David Champion

Until now, astronomers have weighed planets by measuring the orbits of their moons or of spacecraft flying past them. That's because mass creates gravity, and a planet's gravitational pull determines the orbit of anything that goes around it - both the size of the orbit and how long it takes to complete. The new method is based on corrections astronomers make to signals from pulsars, small spinning stars that deliver regular "blips" of radio waves. Measurements of planet masses made this new way could feed into data needed for future space missions.

"This is first time anyone has weighed entire planetary systems-planets with their moons and rings," says team leader Dr. David Champion of the Max Planck Institute for Radio Astronomy. "In addition, we can provide an independent check on previous results, which is great for planetary science."

The Earth is travelling around the Sun, and this movement affects exactly when pulsar signals arrive here. To remove this effect, astronomers calculate when the pulses would have arrived at the Solar System's centre of mass, or barycentre, the rotation centre for all the planets. Because the arrangement of the planets around the Sun changes with time, the barycentre moves around too (relative to the sun).

To work out its position, astronomers use both a table with the positions of the planets in the sky (called an ephemeris), and the values for their masses that have already been measured. If these figures are slightly wrong, and the position of the barycentre is slightly wrong, then a regular, repeating pattern of timing errors appears in the pulsar data. "For instance, if the mass of Jupiter and its moons is wrong, we see a pattern of timing errors that repeats over 12 years, the time Jupiter takes to orbit the Sun," says Dr. Dick Manchester of CSIRO Astronomy and Space Science. But if the mass of Jupiter and its moons is corrected, the timing errors disappear. This is the feedback process that the astronomers have used to determine the planets' masses.

Data from a set of four pulsars have been used to weigh Mercury, Venus, Mars, Jupiter and Saturn with their moons and rings. Most of these data were recorded by CSIRO's Parkes radio telescope in eastern Australia, with data contributed by the Effelsberg telescope in Germany and the Arecibo telescope in Puerto Rico. The masses were consistent with those measured by spacecraft. The mass of the Jovian system (Jupiter and its moons), 9.547921(2) x 10-4 times the mass of the Sun, is significantly more accurate than the mass determined from the Pioneer and Voyager spacecraft, and consistent with, but less accurate than, the value from the Galileo spacecraft.

The new measurement technique is sensitive to a mass difference of two hundred thousand million million tonnes-just 0.003% of the mass of the Earth, and one ten-millionth of Jupiter's mass. In the short term, spacecraft will continue to make the most accurate measurements for individual planets, but the pulsar technique will be the best for planets not being visited by spacecraft, and for measuring the combined masses of planets and their moons. Repeating the measurements would improve the values even more. If astronomers observed a set of 20 pulsars over seven years they'd weigh Jupiter more accurately than spacecraft have. Doing the same for Saturn would take 13 years.

"Astronomers need this accurate timing because they're using pulsars to hunt for gravitational waves predicted by Einstein's general theory of relativity", says Prof. Michael Kramer, head of the "Fundamental Physics in Radio Astronomy" research group at Max Planck Institute for Radio Astronomy. "Finding these waves depends on spotting minute changes in the timing of pulsar signals, and so all other sources of timing error must be accounted for, including the traces of solar system planets."

Figure 2: Radio telescopes utilized for the pulsar timing observations: Parkes 64 m telescope (left), Effelsberg 100 m telescope (centre), Arecibo 305 m telescope (right). Images: CASS, MPIfR, NAIC

Original Paper:

Measuring the mass of solar-system planets using pulsar timing , D.J. Champion, G.B. Hobbs, R.N. Manchester, R.T. Edwards, D.C. Backer, M. Bailes, N.D.R. Bhat, S. Burke-Spolaor, W. Coles, P.B. Demorest, R.D. Ferdman, W.M. Folkner, A.W. Hotan, M. Kramer, A.N. Lommen, D.J. Nice, M.B. Purver, J.M. Sarkissian, I.H. Stairs, W. van Straten, J.P.W. Verbiest, D.R.B. Yardley, 2010, Astrophysical Journal (astro-ph).


