The Kepler Space Mission: Well Outside the Bubble

The Kepler spacecraft

The Kepler mission, named after the German astronomer Johannes Kepler, began in 2009. The Kepler spacecraft was successfully launched in March 2009 and has been sending information from its telescope since June of that year. The main purpose of this mission is to detect extrasolar planets (planets outside of our solar system). The Kepler telescope achieves this by continuously monitoring the light from almost 150,000 stars. The data collected from measuring any fluctuations in their brightness enables the detection of planets moving across the face of the stars.

The project had been dogged by cutbacks and funding problems but has already provided a series of fascinating discoveries. In February of this year the discovery of a six planet system was announced. The startling thing about this system though, is how compact it is: the system has ten times the mass of Earth contained within the radius of Mercury’s orbit (0.4 Astronomical unit). To compare, there is only twice the mass of Earth within radius of Mars’ orbit (~4 AU). Never before had scientists who model the behaviour of planet formation thought such a system of planets could exist. This system is located 2000 light years away and is circling a eight billion year old star.

Also in February this year, it was revealed just how many potential exoplanets that the Kepler spacecraft has detected already – over 1200. These planets come in a large range of sizes. Sixty-eight earth-size planets have been detected, as well as 288 super-Earths, which are up to twice the size of the Earth. To put this into some context, the area of the sky that this telescope is constantly observing is only 1/400th. Therefore, if so many planets have already been found in such a small amount of space so quickly, it is difficulty to imagine the actual quantity of planets in the observable sky, let alone beyond that.

The Milky Way showing the fraction of the galaxy that the telescope is observing

One of the latest discoveries by the telescope has been of a three-star system. The trio consists of a red giant and two binary stars. What’s happening in the system has be deduced by measuring the tiny amount of light variations as the stars move. However, the most intriguing detail of this system is the lack of sound. Normally, due to large pressure changes in the stars inner workings the stars normally emit massive pressure waves, essentially sound waves at very low frequencies. But this system, which should generate large noise levels due to the presence of three stars, emits very little. The initial theories suggest that the precise movement of these stars dampens the pressure waves at exactly the right time to make it seem like there is very little sound being emitted. The other theory is that due to differences in the inner workings of these stars they do not pulsate in the manner normally observed.

From these examples, it is evident just how much the Kepler mission has discovered after only two years in operation. And if its record so far is anything to go by, there are going to be many more discoveries by the telescope. These discoveries will not only help scientists refine theories about such phenomena as star and planet formation but also to develop new ones.

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