Kepler Space Telescope
Launched in March, 2009, Kepler (unlike Hubble & Spitzer) was designed solely to search for exoplanets. It does this by looking at a single large portion of the sky and studying only the stars that are present there. Kepler, using the transit method, can then:
- Determine the abundance of Earth-sized and larger planets in or near the habitable zone of a wide variety of stars,
- Determine the distribution of sizes and shapes of the orbits of these planets,
- Estimate how many planets there are in multiple-star systems,
- Determine the variety of orbit sizes and planet reflectivities, sizes, masses, and densities of short-period Giant Planets,
- Identify additional members of each discovered planetary system using other techniques, and
- Determine the properties of those stars that harbour planetary systems.
The image below shows Kepler's field of view. It looks at over 100,000 stars. As discussed in the Detection Methods section, the majority of exoplanets discovered so far are large Hot Jupiter sized planets orbiting close to their parent star. The goal of Kepler is to use the Transit method to detect smaller Earth-sized planets that orbit in or near the 'Habitable Zone'.
Originally designed to be in space for 3.5 years, Kepler's mission was extended to 5 years due to its success. In its time in space, Kepler has identified 2,321 candidate planets, 105 of which have been confirmed.
The Kepler Photometer (click to expand)
Kepler is a single-purpose Schmidt telescope or camera. It is the largest of its kind ever launched into space. The starlight that enters the telescope hits the curved primary mirror (which contains a Schmidt corrector plate at its center of curvature) and is directed at the photometer detector (Kepler's single scientific instrument). The photometer is an array of 42 charge coupled devices (CCDs), each divided into pixels which count and store electrons (which are produced when light hits the CCDs).
When light hits the CCDs, electrons are produced and processed to produce an image. Light from a particular star hits the same CCD for a three month period. After three months, Kepler's orientation is shifted so that, as it continues to look at the same set of stars, light from any given star will hit a new CCD.
The video above displays the multi-exoplanet systems discovered by the Kepler Telescope. The orbit radii and the planet sizes are to scale with respect to themselves, but orbits and planet sizes are different scales in respect with eachother. The colours depict solar system types: the two-planet systems have a yellow, 3-planet systems have a green, 4-planet systems have a light blue, 5-planet systems have a dark blue, and 6-planet systems have a purple outer planet.