Kepler-11
Kepler -11 is a sun -like star of spectral type G in the constellation Cygnus. The star is located about 2000 light years from Earth and is orbited by at least six exoplanets. The planets have been discovered through analysis of data from the Kepler space telescope in the years 2010/11.
Planetary system
The telescope detects decreases in the brightness of stars through before passing planet ( transit method ). These differences in brightness be in the case of Kepler- 11 between 0.03 % ( Kepler - 11b) and 0.14 % ( Kepler - 11e) and to take between four to nine hours. This drawing is called Gone transit. The transits of planets are strictly periodic.
Five of the six planets of the system orbits with a semimajor axis of about 0.09 to 0.25 AU. This would not be in our solar system within the orbit of Mercury. The orbit of the sixth planet, Kepler - 11g, has a semi-major axis of about 0.46 AU and as befände just outside the orbit of Mercury. Due to the small distance between the inner five planets they influence each other, resulting in irregularities in the intervals between the transits occur. These irregularities lead to conclusions on the masses of the planets involved. For Kepler - 11g, the mass could not be determined in this way, because the planet is too far away from the others and very little interacted. Using computer models, its mass was therefore estimated at roughly less than 300 Earth masses. The masses of the inner planets in each case is a few Earth masses. They are among the smallest of known planets outside our solar system were measured for mass and size.
The densities of the planets provide information about its main components: it is due to the low density of Kepler- 11d and e, and probably also of Kepler -11 f to assume that hydrogen occupies the major part of its volume. In contrast, the atmospheres of Kepler- 11b and -c consist of a hydrogen / helium mixture, water vapor and organic compounds. It is likely that Kepler - 11b and - c in the past used a higher proportion of hydrogen in the atmosphere, but have lost it due to their proximity to the star. The cores of the planets are made of rock and iron.
The planetary system of Kepler- 11 is flatter than our solar system, the orbits of the planets are nearly circular and are almost all in the same plane. The orbital planes of Kepler- 11e and Kepler - 11g are slightly inclined with at least 0.6 ° from each other. The low orbital inclination of the planets to each other and to our direction of observation made it possible to find six exoplanets with Kepler and the transit method. Due to the high number of passing in front of the star planet it is more likely to observe the simultaneous transit of more than one planet. Thus, a three-time transit was observed on 26 August 2010, when Kepler -b,- d and -e were simultaneously before the star.