Notable among these is the announcements of more ‘super-Earths’.
The planet HD 40307g is the most distant from its sun of six planets found in its system, and takes 200 days to orbits its star. At seven times Earth-mass, bets are on as to whether this planet is rocky or a Neptune-like world. Astronomers put it at about 50:50. The system is around 42 lightyears away. Not only does it orbit in a habitable zone, the target system is also close enough to potentially image directly in the future using the next generation of space-based telescopes. Bring it on!
Gilese 163c is another planet in its stars habitable zone, also estimated at seven times the mass of the Earth. The planet orbits a red dwarf slightly dimmer than old Sol and zips around it in 26 days [red dwarfs are the most common star type in the Milky Way].
Other discoveries showed planets where you least expect to find them – in multiple star systems. Solving multiple-body problems like that give even the most brilliant mathematicians a severe headache. But that does not stop us from seeing what’s out there.
The gas giant PH1orbits a pair of stars that are part of a four-star system [in this case it would orbit the centre of mass of the two stars]. The first planet found in a four-star system. It is bigger than Neptune, and easily big enough to host rocky moons approaching Earth-size. Unfortunately its location makes it too hot for liquid water – its temperature is estimated to range between 251C to 340C (484-644F).
The best thing about PH1 is that it was discovered by two amateur astronomers as part of the Planet Hunters program. So non-professionals get to play too!
A number of binary systems with planets have now been found, some with planets near the habitable zone, such as Kepler-34b and Kepler 35b. Each would get that double-star sunrise, just like Tatooine. Both planets are big, and around 5000 lightyears from Earth. So no exploring just yet.
As for the closest planet, that is a rocky planet orbiting Alpha Centauri B, 4.2 lightyears from Earth. No need to pack the swimsuit – unless you like doing laps in lava. It orbits its sun in a little over 3 days at a distance one tenth of Mercury’s orbit. Ouch.
What were your favourite discoveries of the year?
Cross-posted at chrismcmahons blog.