New planets mean life may be out there
By Amanda Jermyn

In 2009 NASAís Kepler spacecraft was launched to search for planets outside our solar system. Its space telescope scans the sky for stars that experience periodic dips in brightness, the result of one or more planets passing in front of them. Since its launch Kepler has discovered more than 2,326 potential planets which, if confirmed, would quadruple the prior tally of confirmed exoplanets, as these alien worlds are known. This past December Kepler discovered its first exoplanet in its host starís habitable zone, the range of distance from the star where the temperature is just right for liquid water, and possibly life, to exist. This newfound planet, known as Kepler-22b, is about 600 light years away, orbiting a star similar to our Sun.

One of the many stars flagged by Kepler as having a potential planetary system was a red dwarf known as KOI-961. This red dwarf, a type of small, dim star, was then investigated by a team led by astronomers from the California Institute of Technology using ground-based telescopes at the Palomar and Keck Observatories. In January of this year they were able to confirm discovery of the three smallest planets ever detected outside our solar system, all orbiting KOI-961. The findings will be published in the Astrophysical Journal, with Caltechís Philip Muirhead as lead author. All three newly discovered planets are smaller than Earth, with one the size of Mars (about half the size of Earth) and the others smaller than Venus, or about three quarters the size of Earth. We can infer that these exoplanets have solid, rocky surfaces because they are so small that the only way they could have enough gravity to hold themselves together is if they are balls of rock, like Earth and the other rocky planets of our solar system. Before their discovery only a handful of rocky planets had been found orbiting other stars.

The entire KOI-961 planetary system is remarkably small. With a diameter of one sixth that of our Sun, it is in fact only 70% larger than Jupiter. All the planets takes less than two days to orbit their star, and all are about a hundred times closer to the star than Earth is to the Sun. Because they are so close to their star, all are extremely hot, and are therefore orbiting too close to be considered within the habitable zone. Itís worth noting, however, that these planets were found orbiting a red dwarf, the most common type of star in our Milky Way galaxy. Furthermore, out of the potential planetary systems flagged by Kepler, a relatively small number were red dwarfs. The fact that three rocky planets were found among these, combined with how common red dwarfs are in the Milky Way, suggests that our galaxy may harbor many rocky planets, with a good chance some may be in the habitable zone. With these new discoveries the chances of finding life beyond our solar system are looking up!

Join the Springfield Stars Club on Tuesday, March 27th at 7:30pm at the Springfield Science Museum for a talk by Adam Jermyn, a physics major at the California Institute of Technology. Adam will share his experiences at Caltech and give an update on activities at NASAís Jet Propulsion Laboratory there. A 2011 graduate of Longmeadow High School, Adam has been a Springfield Stars Club member for many years. Refreshments will be served, and the public is welcome free of charge.