HD 219134 c

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HD 219134 c
Discovery
Discovery site HARPS-N of the Telescopio Nazionale Galileo
Discovery date2015 July 30
radial velocity method (HARPS-N);
Orbital characteristics
Apastron 0.06935 (± 0.00588) AU
Periastron 0.06125 (± 0.00588) AU
0.06530 (± 0.0008) [1] AU
Eccentricity 0.062 (± 0.039) [1]
6.76458 (± 0.00033) [1] d
Inclination 87.28 (± 0.1) [1]
Star HD 219134
Physical characteristics
Mean radius
1.511 (± 0.047) [2] R🜨
Mass 4.36 (± 0.22) [2] MEarth
Mean density
6.969 +1.08
−0.933 g cm−3
1.91 +0.23
−0.20 g
Temperature 782 K (509 °C; 948 °F) [2]

    HD 219134 c, also known as HR 8832 c, is a hot, dense, rocky exoplanet orbiting around the K-type star HD 219134 in the constellation of Cassiopeia. Originally thought to be a little less than three times the mass of Earth, it is now known to be over 4 times the mass and 51% larger in radius, suggesting a rocky composition with a higher quantity of iron than Earth. The exoplanet was initially detected by the instrument HARPS-N of the Italian Telescopio Nazionale Galileo via the radial velocity method. Transits of the planet were observed by the Spitzer Space Telescope in 2017. Later that year, it was predicted that HD 219134 c has an atmosphere.

    Contents

    Characteristics

    Mass, radius, and temperature

    HD 219134 c is confirmed to be a rocky super-Earth, meaning that it has a solid surface but is significantly larger than Earth. The mass of the planet has been determined to be around 4.36 MEarth with very low uncertainty. Its radius was found to be 1.511 R🜨 (9,627 km), once again with a small error margin. Despite being smaller in both mass and radius than its sister planet, HD 219134 c's density works out to be higher, at almost 7 g/cm3, heavily implying a rock and iron based composition, similar to the terrestrial planets in the Solar System. However, it appears to have a somewhat higher fraction of iron than Earth. The planet's gravitational pull is around 1.91g, or over 90% greater than that of Earth. [3]

    Based on the planet's close proximity to the star, HD 219134 c is much hotter than Earth. It receives about 62 times the incident flux of Earth, and has an equilibrium temperature of 782 K (509 °C; 948 °F), hot enough to melt certain metals. [3] Depending on the greenhouse effect and/or the amount of cloud cover in the planet's atmosphere, its actual temperature may be significantly higher or lower.

    Orbit and rotation

    HD 219134 c orbits its host star very closely, taking just 6.76 days to complete one full revolution at an orbital radius of 0.0653 AU. For comparison, the planet Mercury takes almost 88 days to orbit at a distance of 0.38 AU. Due to its close proximity to the star, the planet is likely a synchronous rotator, where one side of the planet always faces the parent star. HD 219134 c is near a 9:5 resonance with HD 219134 b and a 3:1 resonance with HD 219134 f.

    Host star

    The planet orbits a (K-type) star named HD 219134, orbited by a total of five to seven planets. The star has a mass of 0.81 M☉ and a radius of 0.778 R☉. It has a temperature of 4699 K and is about 11.0 billion years old, making it one of the oldest stars. In comparison, the Sun is 4.6 billion years old [4] and has a temperature of 5778 K. [5]

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

    Atmosphere

    In 2017, it was predicted that HD 219134 c and HD 219134 b likely have atmospheres that are secondary in nature, based on the compositions of the planets and the potential for atmospheric escape. For HD 219134 c, the predicted atmosphere was calculated to reach a height of about 0.13 R🜨 (~830 km), below the predicted height of a primordial hydrogen atmosphere (0.19 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 HD 219134 c lacks the amount of volatiles of its sister planet and has an atmosphere more similar to the terrestrial planets of the Solar System. This planet may had liquid water when it formed but unfortunately it was too close to its host star thus may had suffered an runaway greenhouse effect and is a Venus a-like world. [6]

