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Archive for April, 2013

Detection Of Two New Exoplanets With Kepler, SOPHIE And HARPS-N


An international team of astronomers, including Alexandre Santerne of the EXOEarths team, identified and characterized two new exoplanets, thanks to combined observations from the Kepler space telescope, plus SOPHIE and HARPS-N spectrographs.

These planets, named KOI-200 b and KOI-889 b are among the first detected with the new high-accuracy spectrograph HARPS-N, the northern hemisphere counterpart of the most prolific exoplanet hunter, HARPS (ESO). CAUP researcher Alexandre Santerne commented: “The SOPHIE spectrograph was already playing an important role in the characterization of Kepler planets by unveiling the true nature of the candidates and measuring the mass of giant planets. With the new HARPS-N spectrograph, with an even better accuracy, we expect to characterize much smaller exoplanets, hopefully down to the size of the Earth.”

The new planets have about the size of Jupiter, but eccentric orbits with periods of less than 10 days. These new results help to further understand the evolution of orbits of these planets located very close to their star, known as “hot Jupiters”

Full Story: http://www.astro.up.pt/exoearths/news/130429twonewexoplanets.html

NASA Probe Observes Meteors Colliding With Saturn’s Rings


Image Credit: NASA/JPL-Caltech/Space Science Institute/Cornell

Image Credit: NASA/JPL-Caltech/Space Science Institute/Cornell

NASA’s Cassini spacecraft has provided the first direct evidence of small meteoroids breaking into streams of rubble and crashing into Saturn’s rings.

These observations make Saturn’s rings the only location besides Earth, the moon and Jupiter where scientists and amateur astronomers have been able to observe impacts as they occur. Studying the impact rate of meteoroids from outside the Saturnian system helps scientists understand how different planet systems in our solar system formed.

The solar system is full of small, speeding objects. These objects frequently pummel planetary bodies. The meteoroids at Saturn are estimated to range from about one-half inch to several yards (1 centimeter to several meters) in size. It took scientists years to distinguish tracks left by nine meteoroids in 2005, 2009 and 2012.

Results from Cassini have already shown Saturn’s rings act as very effective detectors of many kinds of surrounding phenomena, including the interior structure of the planet and the orbits of its moons. For example, a subtle but extensive corrugation that ripples 12,000 miles (19,000 kilometers) across the innermost rings tells of a very large meteoroid impact in 1983.

Full Story: http://www.jpl.nasa.gov/news/news.php?release=2013-147

Einstein’s Gravity Theory Passes Toughest Test Yet


Artist’s impression. Credit: ESO/L. Calçada

Artist’s impression. Credit: ESO/L. Calçada

A strange stellar pair nearly 7,000 light-years from Earth has provided physicists with a unique cosmic laboratory for studying the nature of gravity. The extremely strong gravity of a massive neutron star in orbit with a companion white dwarf star puts competing theories of gravity to a test more stringent than any available before.

Once again, Albert Einstein’s General Theory of Relativity, published in 1915, comes out on top.

At some point, however, scientists expect Einstein’s model to be invalid under extreme conditions. General Relativity, for example, is incompatible with quantum theory. Physicists hope to find an alternate description of gravity that would eliminate that incompatibility.

A newly-discovered pulsar — a spinning neutron star with twice the mass of the Sun — and its white-dwarf companion, orbiting each other once every two and a half hours, has put gravitational theories to the most extreme test yet. Observations of the system, dubbed PSR J0348+0432, produced results consistent with the predictions of General Relativity.

Full Story: http://www.nrao.edu/pr/2013/gravitylab/
Also: http://www.eso.org/public/news/eso1319/

How To Target An Asteroid


Image credit: NASA/JPL-Caltech/UMD

Image credit: NASA/JPL-Caltech/UMD

Like many of his colleagues at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., Shyam Bhaskaran is working a lot with asteroids these days. And also like many of his colleagues, the deep space navigator devotes a great deal of time to crafting, and contemplating, computer-generated 3-D models of these intriguing nomads of the solar system.
But while many of his coworkers are calculating asteroids’ past, present and future locations in the cosmos, zapping them with the world’s most massive radar dishes, or considering how to rendezvous and perhaps even gently nudge an asteroid into lunar orbit, Bhaskaran thinks about how to collide with one.

