The recent image of a possible planet around the star GQ Lupi has met with understandable enthusiasm in the press, but we still don't know whether the small object just to the right of the star in the image below is a planet or a brown dwarf. The boundary between brown dwarf and planet is tricky terrain, but the European Southern Observatory fixes it at roughly 13 Jupiter masses, which is the critical mass needed to ignite deuterium. Brown dwarfs, then, are objects heavier than that. But the observations of Ralph Neuhäuser and colleagues do not provide a direct estimate of the smaller object's mass. Because GQ Lupi and its companion presumably formed at the same time, then the new object is young, and traditional models for such calculations may not apply. But using them, according to a press release from the ESO, implies that the object is somewhere between 3 and 42 Jupiter masses. In other words, based on what we can determine so far, GQ Lupi b is either a planet or a brown dwarf....

The planetary systems so far discovered around other stars have generally been dominated by huge, gas giant worlds, many with so-called 'hot Jupiters' that orbit extremely close to their parent star. And that makes sense, given that a major method used for detecting exoplanets relies upon the star's 'wobble' as it is influenced by such high-mass objects. We're not yet at the point where Earth-sized planets can be found, although we've reduced the detection size down to Neptune-class objects, with better things to come. But don't assume that even the systems discovered so far are without terrestrial planets. As many as half of them may harbor habitable worlds, according to work by Barrie Jones, Nick Sleep, and David Underwood at the Open University in Milton Keynes (UK), which was presented today at the Royal Astronomical Society National Astronomy Meeting in Birmingham. The team used computer models to analyze the gravitational effects of known exoplanets on other, undiscovered...

Sky & Telescope is reporting that the purported planet around GQ Lupi may not be a planet but a brown dwarf. The magazine evidently draws this conclusion from a study of the paper by Ralph Neuhaeuser and colleagues that is to run in an upcoming issue of Astronomy & Astrophysics. "The newly released paper by Neuhauser and his colleagues suggests that the the object in question could be as much as 42 Jupiter masses. Brown dwarfs are, by definition, between 13 and 74 Jupiter masses," the magazine reports. Meanwhile, data on the possible GQ Lupi planet can be found at the Extrasolar Planets Encyclopedia. The preprint of the Neuhaeuser paper, "Evidence for a co-moving sub-stellar companion of GQ Lup," is available here. A key excerpt from the paper: The most critical point in the mass determination of the companion (candidates) of GQ Lup and 2M1207 are the models, which may be off by an unknown factor for low ages (few Myrs); they need to be calibrated, before the mass of such companions...

Space.com is reporting that a European team led by Ralph Neuhaeuser of the Astrophysical Institute & University Observatory has obtained a photograph of an extrasolar planet around GQ Lupi, a young star about 400 light years from Earth. The image shows a faint object the team believes to orbit some 100 AU from its parent star, an apparently young and hot planet. From the article: The planet is about 3,140 degrees Fahrenheit (2000 Kelvin) -- not the sort of place that would be expected to support life. Neuhaeuser's team has also detected water in the planet's atmosphere. The world is expected to be gaseous, like Jupiter. It is about twice the diameter of Jupiter. The mass estimate -- one to two times that of Jupiter -- is "somewhat uncertain," Neuhaeuser said. The planet is three times farther from GQ Lupi than Neptune is from our Sun. "We should expect that the planet orbits around the star, but at its large separation one orbital period [a year] is roughly 1,200 years, so that...

As discussed in yesterday's entry, being able to work with actual light from distant planets is a major breakthrough. It opens the possibility of studying characteristics like temperature and atmospheric composition, further fusing astronomy with the nascent science of astrobiology. And with the Spitzer Space Telescope's proven ability to make such observations, we can expect a whirlwind of exoplanetary data ahead. A few further details from yesterday's announcements: A study of the work on HD 209458b, a 'hot Jupiter' that orbits its parent star in 3.5 days, ran in today's online edition of Nature. The paper is Deming, D., Seager, S. et al., "Infrared radiation from an extrasolar planet." Dr. Sara Seager of the Carnegie Institution, a co-author of the study, provided more about HD 209458b: "This planet was discovered indirectly in 1999 and was later found to transit its star--the star dims as the planet moves in front of it during the course of the planet's orbit. With Spitzer, we...

Light from two planets orbiting other stars has now been directly detected by the Spitzer Space Telescope, in findings announced today at a NASA news conference. Spitzer scrutinized both planets using the 'transit' method, in which a planet eclipses its star and blocks a small fraction of its light. The space-based telescope has been able to detect not only the primary transit but the secondary eclipse, occurring when a planet comes out from behind its star on the far side of its orbit. It thus became possible for astronomers to subtract the planetary 'signal' from the otherwise overwhelming light of the parent star, the first confirmed detection of the light from extrasolar worlds. Both planets fall into the category of 'hot Jupiters' -- massive worlds that orbit at extremely close distances from their primaries. The first (studied with Spitzer's Infrared Array Camera) is TrES-1, orbiting its star at a distance of four million miles and boasting a temperature of 1340 degrees...

"Astronomers will announce major findings about planets outside our solar system, known as extrasolar planets, at a NASA Science Update at 3 p.m. EST today." So says a media advisory just out from the agency. NASA TV plans to carry the event, which will discuss discoveries made by the Spitzer Space Telescope. The panelists: Dr. Drake Deming, chief, planetary systems laboratory, NASA's Goddard Space Flight Center, Greenbelt, Md. Dr. David Charbonneau, assistant professor of astronomy, Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. Dr. Alan Boss, staff research astronomer, Department of Terrestrial Magnetism, Carnegie Institution of Washington Dr. Kim Weaver, moderator; Spitzer program scientist, NASA's Science Mission Directorate, Washington.