HD 219134 b

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HD 219134 b (or HR 8832 b) is one of seven exoplanets orbiting HR 8832, a main-sequence star in the constellation of Cassiopeia.^[1]^[2]^[3]^[4] As of July 2015, super-Earth HD 219134 b, with a size of about 1.6 Earth Radii, and a density of 6g/cm³, was reported as the closest rocky exoplanet to the Earth, at 21.25 light-years away.^[1] The exoplanet was initially detected by the instrument HARPS-N of the Italian Telescopio Nazionale Galileo via the radial velocity method and subsequently observed by the Spitzer telescope as transiting in front of its star.^[1]^[3] The exoplanet has a mass of about 4.5 times that of Earth and orbits its host star every three days.^[1]

Characteristics

Mass, radius and temperature

HD 219134 b is a super-Earth, an exoplanet with a radius and mass bigger than Earth, but smaller than that of the ice giants Neptune and Uranus. Its surface temperature is around 800 K (527 °C; 980 °F). It has a radius of 1.6 R_🜨 and a mass of around 4.5 M_E.

Host star

The planet orbits a (K-type) star named HR 8832, orbited by a total of seven planets. The star has a mass of 0.79 M_☉ and a radius of 0.80 R_☉. It has a temperature of 4710 K and is about 12.5 billion years old, making it one of the oldest stars. In comparison, the Sun is 4.6 billion years old^[5] and has a temperature of 5778 K.^[6]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 5. It can be seen with the naked eye.

Orbit

HD 219134 b orbits its host star with about 28% of the Sun's luminosity with an orbital period of 3 days and an orbital radius of about 0.03 times that of Earth's (compared to the distance of Mercury from the Sun, which is about 0.38 AU).

Gallery

Exoplanet HD 219134 b

Star HR 8832 (circled) lies just off the "W" shape of the constellation Cassiopeia.

Zooming in on the exoplanet
(00:53; animation; July 30, 2015).

References

^ ^a ^b ^c ^d Chou, Felicia; Clavin, Whitney (30 July 2015). "NASA's Spitzer Confirms Closest Rocky Exoplanet". NASA. Retrieved 31 July 2015.
^ Cite error: The named reference harps39 was invoked but never defined (see the help page).
^ ^a ^b "PIA19832: Location of Nearest Rocky Exoplanet Known". NASA. 30 July 2015. Retrieved 30 July 2015.
^ PLANET HOST OVERVIEW PAGE
^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
^ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.

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