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Kepler-21b discovery
11.30.2011

See published paper: Kepler-21b: A 1.6REarth Planet Transiting the Bright Oscillating F Subgiant Star HD 179070.

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The Kepler field as seen in the sky over Kitt Peak National Observatory. The approximate position of Kepler-21 is indicated by the circle. See NOAO press release>. Credit: sky imaged using a diffraction grating to show spectra of brighter stars ( J. Glaspey); telescopes imaged separately and combined (P. Marenfeld).
See Press Release from National Optical Astronomical Observatory NOAO: New Planet Kepler-21b discovery a partnership of both space and ground-based observations (RELEASE NO: NOAO 11-08)

Excerpt:
...[Kepler] now has another planet to add to its growing list. A research team led by Steve Howell, NASA Ames Research Center, has shown that one of the brightest stars in the Kepler star field has a planet with a radius only 1.6 that of the earth’s radius and a mass no greater that 10 earth masses, circling its parent star with a 2.8 day period. With such a short period, and such a bright star, the team of over 65 astronomers (that included David Silva, Ken Mighell and Mark Everett of NOAO) needed multiple telescopes on the ground to support and confirm their Kepler observations. These included the 4 meter Mayall telescope and the WIYN telescope at Kitt Peak National Observatory. The accompanying figure shows the size of the Kepler field, seen over Kitt Peak.


With a period of only 2.8 days, this planet, designated Kepler-21b, is only about 6 million km away from its parent star. By comparison Mercury, the closest planet to the sun, has a period of 88 days and a distance from the sun almost ten times greater, or 57 million km. So Kepler 21b is far hotter than any place humans could venture. The team calculates that the temperature at the surface of the planet is about 1900 K, or 2960 F.


...The parent star, HD 179070, is quite similar to our sun: its mass is 1.3 solar masses, its radius is 1.9 solar radii, and its age, based on stellar models, is 2.84 billion years (or a bit younger than the sun’s 4.6 billion years). ...While it cannot be seen by the unaided eye, a small telescope can easily pick it out....

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