HD 219134 b
Coordinates: 23h 13m 16.98s, +57° 10′ 06.1″
HD 219134 b (or HR 8832 b) is one of at least five exoplanets
orbiting HD 219134, a main-sequence star in the constellation of
HD 219134 b
Cassiopeia.[3][1][4][5] HD 219134 b has a size of about 1.6 R🜨,
and a density of 6.4 g/cm3 and orbits at 21.25 light-years away.[3]
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.[3][4] The exoplanet has a mass of
about 4.5 times that of Earth and orbits its host star every three An artist's impression of the hot
days.[3] In 2017, it was found that the planet likely hosts an rocky exoplanet HD 219134 b.
atmosphere.
Discovery
Discovery site HARPS-N of the
Characteristics Telescopio
Nazionale Galileo
Mass, radius and temperature Discovery date 30 July 2015
Detection radial velocity
HD 219134 b is a super-Earth, an exoplanet with a radius and method method (HARPS-
mass bigger than Earth, but smaller than that of the ice giants N)
Neptune and Uranus. Using both the radial velocity and transit
method, both its mass and radius have been well determined, Orbital characteristics
allowing for accurate modelling of the planet's composition. HD Semi-major 0.038764 (±
219134 b has a radius of 1.602 R🜨 and a mass of 4.74 MEarth , axis 0.0047)[1] AU
giving it a density of about 6.4 g/cm3 and 1.85 times the gravity of Eccentricity 0 (fixed)[1]
Earth. This is consistent with a rocky, Earth-like composition. This
is relatively unusual, as most planets of ≥1.6 R🜨 are expected to be Orbital period 3.092926 (±
(sidereal) 0.0004)[1] d
rich in volatile materials, such as water and gas. Despite its Earth-
like composition, the planet's equilibrium temperature is around Inclination 85.058 ± 0.08[1]
1,015 K (742 °C; 1,367 °F), far too hot for liquid water or life.
Star HD 219134
Depending on the amount of cloud cover in the atmosphere of HD
219134 b, the actual temperature may be somewhat lower, but Physical characteristics
nowhere near the range for liquid water. Mean radius 1.602 ± 0.055[2]
R🜨
Host star Mass 4.74 (± 0.19)[1]
MEarth
The planet orbits a (K-type) star named HD 219134, orbited by a Mean density 6.36 (± 0.72)[1] g
total of five to seven planets. The star has a mass of 0.81 M☉ and a cm−3
radius of 0.778 R☉ . It has a temperature of 4699 K and is about
Surface gravity 1.847 +0.213 g
11.0 billion years old, making it one of the oldest stars. In −0.19
comparison, the Sun is 4.6 billion years old[6] and has a Temperature 1,015 K (742 °C;
temperature of 5778 K.[7] 1,367 °F)
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
0:00
HD 219134 b orbits its host star with about 28% of the
Sun's luminosity with an orbital period of 3 days and
Zooming in on the exoplanet HD 219134 b an orbital radius of about 0.03 times that of Earth's
(00:53; animation; 30 July 2015). (compared to the distance of Mercury from the Sun,
which is about 0.38 AU).
Atmosphere
In 2017, it was predicted that HD 219134 b and HD 219134 c likely have atmospheres that are secondary
in nature, based on the compositions of the planets and the potential for atmospheric escape. For HD
219134 b, the predicted atmosphere was calculated to reach a height of about 0.18 R🜨 (~1,150 km), below
the predicted height of a primordial hydrogen atmosphere (0.28 R🜨). This would indicate a secondary
atmosphere produced by processes like volcanic activity and evaporation of volatile materials. However,
the composition of volatile materials on HD 219134 b and c could not be accurately determined, yet it is
believed that the former has a very thin gaseous envelope, far thinner than those of Uranus and Neptune.[8]
See also
List of exoplanet extremes
Other rocky planets with confirmed atmospheres:
TRAPPIST-1b and TRAPPIST-1c
Gliese 1132 b, has an atmosphere rich in water and methane.