    Related Research Articles

    <span class="mw-page-title-main">HD 219134</span> Star in the constellation Cassiopeia

    HD 219134 is a main-sequence star in the constellation of Cassiopeia. It is smaller and less luminous than the Sun, with a spectral class of K3V, which makes it an orange-hued star. HD 219134 is relatively close to our system, with an estimated distance of 21.34 light years. This star is close to the limit of apparent magnitude that can still be seen by the unaided eye. The limit is considered to be magnitude 6 for most observers. This star has a magnitude 9.4 optical companion at an angular separation of 106.6 arcseconds.

    <span class="mw-page-title-main">Super-Earth</span> Planet with a mass between Earth and Uranus

    A Super-Earth is a type of exoplanet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, although "mini-Neptunes" is a more common term.

    <span class="mw-page-title-main">HD 85512 b</span> Terrestrial exoplanet orbiting HD 85512

    HD 85512 b is a currently-disputed exoplanet orbiting HD 85512, a K-type main-sequence star approximately 37 light-years from Earth in the constellation of Vela.

    <span class="mw-page-title-main">Kepler-62e</span> Habitable-zone super-Earth planet orbiting Kepler-62

    Kepler-62e is a super-Earth exoplanet discovered orbiting within the habitable zone of Kepler-62, the second outermost of five such planets discovered by NASA's Kepler spacecraft. Kepler-62e is located about 990 light-years from Earth in the constellation of Lyra. The exoplanet was found using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. Kepler-62e may be a terrestrial or ocean-covered planet; it lies in the inner part of its host star's habitable zone.

    Kepler-62b is the innermost and the second smallest discovered exoplanet orbiting the star Kepler-62, with a diameter roughly 30% larger than Earth. It was found using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. It is likely to have an equilibrium temperature slightly higher than the surface temperature of Venus, high enough to melt some types of metal. Its stellar flux is 70 ± 9 times Earth's.

    <span class="mw-page-title-main">HD 219134 b</span> Super-Earth orbiting HD 219134

    HD 219134 b is one of at least five exoplanets orbiting HD 219134, a main-sequence star in the constellation of Cassiopeia. 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. 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. The exoplanet has a mass of about 4.5 times that of Earth and orbits its host star every three days. In 2017, it was found that the planet likely hosts an atmosphere.

    Kepler-283c is an exoplanet orbiting the K-type star Kepler-283 every 93 days in the circumstellar habitable zone, discovered by the Kepler space telescope in 2014.

    HD 219134 f, also known as HR 8832 f, is an exoplanet orbiting around the K-type star HD 219134 in the constellation of Cassiopeia. It is a Super-Earth with a minimum mass of over 7 times that of Earth. Unlike HD 219134 b and HD 219134 c it was not observed by the Spitzer Space Telescope and thus its radius and density are unknown. Only a minimum radius can be given.

    HD 219134 g, also known as HR 8832 g, is an unconfirmed exoplanet orbiting around the K-type star HD 219134 in the constellation of Cassiopeia. It has a minimum mass of 11 or 15 Earth masses, suggesting that it is likely a Neptune-like ice giant. Unlike HD 219134 b and HD 219134 c it is not observed to transit and thus its radius and density are unknown. If it has an Earth-like composition, it would have a radius 1.9 times that of Earth. However, since it is probably a Neptune-like planet, it is likely larger.

    <span class="mw-page-title-main">TRAPPIST-1c</span> Rocky exoplanet orbiting TRAPPIST-1

    TRAPPIST-1c, also designated as 2MASS J23062928-0502285 c, is a mainly rocky exoplanet orbiting around the ultracool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation Aquarius. It is the third most massive and third largest planet of the system, with about 131% the mass and 110% the radius of Earth. Its density indicates a primarily rocky composition, and observations by the James Webb Space Telescope announced in 2023 suggests against a thick CO2 atmosphere, however this does not exclude a thick abiotic oxygen-dominated atmosphere as is hypothesized to be common around red dwarf stars.

