This week the Kepler mission confirmed its First Planet in Habitable Zone of a Sun-like Star, they increased the number of planet candidates to 2365, they celebrated 1000 days in space and finally held their first science conference. Today we take a look at the Kepler mission and what it has discovered so far.
The Kepler mission was launched on 6th March 2009, once in orbit and after complete a series of validation tests began scientific observations. Unlike other missions, which look at different regions of the sky based on requests, the Kepler mission is pointing at a single region of sky observing the light from 100,000 stars. Kepler is looking for signs of transiting planets which cause the brightness of the star to change very minutely. Once detected it is possible to determine the orbital size of the planet based on how long the change is observed. To be sure that the observations are correct Kepler needs to see at least three transit which is why it is pointing at the same point most of the time.
Why most of the time? Kepler has to point back to earth once a month to transmit the data it has capture, during this time it cannot observe the stars. Personally I think this is a design flaw and I hope a successor to Kepler will address this.
Why are they Planet Candidates? Kepler can only detect the changes in light from a star, therefore once a change has been detected and verified it needs to be confirmed. Working with different teams around the work they are able to use the other telescopes to actually observe the stars to determine what is really there.
What has Kepler found so far? Of the 2365 candidates announced so far 31 planets have been confirmed orbiting in 22 systems. Included in these is the first known planet to orbit around a binary star system (Kepler 16b), the first near earth sized planet detected in habitual zone of the star (Kepler 22b). Kepler is now starting to see planets that have longer orbital periods, most of the early candidates all have very short periods but the recently annouced Kepler 22b has a 290 day orbit.
What does the future hold? Kepler has been designed to operate for at least 3.5 years, assuming there are no problems the craft will hopefully continue to operate long after that and provide further lots more candidates with longer orbital periods.
Is that all the planets? No Kepler is only observing one region of the sky and focused on 100,000 stars, it is only able to detect the change in brightness caused by a planet transiting the star.
First this is a very very very small percentage of the known stars in the universe, estimated to be 300,000,000,000,000,000,000,000, or 300 sextillion. So far in 1,000 days of obervation we have detected 2365 candidates from the 100,000 stars (0.02365%). If we use the same percentage of the estimate there could be as many as 7,000,000,000,000,000,000,000 or 7 sextillion planets in the universe.
Second Kepler can only see the planets that move directly in front of the star from our line of sight. We know for a fact from other observations using other methods that there are exoplanets that Kepler cannot see, therefore we could conclude from this that each known method could have the same number of candidates in the universe. This continue to increase as Kepler finds more candidates.
What’s next? The next big observatory that is planned to be launched is the James Webb Space Telescope which will have the power to see some of these planet candidates and allow us to really see the finer details of these planets. At present there is no details of a planned follow up to Kepler but hopefully the number of candidates already returned will encourage NASA to look into one.