Beta Pictoris: Exoplanet Caught on the Move
For the first time, astronomers have been able to directly follow the motion of an exoplanet as it moves to the other side of its host star, Beta Pictoris, which is only 12 million years old and 75% more massive than hte Sun. It is located about 60 light-years away towards the constellation of Pictor and is one of the best-known examples of a star surrounded by a dusty debris disc.
The team of astronomers used the NAOS-CONICA instrument (or NACO), mounted on one of the 8.2-metre Unit Telescopes of ESO’s Very Large Telescope (VLT), to study the immediate surroundings of Beta Pictoris in 2003, 2008 and 2009, revealing the object on the other side of the disc after having been hidden either behind or in front of the star. This confirmed that the source indeed was an exoplanet and that it was orbiting its host star.
The planet, which is about nine times the size of Jupiter, has the smallest orbit so far of all directly imaged exoplanets, lying as close to its host star as Saturn is to the Sun. Scientists believe that it may have formed in a similar way to the giant planets in the Solar System. Because the star is so young, this discovery proves that gas giant planets can form within discs in only a few million years, a short time in cosmic terms.
Image: The above composite shows the reflected light on the dust disc in the outer part. In the central part, the observations of the planet obtained in 2003 and autumn 2009 are shown. The possible orbit of the planet is also indicated, albeit with the inclination angle exaggerated.
Image: Artist’s impression of the planet inside the disc of Beta Pictoris.
Credit: ESO |
Other: Astronomy.com, SPACE.com, Bad Astronomy, Wired
‘This Planet Tastes Funny,’ According to Spitzer
An unusual, methane-free world is partially eclipsed by its star in this artist’s concept. NASA’s Spitzer Space Telescope has found evidence that a hot, Neptune-sized planet orbiting a star beyond our sun lacks methane — an ingredient common to many planets in our own solar system
Methane is present on our life-bearing planet, manufactured primarily by microbes living in cows and soaking in waterlogged rice fields. All of the giant planets in our solar system have methane too, despite their lack of cows. Neptune is blue because of this chemical, which absorbs red light. Methane is a common ingredient of relatively cool bodies, including “failed” stars, which are called brown dwarfs.
Models of planetary atmospheres indicate that any world with the common mix of hydrogen, carbon and oxygen, and a temperature up to 1,000 Kelvin (1,340 °F) should have a large amount of methane and a small amount of carbon monoxide. The planet illustrated here, called GJ 436b is about 800 Kelvin (or 980 °F) — it was expected to have methane but Spitzer’s observations showed it does not. Theorists are going to be quite busy trying to figure this one out.
The discovery brings astronomers one step closer to probing the atmospheres of distant planets the size of Earth. The methane-free planet, called GJ 436b, is about the size of Neptune, making it the smallest distant planet that any telescope has successfully “tasted,” or analyzed. The finding demonstrates the diversity of exoplanets, and indicates that models of exoplanetary atmospheres need to be revised.
Small, Ground-Based Telescope Images Three Exoplanets
This infrared image shows the light from three planets orbiting a star 120 light-years away. The planets’ star, called HR8799, is located at the spot marked with an “X.” This picture was taken using a small, 1.5-meter portion of the Palomar Observatory’s Hale Telescope, north of San Diego, Calif.
This is the first time a picture of planets beyond our solar system has been captured using a telescope with a modest-sized mirror. Astronomers took painstaking efforts to push current technology to the point where such a small mirror could be used, to minimize the glare from the star and reveal the dim glow of the much fainter planets.
The three planets, called HR8799b, c and d, are thought to be gas giants like Jupiter, but more massive. They orbit their host star at roughly 24, 38 and 68 times the distance between our Earth and sun, respectively. It’s possible that rocky worlds like Earth circle closer to the planets’ star, but with current technology, they would be impossible to see under the star’s glare.
Source: NASA’s Jet Propulsion Laboratory
Turning Planetary Theory Upside Down
Scientists have announced the discovery of nine new transiting exoplanets. When these new results were combined with earlier observations of transiting exoplanets astronomers were surprised to find that six out of a larger sample of 27 were found to be orbiting in the opposite direction to the rotation of their host star — the exact reverse of what is seen in our own Solar System.
The new discoveries provide an unexpected and serious challenge to current theories of planet formation. They also suggest that systems with exoplanets of the type known as Hot Jupiters are unlikely to contain Earth-like planets.
Planets are thought to form in the disc of gas and dust (proto-planetary disc) rotating around a young star in the same direction as the star itself, in more or less the same plane. Since Hot Jupiters have cores made of rock and ice particles found in the outer reaches of planetary systems, they form far from their star, and then migrate inwards to orbit it much closer via gravitational interactions with the proto-planetary disc.
A theory suggests that the proximity of hot Jupiters to their stars is not due to interactions with the dust disc at all, but to a slower evolution process involving a gravitational war with more distant planetary or stellar companions over hundreds of millions of years. After these disturbances have bounced a giant exoplanet into a tilted and elongated orbit, it would suffer tidal friction, losing energy every time it swung close to the star. It would eventually become parked in a near circular, but randomly tilted, orbit close to the star. A dramatic side-effect of this process is that it would wipe out any other smaller Earth-like planet in these systems.
