Another interesting announcement from NASA today in regards to the search for exoplanets. Using a combination of several ground based telescopes together with the Hubble and Spitzer space telescopes, the team has discovered seven new planets, each of which is roughly Earth sized, and orbiting a star a mere 39 lightyears away from the Earth.
The star at the center of this system is a very small, very cold star which was not observed until last May. It has been named TRAPPIST-1, short for Transiting Planets and Planetesimals Small Telescope, and is an interesting system of planets. The star is estimated to be about 1/12 the mass of our own sun, with a radius smaller than that of Jupiter. 

The system of planets is also quite small, with at least four of these planets orbiting closer to each other than the Earth to either Venus or Mars - our nearest neighbours. An observer standing on one of these planets would be able to watch the other three (or more) crossing the sky at night, looking larger and possibly as bright as our Moon.

The size and potential appearance of the seven planets in the TRAPPIST-1 system, in comparison with the four inner planets from our own solar system. Image courtesy of NASA

Because the star is so small and relatively cold, and since these seven planets orbit close to it, planetary scientists believe that all seven could contain liquid water in the form of lakes or oceans. This makes the system even more interesting, because as I have written before every place on Earth that contains water also contains life. So with seven new planets that are believed to in the so-called goldilocks zone of their star, with perfect temperatures and perhaps chemical composition, it is possible that one of them or all of them could have life on it. And being relatively close to the Earth makes it relatively easy for astronomers and astrobiologists to study. (The SETI team have already searched for a signal from this system, but as yet have not found any positive results.)

 At such a close distance, and with a significant number of warm, Earth sized planets, this system could become very important to the study of planetary formation in the coming years. It is really a great discovery!