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Stories · 7
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NASA's Hubble Telescope Discovers An 'Evaporating' Planet (usatoday.com)
Researchers at the University of Geneva Switzerland have used NASA's Hubble telescope to find an exoplanet that's evaporating. The exoplanet, GJ 3470b, shows signs of losing hydrogen in its atmosphere, causing it to shrink. USA Today reports: The study is part of exploration into "hot Neptunes," planets that are the size of Neptune, sit very close to their star, and have atmospheres as hot at 1,700 degrees Fahrenheit, says NASA. Finding a "hot Neptune" is rare because they sit so close to their star and tend to evaporate more quickly. In the case of GJ 3470b, scientists classify it as a "warmer" Neptune because it sits farther away from its star. The exoplanet discovered by astronauts is losing its atmosphere at a rate 100 times faster than a previous "warmer" Neptune planet discovered a few years before, according to a study published Thursday in the journal "Astronomy & Astrophysics." The planet sits 3.7 million miles from its star. For comparison, Earth is 92.9 million miles from the sun. Researchers say these "hot Neptune" planets shrink in size and morph into "Super Earths," versions of our planet that are massive and more rocky. -
Star's Black Hole Encounter Puts Einstein's Theory of Gravity To the Test (sciencemag.org)
An anonymous reader quotes a report from Science Magazine: For more than 20 years, a team of astronomers has tracked a single star whipping around the supermassive black hole at the center of our galaxy at up to 25 million kilometers per hour, or 3% of the speed of light. Now, the team says the close encounter has put Albert Einstein's theory of gravity to its most rigorous test yet for massive objects, with the light from the star stretched in a way not prescribed by Newtonian gravity. In a study announced today, the team says it has detected a distinctive indicator of Einstein's general theory of relativity called "gravitational redshift," in which the star's light loses energy because of the black hole's intense gravity. The star, called S2, is unremarkable apart from a highly elliptical orbit that takes it within 20 billion kilometers, or 17 light-hours, of the Milky Way's central black hole -- closer than any other known star. A team led by Reinhard Genzel at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany, has been tracking S2 since the 1990s, first with the European Southern Observatory's (ESO's) 3.6-meter New Technology Telescope in Chile's Atacama Desert and later with ESO's Very Large Telescope (VLT), made up of four 8-meter instruments. Ghez's team at UCLA also began to observe the star around the same time with the twin 10-meter Keck telescopes in Hawaii. In a paper published today in Astronomy & Astrophysics, Genzel's group reports seeing the combined action of the relativistic effects, with the black hole's gravity redshifting S2's radial velocity by 200 kilometers per second, a small fraction of its overall speed. The results match closely with the predictions of relativity and are inconsistent with Newtonian gravity. -
Star Spotted Speeding Near Black Hole at Centre of Milky Way (theguardian.com)
Astronomers have observed a star speeding close to the massive black hole at the centre of the Milky Way for the first time. From a report: The observations, made using the Very Large Telescope in Chile, tracked a star called S2 as it passed through the extreme gravitational field at the heart of our galaxy. As the star approached its nearest point to the black hole on 19 May, it was accelerated to mind-boggling speeds, causing it to be subject to effects predicted by Einstein's theory of general relativity. Astronomers had been tracking the star and preparing to make the observations for the past 16 years -- the time taken for the star to complete a single elliptical orbit of the black hole. "We have been preparing intensely for this event over several years, as we wanted to make the most of this unique opportunity to observe general relativistic effects," said Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany, who led the international team. The findings can be found here. -
Advanced Civilizations Probably Don't Exist In Our Galactic Neighborhood
schwit1 writes: New observations of the best candidate galaxies now suggest that advanced civilizations are very rare or don't exist in the local universe. Researchers looked at several hundred nearby galaxies that emitted a high amount of mid-infrared radiation (abstract), which could possibly be produced as the waste heat from civilizations using energy on galactic scales.
They found: "The presence of radio emission at the levels expected from the correlation, suggests that the mid-IR emission is not heat from alien factories but more likely emission from dust — for example, dust generated and heated by regions of massive star formation. As Professor Garrett explains: 'the original research at Penn State has already told us that such systems are very rare but the new analysis suggests that this is probably an understatement, and that advanced Kardashev Type III civilizations basically don't exist in the local Universe.'"
Obviously, the uncertainty of these results is quite high. Nonetheless, the results indicate that either humanity really is the only intelligent species in this part of the universe, or advanced civilizations are far more efficient in their use of energy than is reasonable to assume. -
13-Billion-Year-Old Alien Worlds Discovered
astroengine writes "Two exoplanets have been discovered by scientists at the Max-Planck Institute for Astronomy orbiting the star HIP 11952. But according to conventional thinking, these worlds shouldn't exist. You see, HIP 11952 is a 'metal-poor star and planetary formation is hindered around stars with low metallicity (PDF). This isn't the only thing; as metal-poor stars were the first stars to form when the Universe was very young, these two worlds also formed around the same time. They are therefore the most ancient exoplanets discovered to date." -
The Rain On Saturn Falls Mainly From Space
The Bad Astronomer writes "Astronomers have discovered that the source of water in Saturn's upper atmosphere is none other than the geysers erupting from its moon Enceladus. The geysers spew water into space, most of which is lost. A small amount, though, falls to Saturn... equivalent to only about 7.5 kilos/second over the entire planet (PDF). A typical rainfall on Earth is 42 trillion times heavier." -
Evidence For 200-Year-Old Comet Impact On Neptune
astroengine writes "Astronomers using ESA's Herschel space observatory have spotted evidence of a cometary impact in Neptune's upper atmosphere (publication, PDF). Whereas impact craters on rocky planetary bodies can remain for billions of years, an impact in the dynamic atmospheres of gas giants aren't obvious, especially if long periods of time have elapsed. This ultimate 'cold case' tracked the unusual distribution of carbon monoxide in Neptune's stratosphere, a sure sign it was deposited there by an external source. Once they realized they were looking at a comet impact, researchers were able to deduce when the impact occurred: 200 years ago."