Further Information:

Max-Planck-Institute für Radioastronomie (MPIfR).

Fundamental Physics in Radio Astronomy , Research group at MPIfR

Interview with David Champion (zip file; Video Credit: CSIRO)

CSIRO Astronomy and Space Science (CASS)

Australia Telescope National Facility (ATNF)

Arecibo Observatory , National Astronomy and Ionosphere Center (NAIC), Puerto Rico

Jodrell Bank Centre for Astrophysics

European Pulsar Timing Array (EPTA)


Parallel and Earlier Press Releases:

A new way to weigh planets, CSIRO Media Release 10/114 - 23 August 2010.

Astronomers making good time, PRI (MPIfR) 06/2010 (5), June 24, 2010.


Local Contact:

Dr. David Champion,
Max-Planck-Institut für Radioastronomie, Bonn.
UK mobile: +44 7831 710 456
DE mobile: +49 151 4003 9782
E-mail:
davidjohnchampion@gmail.com

Dr. Norbert Wex,
Max-Planck-Institut für Radioastronomie, Bonn.
Fon: +49-228-525-503
E-mail:
wex@mpifr-bonn.mpg.de

Dr. Norbert Junkes,
Public Outreach,
Max-Planck-Institut für Radioastronomie, Bonn.
Fon: +49-228-525-399
E-mail:
njunkes@mpifr-bonn.mpg.de

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Friday, August 20, 2010

Galactic Plane - Aquila

Image Credit: ESA / SPIRE / PACS / Hi-GAL

This image combines data from PACS and SPIRE to form a three-colour image. PACS images at 70 microns (blue), 160microns (green) are combined with the SPIRE 250 microns channel (red). Cooler material is shown in red, while warmer material is blue - but all just 10-50 degreen above absolute zero. This image is taken in constellation of Aquila and shows the entire assembly line of newborn stars. The diffuse glow reveals the widespread cold reservoir of raw material which our Galaxy has in stock for the production of new stars.

Two bright star forming regions are seen on the left and centre, called W43 and G29.9 respectively. Below W43, a cavity can be seen in the interstellar medium. The strong winds from the stars forming in the dense clump are pushing the material out, blowing the bobble.

This image is taken as part of a project called "Hi-GAL", which aims to image a strip across the plane of our Galaxy towards its central regions. This is a section 30 degrees away from the centre of our Galaxy.

Fast Facts For Galactic Plane - Aquila

Object Name: Galactic Plane
Type of Object: Interstellar Medium
Image Scale: The image is 2 degrees across
RA: -78.4
DEC: 2.61
Constellation: Aquila the Eagle
Instrument: SPIRE and PACS
Observation Date/Time: Wed, 28/04/2010 (All day)
Wavelengths: 70, 160, 250 microns
Date of Release: 06/05/2010
Key Programme: Hi-GAL

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Thursday, August 19, 2010

New Herbig-Haro Jets in Orion




Figure 1: Suprime-Cam image of Lynds 1641, a molecular cloud to the south of Orion Nebula. It reveals many jet features from the new-born stars, depicted in three samples above.

A research team using the Subaru Prime Focus Camera (Suprime-Cam) has obtained some of the deepest and highest resolution images ever taken of the large star-forming molecular cloud Lynds 1641, located just south of the Orion Nebula. Many bright Herbig-Haro flows occupy this part of the sky. Emissions from Herbig-Haro objects are caused by powerful shock waves that occur when supersonic outflows from newborn stars ram through the interstellar medium. Such outflow phenomena usually occur during the very early stages of star formation, when newborn stars are still deeply embedded in their placental materials of gas and dust. The discovery of 11 new jets of gas, fainter than most of those known in the region, required the combination of Suprime-Cam's large field-of-view with the powerful light-gathering capability of the Subaru Telescope's 8 m mirror.