55 Cancri e, has an atmosphere with hydrogen, helium, hydrogen cyanide, nitrogen,
and/or carbon monoxide.
References
1. Motalebi, F.; et al. (2015). "The HARPS-N Rocky Planet Search, I. HD 219134b: A transiting
rocky planet in a multi-planet system at 6.5 pc from the Sun" (http://pure.qub.ac.uk/portal/file
s/48391151/he_HARPS_N_Rocky_Planet_Search.pdf) (PDF). Astronomy & Astrophysics.
584: A72. arXiv:1507.08532 (https://arxiv.org/abs/1507.08532).
Bibcode:2015A&A...584A..72M (https://ui.adsabs.harvard.edu/abs/2015A&A...584A..72M).
doi:10.1051/0004-6361/201526822 (https://doi.org/10.1051%2F0004-6361%2F201526822).
S2CID 45652878 (https://api.semanticscholar.org/CorpusID:45652878).
2. Gillon, Michaël; et al. (2017). "Two massive rocky planets transiting a K-dwarf 6.5 parsecs
away". Nature Astronomy. 1 (3). 0056. arXiv:1703.01430 (https://arxiv.org/abs/1703.01430).
Bibcode:2017NatAs...1E..56G (https://ui.adsabs.harvard.edu/abs/2017NatAs...1E..56G).
doi:10.1038/s41550-017-0056 (https://doi.org/10.1038%2Fs41550-017-0056).
S2CID 56075932 (https://api.semanticscholar.org/CorpusID:56075932).
3. Chou, Felicia; Clavin, Whitney (30 July 2015). "NASA's Spitzer Confirms Closest Rocky
Exoplanet" (http://www.jpl.nasa.gov/news/news.php?feature=4672). NASA. Retrieved
31 July 2015.
4. "PIA19832: Location of Nearest Rocky Exoplanet Known" (http://photojournal.jpl.nasa.gov/c
atalog/PIA19832). NASA. 30 July 2015. Retrieved 30 July 2015.
5. "HD 219134" (http://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-Display
Overview?objname=HD+219134&type=PLANET_HOST).
exoplanetarchive.ipac.caltech.edu.
6. Fraser Cain (16 September 2008). "How Old is the Sun?" (http://www.universetoday.com/18
237/how-old-is-the-sun/). Universe Today. Retrieved 19 February 2011.
7. Fraser Cain (15 September 2008). "Temperature of the Sun" (http://www.universetoday.com/
18092/temperature-of-the-sun/). Universe Today. Retrieved 19 February 2011.
8. Dorn, Caroline; Heng, Kevin; Gillon, M.; Lovis, C.; Segransan, D.; Buchhave, L. A.; Demory,
B. O.; Malavolta, L.; Dressing, C. D.; Sasselov, D.; Rice, K.; Charbonneau, D.; Collier
Cameron, A.; Latham, D.; Molinari, E.; Pepe, F.; Affer, L.; Bonomo, A. S.; Cosentino, R.;
Dumusque, X.; Figueira, P.; Fiorenzano, A. F. M.; Gettel, S.; Harutyunyan, A.; Haywood, R.
D.; Johnson, J.; Lopez, E.; Lopez-Morales, M.; Mayor, M.; et al. (2018). "Secondary
Atmospheres on HD 219134 b and C". The Astrophysical Journal. 853 (1): 64.
arXiv:1711.07745 (https://arxiv.org/abs/1711.07745). Bibcode:2018ApJ...853...64D (https://u
i.adsabs.harvard.edu/abs/2018ApJ...853...64D). doi:10.3847/1538-4357/aa9c80 (https://doi.
org/10.3847%2F1538-4357%2Faa9c80). S2CID 59377397 (https://api.semanticscholar.org/
CorpusID:59377397).
External links
Cassiopeia Constellation at Constellation Guide (http://www.constellation-guide.com/constel
lation-list/cassiopeia-constellation/)
The Deep Photographic Guide to the Constellations: Cassiopeia (http://www.allthesky.com/c
onstellations/Cassiopeia/)
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