Image: Artist’s impression of the planet WASP 8b transiting its parent star. Credit: ESO
Royal Astronomical Society
Rocky planets ‘are commonplace’ in our Galaxy
An international team of astronomers have discovered compelling evidence that rocky planets are commonplace in our Galaxy. They surveyed white dwarfs, the compact remnants of stars that were once like our Sun, and found that many show signs of contamination by heavier elements and possibly even water, improving the prospects for extraterrestrial life.
It was believed that the source of metals in these polluted white dwarfs was the interstellar medium, the tenuous gas between the stars. But by using data from the Sloan Digital Sky Survey (SDSS), they found that at least 3% and perhaps as much as 20% of all white dwarfs are contaminated by debris most likely in the form of rocky minor planets.
This implies that a similar proportion of stars like our Sun, as well as stars that are a little more massive like Vega and Fomalhaut, build terrestrial planetary systems. It also appears that a significant fraction of these stars are polluted with material that contained water, with important implications for the frequency of habitable planets around other stars.
If internal water is present in a substantial fraction of asteroids around other stars, like those that contaminated the white dwarfs, it is conceivable that at least simple life may be common throughout the Galaxy.
Image: An artist’s impression of a massive asteroid belt in orbit around a star.
Source: Royal Astronomical Society
First Temperate Exoplanet Sized Up
This artist’s impression shows the transiting exoplanet Corot-9b. Discovered by combining observations from the CoRoT satellite and the ESO HARPS instrument, Corot-9b is the first “normal” exoplanet that can be studied in great detail. This planet has the size of Jupiter and an orbit similar to that of Mercury.
It orbits a star similar to the Sun located 1500 light-years away from Earth towards the constellation of Serpens (the Snake). Corot-9b passes in front of its host star every 95 days, as seen from Earth. This “transit” lasts for about 8 hours. Like our own giant planets, Jupiter and Saturn, the planet is mostly made of hydrogen and helium, and it may contain up to 20 Earth masses of other elements, including water and rock at high temperatures and pressures.
Cannibal star is devouring a planet
The planet, whose discovery was reported last year, is a “gas giant” with a mass about 40 percent greater than that of Jupiter, the biggest planet of our Solar System, and with a radius 79 percent bigger. But whereas Jupiter takes nearly 12 years to plod around the Sun, it takes WASP-12b a mere 26 hours to race around its star, WASP-12, located in the constellation of Auriga
So close is its orbit that the gravitational tug of the star has helped to squeeze the planet into a prolate shape. Searing heat is stripping away layers of the gas, whose mass is then captured by the star. The disk of captured matter around the star may mask “a detectable resonant super-Earth,” whose presence may cause WASP-12b to orbit in a remarkably egg-shaped path
Image: This picture relased by the European Space Agency shows an artist’s impression of what a “hot Jupiter” (planets so close to their stars they have short orbital periods) might look like. One such “hot Jupiter”, the star WASP-12b, 600 light years from Earth, is slowly gobbling up one of its own planets.
These are computer-generated images of the development of severe weather patterns on the exoplanet HD 80606b during the days after its closest approach to its parent star, located about 200 light years away in the constellation of Ursa Major. The blue glow of the crescent is starlight that has been scattered and reflected by the planet. The night side appears reddish orange as it glows in infrared light with its own internal heat. The simulation is based on infrared data taken in late 2007 by the Spitzer Space Telescope. [SPACE.com, APOD]
Remarkable Styrofoam Planet Is Among Five New Exoplanet Discoveries
NASA’s dedicated exoplanet hunter, the Kepler space telescope, has turned up five new planets. One of the planets is bigger than Jupiter but as light as styrofoam, and the findings only get crazier.
All five of the exoplanets are bigger than Earth, and four of them are significantly bigger than Jupiter. As the diagram up top indicates, all five are hotter than molten lava, and two of them are even hotter than the melting point of iron. Indeed, those two planets are actually hotter than the stars they orbit, which is completely unprecedented. The planets also have incredibly quick orbits, with some taking as little as three to five days to complete a revolution around their star.
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NASA’s Kepler Space Telescope Discovers its First Five Exoplanets
NASA’s Kepler space telescope, designed to find Earth-size planets in the habitable zone of sun-like stars, has discovered its first five new exoplanets, or planets beyond our solar system.
(via spacethebeyond, spacefellowship.com)
NASA’s new exoplanet-hunting Kepler space telescope has detected the atmosphere of a known giant gas planet, demonstrating the telescope’s extraordinary scientific capabilities. The discovery will be published Friday, Aug. 7, in the journal Science.
The find is based on a relatively short 10 days of test data collected before the official start of science operations. Kepler was launched March 6, 2009, from Cape Canaveral Air Force Station in Florida. The observation demonstrates the extremely high precision of the measurements made by the telescope, even before its calibration and data analysis software were finished.