An interesting piece in Nature‘s online edition describes the race to see who has actually imaged a planet around another star. As discussed in Centauri Dreams earlier, a team in Chile at the European Southern Observatory has used infrared to reveal what may be a planet circling the star 2M1207, a brown dwarf, but there is still no conclusive evidence that the planetary candidate actually orbits the star. But another team, from Pennsylvania State University and using Hubble images, also believes it has found such an object, though they won’t yet name the star or discuss its location for fear of being scooped.
If the PSU object is indeed a planet, it is between five and ten times the mass of Jupiter and roughly 100 light years from Earth, in an orbit similar to that of Neptune around our Sun. Infrared is useful in both sets of observations because the contrast between a star and its planet is a thousand times less at these wavelengths; in visual light, the glow of a planet is completely drowned out by the parent star. It’s also useful to study brown dwarfs or, as in the PSU work, white dwarfs, because the light from these objects is far less likely to overwhelm the image of any orbiting planets.
The kicker: any of these objects might be stars themselves, simply far away and positioned along a line of sight that makes them look like planetary companions. In an earlier Nature piece on the PSU work (free registration required), team leader Steinn Sigurdsson says this: “We could be unlucky and find these things are distant, reddened, low-mass stars in the galactic halo, or high-redshift quasars.”
All in all, it’s far too early to celebrate a planetary detection around either of these stars, but the next few months may lead to observations that confirm one or both.