“If you want to see below the surface of an asteroid, there’s no better way than smacking it hard,” said Bhaskaran. “But it’s not that easy. Hitting an asteroid with a spacecraft traveling at hypervelocity is like shooting an arrow at a target on a speeding race car.

“Most of the hypervelocity impact scenarios that I simulate have spacecraft/asteroid closure rates of around eight miles a second, 30,000 miles per hour [about 48,000 kilometers per hour],” said Bhaskaran.

Full Story: http://www.jpl.nasa.gov/news/news.php?release=2013-138

Using Black Holes To Measure The Universe’s Rate Of Expansion


A few years ago, researchers revealed that the universe is expanding at a much faster rate than originally believed — a discovery that earned a Nobel Prize in 2011. But measuring the rate of this acceleration over large distances is still challenging and problematic, says Prof. Hagai Netzer of Tel Aviv University’s School of Physics and Astronomy.

Now, Prof. Netzer, along with Jian-Min Wang, Pu Du and Chen Hu of the Institute of High Energy Physics of the Chinese Academy of Sciences and Dr. David Valls-Gabaud of the Observatoire de Paris, has developed a method with the potential to measure distances of billions of light years with a high degree of accuracy. The method uses certain types of active black holes that lie at the center of many galaxies. The ability to measure very long distances translates into seeing further into the past of the universe — and being able to estimate its rate of expansion at a very young age.

Published in the journal Physical Review Letters, this system of measurement takes into account the radiation emitted from the material that surrounds black holes before it is absorbed. As material is drawn into a black hole, it heats up and emits a huge amount of radiation, up to a thousand times the energy produced by a large galaxy containing 100 billion stars. For this reason, it can be seen from very far distances, explains Prof. Netzer.

Full Story: http://www.aftau.org/site/News2?page=NewsArticle&id=18463

Astronomer Studies Far-Off Worlds Through ‘Characterization By Proxy’


A University of Washington astronomer is using Earth’s interstellar neighbors to learn the nature of certain stars too far away to be directly measured or observed, and the planets they may host.

“Characterization by proxy” is the technique used by Sarah Ballard, a post-doctoral researcher at the UW, to infer the properties of small, relatively cool stars too distant for measurement, by comparing them to closer stars that now can be directly observed.

Our understanding of the size and temperature of planets depends crucially on the size and temperature of the stars they orbit. Astronomers already have a robust way to discern the physical properties of solar-type stars — those like the sun — by measuring the light they emit at different wavelengths and matching that to synthetically created spectra.

“The challenge is that small stars are incredibly difficult to characterize,” Ballard said. Those theoretical methods don’t work well for what are called M-dwarf stars, lower-mass stars about half the size of the sun and smaller — which is too bad, because such stars make up about three-quarters of the universe.

Full Story: http://www.washington.edu/news/2013/04/25/astronomer-studies-far-off-worlds-through-characterization-by-proxy/

Herschel Links Water In Jupiter’s Stratosphere To 1994 Comet Impact


Distribution of water in Jupiter's stratosphere. Credit: Water map: ESA/Herschel/T. Cavalié et al.; Jupiter image: NASA/ESA/Reta Beebe (New Mexico State University)

Distribution of water in Jupiter’s stratosphere. Credit: Water map: ESA/Herschel/T. Cavalié et al.; Jupiter image: NASA/ESA/Reta Beebe (New Mexico State University)

Astronomers have finally found direct proof that almost all water present in Jupiter’s stratosphere was delivered by comet Shoemaker-Levy 9, which struck the planet in 1994. The result is based on new data from Herschel that revealed more water in Jupiter’s southern hemisphere, where the impacts occurred, than in the north as well as probing the vertical distribution of water in the planet’s stratosphere.

The origin of water in the upper atmospheres of the Solar System’s giant planets has been debated for almost two decades. Astronomers were quite surprised at the discovery of water in the stratosphere – an intermediate atmospheric layer – of Jupiter, Saturn, Uranus and Neptune, which dates to observations performed with ESA’s Infrared Space Observatory (ISO) in 1997. While the source of water in the lower layers of their atmospheres can be explained as internal, the presence of this molecule in their upper atmospheric layers is puzzling due to the scarcity of oxygen there – its supply must have an external origin. Since then, astronomers have investigated several possible candidates that may have delivered water to these planets, from icy rings and satellites to interplanetary dust particles and cometary impacts.

