HD 63433 c

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HD 63433 c
Discovery
Discovered byMann et al. (THYME)[1]
Discovery date30 April 2020[1]
Transit[2]
Designations
TOI-1726 c, BD+27 1490 c, HIP 38228 c, V377 Geminorum c
Orbital characteristics[1]
0.1448+0.0073
−0.0077 AU
Eccentricity0.21+0.33
−0.14
20.54 days
Inclination89.28°+0.4°
−0.22°
StarHD 63433
Physical characteristics[3]
2.692±0.108 R🜨
Mass15.54±3.86 M🜨
Mean density
4.6±1.3 g/cm3
TemperatureTeq: 540+10
−9[a] — 679+13
−11 K [b]

HD 63433 c (TOI-1726 c) is a mini-Neptune exoplanet orbiting the Sun-like star HD 63433.[4] It is the outermost planet in its planetary system, being located 0.1448 astronomical units (21,660,000 km) from its star, and completing one orbit every 21 days.[1] Despite being the outermost planet in the system, it is still located close to its star, meaning that its temperature is hot, being estimated between 267 and 406 °C.[3] HD 63433 c is about 2.7 times larger than Earth and 15.5 times more massive,[3] but still smaller and less massive than Neptune.[note 1] In 2022, a study showed that its atmosphere, made up of hydrogen, is being evaporated by the strong radiation from its star, causing it to slowly turn into a super-Earth planet.[6][7]

Characteristics

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HD 63433 c is classified as a mini-Neptune planet,[6] a class of planets that are smaller than Neptune but still have an atmosphere of hydrogen and/or helium, just like Neptune.[6] According to theoretical models, its composition is mainly of silicate and water, surrounded by a gaseous envelope that makes up about 2% of the planet.[3] HD 63433 c is 2.7 times larger than Earth, but still 1/3 smaller than the Solar System's ice giants, Neptune and Uranus.[3][note 2] Its mass is about 15.5 M🜨, being situated between the masses of Uranus and Neptune, which are 14.54 and 17.15 M🜨 respectively.[5][8] The density of HD 63433 c is calculated at 4.6 g/cm3,[3] slightly lower than Earth's,[note 3] but higher than the densities of Neptune and Uranus.[note 4] The age of the planet is estimated at 400 million years.[4]

It is the outermost planet in its planetary system, orbiting its star at a distance of 0.145 astronomical units (21,700,000 km), with an orbital period of 21 days.[1] Despite being the outermost planet, its distance is about 37% of Mercury's distance from the Sun,[c] in addition to having a high temperature, estimated between 267 and 406 degrees Celsius.[3][d]

Size comparison
Neptune HD 63433 c
Neptune Exoplanet

The discovery of HD 63433 c, as well as all planets orbiting HD 63433, is part of a project called TESS Hunt for Young and Maturing Exoplanets (THYME), whose objective is to discover transiting exoplanets in stellar associations, moving groups and open clusters.[4][1] It was discovered in 2020 by Mann et al., using the Transiting Exoplanet Survey Satellite (TESS), together with HD 63433 b.[11] Both planets were discovered through the transit method.[11]

Evaporating atmosphere

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In 2022, a study led by Michael Zhang observed two mini-Neptunes from distinct planetary systems: HD 63433 c, using the Hubble Space Telescope, and TOI-560.01, using the W. M. Keck Observatory.[7] This study revealed that the atmospheres of the two planets – made up mainly of hydrogen (HD 63433 c) and helium (TOI-560.01) – are evaporating and transforming them into super-Earths, as the strong radiation of their host stars is slowly stripping away their puffy atmospheres, causing them to escape into space, like a hot air balloon.[7][2] In HD 63433 c in particular, these gases are escaping at a speed of 50 km/s, and forming a gas cocoon 12 times larger than the planet itself.[7]

The same effect was not identified on the sibling planet HD 63433 b, which could indicate that it has already lost its primordial atmosphere.[7]

Host star

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Main article: HD 63433

The host star of HD 63433 c is HD 63433, a G-type main-sequence star that is located 73 light-years from Earth in the constellation Gemini.[4][note 5] The properties of this star, such as its radius (0.912 R☉) and its mass (0.99 M☉) are very similar to those of the Sun, which makes it classified as a Solar analog.[4] The star is part of the Ursa Major moving group, allowing its age to be estimated at 414±23 million years.[4] There are other exoplanets orbiting this star, HD 63433 b, also a mini-Neptune, and HD 63433 d, an Earth-sized planet.[1]

See also

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Notes and references

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  3. ^ a b c d e f g Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  4. ^ a b c d e f Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  5. ^ a b c d Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  6. ^ a b c Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  7. ^ a b c d e Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  8. ^ a b c Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
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  1. ^ Assuming an albedo of 0.6
  2. ^ Assuming an albedo of 0
  3. ^ The distance of Mercury to the Sun is 0.387 AU.[10]
  4. ^ Assuming albedos of 0.6 and 0 respectively.
  1. ^ Neptune is 3.883 times larger than Earth, and 17.15 times more massive.[5]
  2. ^ The radius of Neptune and Uranus are 3.883 R🜨[5] and 4.007 R🜨[8] respectively.
  3. ^ The density of Earth is 5.513 g/cm3.[9]
  4. ^ The densities of Neptune and Uranus are 1.638 g/cm3[5] and 1.27 g/cm3[8] respectively.
  5. ^ Obtained with a right ascension of 07h 49m 55.06s and a declination of 27° 21′ 47.5″[12] on this website.

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