Kepler-11

Kepler-11 is a sun-like star of spectral class G in the constellation Swan . The star is located about 2000 light years from Earth and is orbited by at least six exoplanets . The planets were discovered by evaluating data from the Kepler space telescope in 2010/11.

Planetary system

The telescope detects reductions in the brightness of stars due to planets passing in front of them ( transit method ). In the case of Kepler-11, these differences in brightness are between 0.03% (Kepler-11b) and 0.14% (Kepler-11e) and last between four and nine hours. This passing is called transit. The transits of a single planet are strictly periodic.

Five of the six planets in the system have semi-major orbits of about 0.09 to 0.25 AU . This would put them in the orbit of Mercury in our solar system . The orbit of the sixth planet, Kepler-11g, has a semi-major axis of about 0.46 AU and would be located slightly outside of Mercury's orbit. Due to the small distance between the inner five planets, they influence each other, which causes irregularities in the time intervals between the transits. These irregularities allow conclusions to be drawn about the masses of the planets involved. For Kepler-11g, the mass could not be determined this way because the planet is too far from the others and interacted very little. Based on computer models, its mass was therefore roughly estimated at less than 300 Earth masses. The masses of the inner planets are each some earth masses. They are among the smallest of the known planets outside of our solar system for which mass and size have been measured.

The densities of the planets provide information about their main components: due to the low density of Kepler-11d and -e and probably also of Kepler-11-f, it can be assumed that hydrogen takes up the greater part of their volume. The atmospheres of Kepler-11b and -c, on the other hand, consist of a hydrogen / helium mixture, water vapor or organic compounds . It can be assumed that Kepler-11b and -c had larger proportions of hydrogen in the atmosphere in the past, but 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 almost circular and almost all lie in the same plane. The orbital planes of Kepler-11e and Kepler-11g are slightly inclined to each other by at least 0.6 °. The low orbital inclination of the planets to each other and to our direction of observation made it possible to find the six exoplanets with Kepler and the transit method. Due to the high number of planets passing in front of the star, it is more likely to observe the simultaneous transit of more than one planet. A triple transit was observed on August 26, 2010 when Kepler-b, -d and -e were in front of the star at the same time.

planet	Mass (in earth masses)	Radius (in earth radii)	Density (g / cm ³ )	Cycle time (days)	Semi-major axis ( AE )	Orbit inclination ( degree )	Simulation of the orbit
b	4.3 (2.3 - 6.5)	1.97 ± 0.19	3.1 (1.6-5.2)	10.30375	0.091	88.5	[2]
c	13.5 (7.4 - 18.3)	3.15 ± 0.30	2.3 (1.2-3.6)	13.02502	0.106	89	[3]
d	6.1 (4.4 - 9.2)	3.43 ± 0.32	0.9 (0.6-1.4)	22.68719	0.159	89.3	[4]
e	8.4 (6.5 - 10.9)	4.52 ± 0.43	0.5 (0.3-0.7)	31.9959	0.194	88.8	[5]
f	2.3 (1.1 - 4.5)	2.61 ± 0.25	0.7 (0.3-1.4)	46.68876	0.25	89.4	[6]
G	<300	3.66 ± 0.35		118.37774	0.462	89.8	[7]

Individual evidence

literature

Jack J. Lissauer et al. a .: A Closely-Packed System of Low-Mass, Low-Density Planets Transiting Kepler-11 . In: Nature . tape 470 , 2011, ISSN 0028-0836 , p. 53–58 , doi : 10.1038 / nature09760 , arxiv : 1102.0291 .

Web links

NASA press release with presentations and additional links
Size comparison of the Kepler-11 planets
The compositions of the planets from Kepler-11
Kepler 11 animation

[1] Simbad

[space.com_kepler-11-2] Astronomers Find 6-Pack of Planets in Alien Solar System

[nasa.gov-3] New planetary system