61 Vir b (simulation by J. Langton, Principia College)

The ranks of the super Earths and the sub Neptunes continue to grow! In two papers that have been accepted by the Astrophysical Journal, and which will be coming out in tomorrow’s astro-ph mailing, the Earthbound Planet Search team is announcing the detection of very low mass planets orbiting the nearby solar twins 61 Vir and HD 1461. (Link to paper #1, link to paper #2).

The 61 Vir system is particularly compelling. The radial velocity data for this star indicate that at least three planets are present, with an architecture that’s quite a bit more crowded than the Sun’s terrestrial planet zone:

The innermost planet, 61 Vir b, with Msin(i)~5.5 Earth masses, has a radial velocity half-amplitude K=2.15 m/s, which puts it in league with Gl581e (with K=1.9 m/s) and HD40307b (with K=2.0 m.s) as the lowest-amplitude Doppler detections to date.

We’ve adopted the Systemic Console software to analyze the Doppler velocities that are produced by the Earthbound Planet Search. I’ve written a tutorial (link here) that explores the 61 Vir dataset in detail, and shows how the planets are extracted.