Many stars close to the Sun have familiar names, like the Centauri triple-star system, Barnard's Star, Epsilon Eridani and Tau Ceti. But the catalog of nearby stars is by no means complete, as we are reminded periodically by the discovery of stars showing large proper motion as observed from Earth. That motion flags the object as close, but the fact that so many of the galaxy's stars are M-class red dwarfs (up to 70 percent in some estimates) makes detecting them tricky. These are small, dim stars; some may have been in our catalogs for years before astronomers realized how close they were. Some scientists, in fact, measure the number of missing stellar systems at 25 percent or more, even so close as 10 parsecs from the Sun. Now an international team of researchers has found three of the missing stars. Using data from the Two-Micron All Sky Survey (2MASS), the Deep Near Infrared Survey (DENIS) and the SuperCOSMOS Sky Survey (SSS), the team uncovered the three close neighbors by...

The European Space Agency's DARWIN mission is all about detecting Earth-like planets, as well as analyzing their atmospheres and determining their ability to sustain life. With the mission currently in its 'definition' phase, where parameters are determined and designs weighed, Lisa Kaltenegger (Harvard-Smithsonian Center for Astrophysics) has made her Ph.D work in astrophysics available to interested scientists. Written for Karl Franzens University in Graz, Kaltenegger's study presents her work with the DARWIN team at the European Space Agency. Here you'll find an evaluation of alternative designs and mission targets; the section on defining the features of a habitable world alone is worth the download of this enormous PDF file. Scheduled for launch some time after 2014, DARWIN is a space-based interferometer designed to operate by pooling the data from free-flying craft working in tandem. At the heart of Kaltenegger's work is a discussion of target star selection for DARWIN. As...

The race to confirm the first image of an exoplanet takes yet another turn with the announcement that a young brown dwarf some 200 light years from Earth really is orbited by a planet that is five times the mass of Jupiter. We looked at this brown dwarf, called 2M1207A, in an entry last September. When the object visually near it was first discovered about a year ago, there remained the possibility that the apparent planet was a background star. But new observations seem to rule this out. "Our new images show convincingly that this really is a planet, the first planet that has ever been imaged outside of our solar system," says Gael Chauvin, astronomer at ESO and leader of the team of astronomers who conducted the study. And Benjamin Zuckerman, UCLA professor of physics and astronomy and a member of the international team working on 2M1207A, adds this: "The two objects - the giant planet and the young brown dwarf - are moving together; we have observed them for a year, and the new...

Finding solar systems similar to our own is a continuing quest for planet hunters. Now a star called HD69830, some 41 light years from Earth, has been found to contain a thick band of warm dust that may be an asteroid belt. Although planets have yet to be detected around the star, the find is exciting because HD69830 is similar to the Sun in age and size. And just as Jupiter seems to provide an outer limit to our own asteroid belt, there are suspicions that the asteroid belt around this star may be contained by the gravitational influence of a gas giant planet. If such planets exist around HD69830, they'll likely be spotted by future planet-hunting missions like SIM, the Space Interferometry Mission, which is scheduled for a 2011 launch. But exoplanetary systems continue to confound our expectations. The newly discovered belt is not only 25 times as dense as our own, it's also much closer to its star. Imagine a thick belt of primordial debris located inside the orbit of Venus,...

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.

NASA will announce "... major findings about planets outside our solar system..." in a press conference to be held at 1 PM EST on Wednesday March 23. NASA TV is planning to cover the event live. The new data come from the Spitzer Space Telescope, which works in the infrared and most recently made the news with its findings of remarkably bright galaxies hidden by dust some 11 billion light years away. The NASA press release can be read here.

PlanetQuest is a distributed computing project aimed at using spare computer cycles to search for extrasolar planets. The search will use the transit method, in which a planet is detected when it crosses the face of its primary as seen from Earth. That requires subjecting the data from thousand of stellar images to analysis, a job that would tax the largest supercomputer, but perhaps not the kind of distributed network that SETI@Home has already put to work in its search for extraterrestrial intelligence. Nobody knows for sure how many stars have planets that line up edge-on to our own line of sight, but estimates run between 0.5 and 10 percent. Instead of studying a single star for long periods, as is done in the radial velocity method that has found most extrasolar planets so far, the transit approach has to rely on images of highly crowded star regions, where tens of thousands of stars can be viewed at once. The best area, then, is in the plane of the Milky Way. Stars captured in...

Can a star look like a planet? Evidently so, to judge from observations of the star OGLE-TR-122. Astronomers working at the European Southern Observatory's Paranal Observatory in Chile have discovered that the star experiences a drop in brightness every 7 days 6 hours and 27 minutes, a strong indication (when combined with radial velocity measurements) that a low-mass star is regularly moving in front of its larger companion as seen from Earth. Measuring radial velocity allows scientists to discriminate between stars and planets as the cause of the brightness variations. The OGLE (Optical Gravitational Lensing Experiment) survey has been studying changes in the brightness of stars that could be caused by the transit of such unseen companions. And this one, christened OGLE-TR-122b, turns out to be a rarity indeed. It adds up to one-eleventh of the Sun's mass, making it the smallest known star, only 16 percent larger than Jupiter though 96 times as massive as that planet. "This result...

A story in a recent issue of New Scientist covers the possibility of planets around brown dwarfs, focusing on the work of Kevin Luhman of the Harvard-Smithsonian Center for Astrophysics. Centauri Dreams looked at this study in a previous posting, but writer Hazel Muir adds a further comment on habitability around such worlds based on Luhman's work: It is conceivable that such planets, if they form, could be habitable. The surface temperature of the mini brown dwarf is 2300 kelvin, so a planet 1.5 to 7 million kilometres away could host liquid water. Planets very close to a brown dwarf would be scorched at first, but would become hospitable as the star cooled. Brown dwarfs take a long time to cool, so the planet could remain habitable long enough for life to evolve. Another thought, from Andrew Collier Cameron at the University of St. Andrews in the UK, who is quoted in the article: brown dwarfs might be useful hunting grounds for exoplanets, given the faintness of the brown dwarf...