Exoplanet Image Update

April 1, 2005 | The purported planet around GQ Lupi may not be a planet at all. The newly released paper by Neuhauser and his colleagues suggest that the object in question could be as much as 42 Jupiter masses. Brown dwarfs are, by definition, between 13 and about 75 Jupiter masses (S&T: May issue, page 34).

Sky & Telescope will continue to report on this story as more details come to light.

Exoplanet Imaged?

March 31, 2005 | For centuries, astronomers have dreamed of taking a direct image of a planet orbiting another star. In April 2004, a team led by Gael Chauvin (European Southern Observatory) claimed to have imaged a 5-Jupiter-mass planet orbiting the brown dwarf 2MASS 1207 (a claim that has been bolstered by subsequent observations). Now, a team led by Ralph Neuhäuser (University of Jena, Germany) says it has imaged an even lower-mass planet: one with perhaps just twice the mass of Jupiter. The paper announcing this discovery has been accepted for publication in Astronomy & Astrophysics, a prestigious European journal, but it has not yet been seen by the astronomy community at large. Neuhäuser's team took images of the object with the NACO infrared adaptive-optics camera on one of the four 8.2-meter Very Large Telescope reflectors in Chile.

According to data posted at the Extrasolar Planets Encyclopedia, Neuhauser's team claims that the planet has a mass only twice that of Jupiter, with an uncertainty of only plus or minus 1 Jupiter mass. The low-mass companion is 0.7 arcseconds from the star, meaning it orbits its host star at least 50 times the Earth-Sun distance. With that large separation, it must take about 1,200 years to orbit the star. The star, GQ Lupi, is likely to be at most only a few million years old. It lies about 450 light-years from Earth. It is a classical T Tauri star, meaning it is still accreting material from a circumstellar disk.

The astronomers estimated the companion object's low mass from its age and temperature (about 2,000° Kelvin). If the planet's low mass is confirmed, it will be represent a milestone in astronomy history: the first planet imaged around a true star other than the Sun.

But Ben Zuckerman (University of California, Los Angeles), a member of Chauvin's team, expresses caution. "The plus or minus 1 Jupiter mass seems like an incredibly tiny error bar to me," he says. Noting that he has not yet seen Neuhauser's paper, Zuckerman points out that the planet's estimated mass must be based on theoretical models and the host star's estimated age, both of which are fraught with uncertainty for such a young star. Zuckerman also points out that the star and planet are buried deep within a cloud of gas and dust, which makes it difficult to calculate the planet's actual luminosity, which would in turn affect its mass estimate. Since the star is still accreting material, there is every reason to think that its companion must also be accreting material from the surrounding cloud. "Who knows what its final mass will be when the system is free of the molecular cloud," says Zuckerman.

David Bushnell (1913–2005)

March 31, 2005 | David Bushnell, the founder of Bushnell Optical Corporation, died of cancer on March 24th. He was 91.

Bushnell founded the company in 1947 as a mail-order business. It is now based in Overland Park, Kansas, and is a global manufacturer and supplier of binoculars, telescopes, spotting scopes, riflescopes, night-vision gear, laser rangefinders, eyeglasses, and other branded consumer optical products.


You must be logged in to post a comment.