AAS : Observers 1 - 1 Theorists (late result)
Astronomy can sometimes feel like an arms race between observers and theorists. Both groups are often convinced that they’re completely right and - at least over a drink at the end of the day - take great pride in being ahead of the game. The latest battleground is in the field of extrasolar planets, and results from this lunchtime’s press conference will have cheered both sides.
Rory Barnes of the University of Arizona scored an early goal for the theorists, proudly announcing the first successful prediction of a planet since Neptune was discovered more than 160 years ago. His theory suggests that systems with multiple planets are often dynamically unstable, meaning that a small change in their orbits would lead to chaos. He also suggested that all such positions tend to have planets - solar systems tend to be ‘packed’. The system he studied, HD 74156, was already known to have two planets, and computer simulations indicated the presence of a gap. Sure enough, a couple of months ago, a planet was found in the gap just as Barnes predicted. Sara Seager, who gave an excellent talk on the field yesterday, congratulated him, and pointed out that this field littered with predictions which turn out to be wrong - but not this one.
Any theorists who were looking forward to the full time whistle should have listened to Carl Melis’ talk just a few minutes later. Looking through an old data set (from the IRAS satellite which went into orbit in 1983). His team have found two very confusing stars. They look like a type of young star called classical T Tauri stars, which have dusty disks, jets and lots of infrared light (see image above). So do the two stars Melis was studying, but there isn’t much lithium in them, which indicates that they are old. (Stars `burn’ lithium so its concentration should be highest when they’re young). So these are old stars pretending to be young, and possibly undergoing a second wave of planet formation. No-one predicted this, and I’m looking forward to seeing what the reaction might be and what explanations people will come up with.