Answers are now starting to flow in from studies using ESA’s Herschel space observatory. Herschel boasts unprecedented sensitivity as well as high spatial and spectral resolution at the far-infrared wavelengths, where many water emission lines can be observed.

Full Story: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=51720
Also: http://www.esa.int/Our_Activities/Space_Science/Herschel/Herschel_links_Jupiter_s_water_to_comet_impact
Also: http://www.aanda.org/index.php?option=com_content&task=view&id=922&Itemid=277

Star Factory In The Early Universe Challenges Galaxy Evolution Theory


A team including Mat Page (UCL Space and Climate Physics) has discovered an extremely distant galaxy making stars more than 2000 times faster than our own Milky Way. Seen at a time when the Universe was less than a billion years old, its mere existence challenges our theories of galaxy evolution. The observations were carried out using the European Space Agency’s Herschel Space Observatory.

The galaxy, known as HFLS3, appears as little more than a faint, red smudge in images from the Herschel Multi-tiered Extragalactic Survey (HerMES). Yet appearances can be deceiving: this small smudge is actually a star-building factory, furiously transforming gas and dust into new stars.

Our own Milky Way makes stars at a rate equivalent to one solar mass per year, but HFLS3 is seen to be churning out new stars at more than two thousand times more rapidly. This is one of the highest star formation rates ever seen in any galaxy.

Full Story: https://www.ucl.ac.uk/maps-faculty/maps-news-publication/maps1306

Dying Supergiant Stars Implicated In Hours-long Gamma-Ray Bursts


GRB 111209A exploded on Dec. 9, 2011. Credit: NASA/Swift/B. Gendre (ASDC/INAF-OAR/ARTEMIS)

GRB 111209A exploded on Dec. 9, 2011. Credit: NASA/Swift/B. Gendre (ASDC/INAF-OAR/ARTEMIS)

Three unusually long-lasting stellar explosions discovered by NASA’s Swift satellite represent a previously unrecognized class of gamma-ray bursts (GRBs). Two international teams of astronomers studying these events conclude that they likely arose from the catastrophic death of supergiant stars hundreds of times larger than the sun.

GRBs are the most luminous and mysterious explosions in the universe. The blasts emit surges of gamma rays — the most powerful form of light — as well as X-rays, and they produce afterglows that can be observed at optical and radio energies. Swift, Fermi and other spacecraft detect an average of about one GRB each day.

“We have seen thousands of gamma-ray bursts over the past four decades, but only now are we seeing a clear picture of just how extreme these extraordinary events can be,” said Bruce Gendre, a researcher now associated with the French National Center for Scientific Research who led this study while at the Italian Space Agency’s Science Data Center in Frascati, Italy.

Full Story: http://www.nasa.gov/mission_pages/swift/bursts/supergiant-stars.html

Hubble Captures Comet ISON

April 24, 2013 1 comment

Credit: NASA, ESA, J.-Y. Li (Planetary Science Institute), and the Hubble Comet ISON Imaging Science Team

Credit: NASA, ESA, J.-Y. Li (Planetary Science Institute), and the Hubble Comet ISON Imaging Science Team

This NASA Hubble Space Telescope image of Comet C/2012 S1 (ISON) was photographed on April 10, when the comet was slightly closer than Jupiter’s orbit at a distance of 386 million miles from the Sun (394 million miles from Earth).

Even at that great distance the comet is already active as sunlight warms the surface and causes frozen volatiles to sublimate. A detailed analysis of the dust coma surrounding the solid, icy nucleus reveals a strong jet blasting dust particles off the sunward-facing side of the comet’s nucleus.

Preliminary measurements from the Hubble images suggest that the nucleus of ISON is no larger than three or four miles across. This is remarkably small considering the high level of activity observed in the comet so far, said researchers. Astronomers are using these images to measure the activity level of this comet and constrain the size of the nucleus, in order to predict the comet’s activity when it skims 700,000 miles above the Sun’s roiling surface on November 28.

Full Story: http://hubblesite.org/newscenter/archive/releases/2013/14/image/a/
Also: http://www.umdrightnow.umd.edu/news/hubble-brings-faraway-comet-view