It's only the start of February, but already this year the Extrasolar Planets Encyclopedia has added six new planets.

There are pictures of fewer than two dozen planets orbiting stars outside the Solar System. But astronomers have discovered nearly nine hundred of them. Ever wonder how they find what they can't see? See Searching for Extrasolar Planets.

You can help in the search for extrasolar planets.

PlanetHunters

It's part of the Zooniverse citizen science project. You need to register to take part, but you can try out the tutorial and look through the guide, etc. without doing that. People are looking at data from the Kepler mission to search out patterns that suggest a planet is transiting (going in front of) a star.

Citizen scientists taking part in the PlanetHunters project found a planet in October 2012 from studying the data from NASA's Kepler mission. It’s been named PH1 and it orbits a double star which is also orbited by another pair of stars at about 900 times the Earth-Sun distance. PH1 is somewhat larger than Neptune and orbits every 137 days.

I'm a bit behind on new planets. The Planet Hunters project discovered a second confirmed planet last mongth - so there's now a PH2. It's in the habitable zone of its star, but is a gas planet like Jupiter so not likely to have life on it.

Planet Hunters have also found 31 good planet candidates, but there needs to be more data to confirm them.

If you want to join in the search, the website is Planet Hunters. I've been having a go, but I haven't seen anything that looks even vaguely promising. But you never know!

In May a reaction wheel failed on the Kepler spacecraft. It needs three to position itself precisely in three dimensions but that left it with only two. It had a spare, but that was already in use after a previous failure.

The analysis of the data goes on because there is LOTS of it, but also NASA engineers haven't been idle. Since the optics are still ok, yesterday they began a set of tests to try to see if they could get one of the two failed reaction wheels working again. The tests are set to continue for about a week and they should tell us whether there's some hope of recovering Kepler.

The tests on the Kepler spacecraft's reaction wheels have had some success. There is movement in both of them. At least one of them needs to be working in order to point the spacecraft accurately enough to make its precision observations.

BUT the big test is yet to come. The wheels need to move smoothly, so the critical test is to see how much friction they are generating.

NASA has announced, "Following months of analysis and testing, the Kepler Space Telescope team is ending its attempts to restore the spacecraft to full working order, and now is considering what new science research it can carry out in its current condition."

The loss of the reaction wheels mean that the spacecraft can't be positioned accurately enough for its planet-hunting task. However so far the optics are still in good working order. So there may be a further use for Kepler.

Recently-discovered Kepler-78b is a planet of boiling lava which is so close to its star that it has a surface temperature of 7400 degrees C (over 13,000 degrees F). Artistic impression of a planet like Kepler-78b

Here is the light curve of star Kepler 78. It shows how there is a slight dip in the amount of light as the planet transits (crosses in front of) its star.

You can learn more here about finding extrasolar planets.

Why would the Kepler spacecraft need three gyros to position itself properly? Here is a great infographic that explains the pointing precision it needs for its measurements by taking you into a movie theater and using that scale: A Matter of Scale

It comes down to keeping a grain of salt on the popcorn in view at a distance of a quarter of a mile!

NASA asked for proposals for science that could be done with the Kepler spacecraft. They got 42 papers and are now assessing them for scientific value, how well they match Kepler's capability, and of course, cost. So there might be a new mission for what has been a superb instrument.

If you want to find out more about about the man whose name the spacecraft bears, here's a link to Johannes Kepler - His Life.

Currently, the Kepler spacecraft can't collect data, but it's already made observations on 150,000 stars with 21 million light curves. (The light curves show the light from a star – if there are planets moving in front of it, there will be occasional dips in the light.)

The data has come in faster than it can be analyzed, but there has been an update this month. There are now over 3500 exoplanet candidates, though not all of these will turn out to be planets. Interestingly, there was a big increase in the number of smaller candidates in the Earth-sized range. Here is a graph of the current tally of planet candidate sizes.