Astronomers detect smallest extrasolar planets yet

Bob Kopp writes "A team of astronomers using Keck Observatory has discovered the smallest extrasolar planets yet: one with 80% of Saturn's mass, orbiting HD46375, and one with 70% of Saturn's mass, orbiting 79 Ceti. These are the first extrasolar planets discovered with masses less than that of Jupiter. Both are, however, quite close to their parent stars; the HD46375 planet has a period of 3 days, while the 79 Ceti planet has a period of 75 days. CNN has coverage. "

Comments

We don't have capacity to detect sol-like systems

[Bob Kopp]

Although it is true we are detecting an awful lot of planetary systems that different from our own -- in particular, ones with gas giants in small, eccentric orbits -- we don't yet have the capacity to detect planetary systems like our own.

There are two boundary conditions on what we can detect: the size of the planets and the distance of their orbit from the star. This is because we can detect planets by noting how much their presence causes their parent star to move. At present, we can detect Saturn-class planets with periods of a couple of years or less. With ground based technology, we may eventually be able to detect Neptune-class planets and planets in Jupiter-like orbits. To detect terrestrial planets, we'll need orbital or lunar telescopes designed for planet searching.

Bob Kopp