It was surprising that all of the newly observed jets emanate from visible stars, which have already made their way out of the cocoon from which they were born. Researchers speculate that the newly discovered jets may derive from one of two sources. They may represent the final vestiges of the outflow phenomena. Or, the jets may be triggered by disturbances in remnant circumstellar disks, which might be perturbed by the close passage of a companion star in a binary system.

The results of this research will published in the Astrophysical Journal. Detailed studies of the jets and their driving sources are planned to understand the nature of these unexpected outflows.

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First Use of Cosmic Lens to Probe Dark Energy

Dark Matter Map in Galaxy Cluster Abell 1689
Credit: NASA, ESA, E. Jullo (Jet Propulsion Laboratory),
P. Natarajan (Yale University),
and J.-P. Kneib (Laboratoire d'Astrophysique de Marseille, CNRS, France)

Astronomers have devised a new method for measuring perhaps the greatest puzzle of our universe — dark energy. This mysterious force, discovered in 1998, is pushing our universe apart at ever-increasing speeds.

For the first time, astronomers using NASA's Hubble Space Telescope were able to take advantage of a giant magnifying lens in space — a massive cluster of galaxies — to narrow in on the nature of dark energy. Their calculations, when combined with data from other methods, significantly increase the accuracy of dark energy measurements. This may eventually lead to an explanation of what the elusive phenomenon really is.

"We have to tackle the dark energy problem from all sides," said Eric Jullo, an astronomer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It's important to have several methods, and now we've got a new, very powerful one." Jullo is lead author of a paper on the findings appearing in the Aug. 20 issue of the journal Science.

Scientists aren't clear about what dark energy is, but they do know that it makes up a large chunk of our universe, about 72 percent. Another chunk, about 24 percent, is thought to be dark matter, also mysterious in nature but easier to study than dark energy because of its gravitational influence on matter that we can see. The rest of the universe, a mere 4 percent, is the stuff that makes up people, planets, stars, and everything made up of atoms.

In their new study, the science team used images from Hubble to examine a massive cluster of galaxies, named Abell 1689, which acts as a magnifying, or gravitational, lens. The gravity of the cluster causes galaxies behind it to be imaged multiple times into distorted shapes, sort of like a fun-house mirror reflection that warps your face.

Using these distorted images, the scientists were able to figure out how light from the more distant, background galaxies had been bent by the cluster — a characteristic that depends on the nature of dark energy. Their method also depends on precise ground-based measurements of the distance and speed at which the background galaxies are traveling away from us. The team used these data to quantify the strength of the dark energy that is causing our universe to accelerate.

"What I like about our new method is that it's very visual," said Jullo, "You can literally see gravitation and dark energy bend the images of the background galaxies into arcs."

According to the scientists, their method required multiple, meticulous steps. They spent the last several years developing specialized mathematical models and precise maps of the matter — both dark and "normal" — constituting the Abell 1689 cluster.

"We can now apply our technique to other gravitational lenses," said co-author Priya Natarajan, a cosmologist at Yale University, New Haven, Conn. "We're exploiting a beautiful phenomenon in nature to learn more about the role that dark energy plays in our universe."

Other authors of the paper include Jean-Paul Kneib and Carlo Schimd of the Laboratoire d'Astrophysique de Marseille, France; Anson D'Aloisio of Yale University; Marceau Limousin of Laboratoire d'Astrophysique de Marseille, France, and University of Copenhagen, Denmark; and Johan Richard of Durham University, United Kingdom.

CONTACT

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514

villard@stsci.edu

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-4673

whitney.clavin@jpl.nasa.gov

Oli Usher
ESO, Hubble-Europe Information Center, Garching, Germany
011-49-89-3200-6855

ousher@eso.org

Eric Jullo
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-5511

eric.jullo@jpl.nasa.gov

Priyamvada Natarajan
Yale University, New Haven, Conn.
617-945-0542

priyamvada.natarajan@yale.edu

Jean-Paul Kneib
Laboratoire d'Astrophysique de Marseille, CNRS, France
011-33-685-988-265

jean-paul.kneib@oamp.fr

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