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Talk:Kepler-47

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examiner.com/article/the-nature-of-the-kepler-47-system

http://www.openexoplanetcatalogue.com/system.html?id=Kepler-47(AB)%20b

On Wednesday, astronomers announced the discovery of two planets orbiting a binary star system known as Kepler-47. The star is 1,500 parsecs away from Earth, and is the first binary star system that has been found to have more than one planet. The two planets were discovered by NASA's Kepler space telescope, which has spotted 77 exoplanets and 2,321 exoplanet candidates since it was launched in March 2009.

Kepler-47 is in the constellation Cygnus. The two stars are known as Kepler-47A and Kepler-47B, and they orbit each other every 7.45 Earth days.

Kepler-47A has 1.043±0.055 times the mass of the Sun and 0.964±0.017 times the radius of the Sun. Its mean surface temperature is estimated to be 5636±100 K, while the mean surface temperature of the Sun is 5778 K. The spectral classification of Kepler-47A is G6V, which is slightly dimmer and redder than the G2V spectral classification of the Sun.

Kepler-47B has 0.362±0.013 times the mass of the Sun and 0.3506±0.0063 times the radius of the Sun. Its mean surface temperature is estimated to be 3357±100 K. The spectral classification of Kepler-47B is M4V, making it a red dwarf star.

• Obviously the irradiance is unreferenced, but the formula is basic:
  

=((((695500000)*0.964)^2)*(0.0000000567051)*(5636^4))/(149597870690*0.989)^2 = 13152.09 W/m²

24.79.40.8 (talk) 22:47, 10 September 2013 (UTC)[reply]

Lede states there are "at least three planets" then goes on to talk about "the two planets". Inconsistency is obvious. Qemist (talk) 06:31, 26 April 2014 (UTC)[reply]

• The discovery paper has an orphan transit, which Kratter & Shannon 2014 identify as a planet to be published by Orosz et al. shortly (and it's been discussed at conferences and the like). WilyD 17:04, 27 August 2014 (UTC)[reply]

Why is the surface gravity of Kepler-47B bigger than that of Kepler-47A, while the former is less massive? Aminabzz (talk) 17:34, 12 May 2023 (UTC)[reply]

Because star B is significantly more dense than star A. SevenSpheres (talk) 19:37, 12 May 2023 (UTC)[reply]

Newton himself gave us a formula for gravity and it just has mass and distance. Volume and density are irrelevant. Aminabzz (talk) 22:10, 18 May 2023 (UTC)[reply]

This is specifically the surface gravity. Kepler-47A indeed has a greater gravitational force on an object at a given distance from it than Kepler-47B has on an object at the same distance, but since Kepler-47A is larger, its surface is farther from its center of mass and so the gravity at its surface is (slightly) less than that of Kepler-47B. SevenSpheres (talk) 21:58, 20 May 2023 (UTC)[reply]