    <span class="mw-page-title-main">TRAPPIST-1f</span> Earth-size exoplanet orbiting TRAPPIST-1

    TRAPPIST-1f, also designated as 2MASS J23062928-0502285 f, is an exoplanet, likely rocky, orbiting within the habitable zone around the ultracool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation of Aquarius. The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured.

    <span class="mw-page-title-main">TRAPPIST-1e</span> Earth-size exoplanet orbiting TRAPPIST-1

    TRAPPIST-1e, also designated as 2MASS J23062928-0502285 e, is a rocky, close-to-Earth-sized exoplanet orbiting within the habitable zone around the ultracool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation of Aquarius. Astronomers used the transit method to find the exoplanet, a method that measures the dimming of a star when a planet crosses in front of it.

    <span class="mw-page-title-main">Ross 128 b</span> Confirmed terrestrial exoplanet orbiting Ross 128

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    WASP-47 is a star similar in size and brightness to the Sun about 870 light-years away in the constellation Aquarius. It lies within the Kepler K2 campaign field 3. It was first noticed to have a hot Jupiter exoplanet orbiting every 4 days in 2012 by the Wide Angle Search for Planets (WASP) team. While it was thought to be a typical hot Jupiter system, three more planets were found in 2015: an outer gas giant within the habitable zone, a hot Neptune exterior to the hot Jupiter's orbit and a super-Earth interior to the hot Jupiter's orbit. WASP-47 is the only planetary system known to have both planets near the hot Jupiter and another planet much further out.

    K2-141b is a massive rocky exoplanet orbiting extremely close to an orange main-sequence star K2-141. The planet was first discovered by the Kepler space telescope during its K2 “Second Light” mission and later observed by the HARPS-N spectrograph. It is classified as an Ultra-short Period (USP) and is confirmed to be terrestrial in nature. Its high density implies a massive iron core taking up between 30% and 50% of the planet's total mass.

    <span class="mw-page-title-main">KOI-4878.01</span> Extrasolar planet

    KOI-4878.01 is an exoplanet candidate that orbits the F-type main-sequence star KOI-4878. It is located about 1075 light years from Earth. The features of the planet are very similar to that of Earth, and if it is confirmed, it would be one of the most Earth-like planets found. The orbital period of the exoplanet is around 449 Earth days. It is very likely located within the habitable zone of its parent star.

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    <span class="mw-page-title-main">BD+60 1417b</span> Exoplanet

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    <span class="mw-page-title-main">K2-332 b</span> Potentially habitable exoplanet

    K2-332 b is a potentially habitable Super-Earth or Mini-Neptune exoplanet with a radius of 2.2 earths. It is in the empirical habitable zone, receiving 1.17 times the light that Earth gets from the sun. Its star, K2-332, is type M4V, with a temperature of ~3300 K. It was detected using the transit method in 2016 and is 402 light-years away.

    References

    1. 1 2 3 4 "HD 219134 c". exoplanetarchive.ipac.caltech.edu. Retrieved 2017-12-24.
    2. 1 2 3 "HD 219134". exoplanetarchive.ipac.caltech.edu. Retrieved 2017-12-26.
    3. 1 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 . Bibcode:2017NatAs...1E..56G. doi:10.1038/s41550-017-0056. S2CID   56075932.
    4. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today . Retrieved 19 February 2011.
    5. ↑ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
    6. ↑ Dorn, Caroline; Heng, Kevin (2018). "Secondary Atmospheres on HD 219134 b and C". The Astrophysical Journal. 853 (1): 64. arXiv: 1711.07745 . Bibcode:2018ApJ...853...64D. doi: 10.3847/1538-4357/aa9c80 . S2CID   59377397.
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