Английская Википедия:HD 63433

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Шаблон:Short description Шаблон:Starbox begin Шаблон:Starbox observe Шаблон:Starbox character Шаблон:Starbox astrometry Шаблон:Starbox detail Шаблон:Starbox catalog Шаблон:Starbox reference Шаблон:Starbox end

HD 63433 (TOI-1726, V377 Geminorum) is a G-type main sequence star located 73 light-years from Earth in the zodiacal constellation Gemini,[1]Шаблон:Efn visually close to the star Pollux.[2] It is classified as a Sun-like star, having a mass 99% similar and a size 91% similar to that of the Sun.[1] However, it is a much younger star, less than one tenth as old with an age of about 400 million years.[1]Шаблон:Efn With an apparent magnitude of 6.9, it is not visible to the naked eye, but can be seen with a small telescope.[3] Based on its kinematic, rotational and lithium abundance properties, it is part of the Ursa Major Moving Group.[1] There are three exoplanets orbiting it, one is classified as an Earth-sized planet, while the two others are mini-Neptunes.[4]

Characteristics

HD 63433 is a Sun-like star, having a radius of Шаблон:Val, a mass of Шаблон:Val, an effective temperature of Шаблон:Val and a spectral type G5V.[1] Its properties are quite similar to those of the Sun, which has a spectral type G2V and a temperature of 5772 K.[5] HD 63433, however, is much younger than the Sun, having an age of 414 million years,[1] just 9% of the solar age of 4.6 billion years.[6]

It is also a variable star, belonging to the class of BY Draconis variables,[7][8] stars which have variations in their luminosity due to their rotation together with sunspots and other chromospheric activities. The brightness of the star varies by 0.05 magnitudes over a period of 6.46 days.[8] It has the variable-star designation V377 Geminorum.[2][8]

With an apparent magnitude of 6.92m,[9] it is below the limit for naked-eye visibility, generally defined as 6.5m,[10] which would mean that this star is not visible to the naked eye, but easily visible using a small telescope[3] or binoculars.[11] Despite being faint, HD 63433 is actually the third-brightest star with transiting exoplanets confirmed by the Transiting Exoplanet Survey Satellite, with only Pi Mensae (5.65m)[12] and HR 858 (6.38m)[13] being brighter.[1][14]

According to stellar kinematics, lithium abundance and stellar rotation, HD 63433 is part of the Ursa Major moving group.[1] It was initially identified as a possible member of this group by Gaidos (1998)[15] and included as a possible member in later analyses, until HD 63433's membership in this moving group was finally confirmed by Mann et al. in 2020.[1] As it is part of this moving group, its age is estimated at Шаблон:Nowrap million years, the same as the group.[1]

It is located in the northern hemisphere, about 73 light-years from the Earth, in the constellation of Gemini.[3] It is visually close to Pollux, the brightest star in the constellation.[2] HD 63433 is predicted to approach within Шаблон:Convert of the Sun in 1.33 million years.[16] That will make it one of the nearest stars to the Sun. Its closest neighbor is the orange dwarf HD 63991, located at a distance of 2.7 light years.[3]

Nearest stars to HD 63433[3]
Name Distance

(light-years)

HD 63991 2.7
LSPM J0801+2342 6.1
HD 68017 9
BD+31 1781 9.1
G 90-52 9.2

Planetary system

The star HD 63433 is orbited by 3 exoplanets, all discovered by the transit method.

The first ones to be discovered, HD 63433 b and HD 63433 c, are mini-Neptunes[17] that were discovered in by Mann et al. in 2020 using the Transiting Exoplanet Survey Satellite.[18] In 2024, an additional planet was discovered, after an analysis of a transit signal detected by TESS. Named HD 63433 d, it is an Earth-sized planet.[19]

According to theoretical models, the compositions of the mini-Neptunes HD 63433 b and c are mostly silicate and water, with no iron dominance, surrounded by a gaseous envelope which, in the case of planet c, makes up around 2% of the planet.[17]

The planetary system of HD 63433 is quite young, at around 400 million years old, it is only 9.13% as old as the Solar System.[4][19]Шаблон:Efn HD 63433 d is also the smallest planet and is less than 500 million years old.

Temperature
comparisons 		Шаблон:Nowrap Шаблон:Nowrap Шаблон:Nowrap
Global equilibrium temperature Шаблон:Nowrap Шаблон:Nowrap Шаблон:Nowrap

Шаблон:OrbitboxPlanet begin Шаблон:Orbitbox planet Шаблон:Orbitbox planet Шаблон:Orbitbox planet Шаблон:Orbitbox end

HD 63433 b

Шаблон:Main article

The middle planet, HD 63433 b, is a mini-Neptune planet that was discovered together with HD 63433 c.[4] HD 63433 b is 2.14 times larger than Earth,[17] but is about 45% smaller than Neptune.Шаблон:Efn The planet has an upper mass limit of Шаблон:Val,[17] which is 21% greater than the mass of Neptune (Шаблон:Val [20]). These values calculate an upper density limit of 13 g/cm3,[17] 2 times greater than that of Earth,Шаблон:Efn and similar to that of the chemical element Mercury. HD 63433 b orbits its parent star at a distance of Шаблон:Convert – about 5 times closer than Mercury is to the Sun – and completes one revolution every 7 days and 3 hours. The relative proximity of its star makes it hot, with an equilibrium temperature between 769 and 967 Kelvin (496 and 694 °C).[17]Шаблон:Efn

HD 63433 b was probably a mini-Neptune that later lost its atmosphere.[21] Some factors, such as the fact that no absorption of Ly-α was detected during its transit, and its mass-loss timescale being shorter than the age of the planetary system, indicate that it has already lost its primordial atmosphere, and could be a rocky planetary core.[21] However, if HD 63433 b were a rocky core, it would need to be unusually massive and, therefore, a water-rich composition in addition to an atmosphere with a high mean molecular weight could explain both the radius and the non-detection of the Lyα.[21]

HD 63433 c

Шаблон:Main articleThe outermost planet, HD 63433 c, is a mini-Neptune planet discovered together with HD 63433 b.[1] It is 2.7 times larger than Earth,[17] but 30% smaller than the Solar System's ice giants, Neptune and Uranus. Being 15.5 times more massive than the Earth,[17] it is more massive than Uranus (Шаблон:Val), but still less massive than Neptune (Шаблон:Val). The density of HD 63433 c calculated at 4.6 g/cm3, slightly lower than that of Earth,[17] but greater than the densities of all gas giants in the Solar System.

Orbiting its star at a distance of Шаблон:Convert in a orbital period of 20 days,[17] it is the outermost planet in its planetary system, but still close to its star, making it a warm planet, with a planetary equilibrium temperature estimated between 267 and 406 °C.[17]Шаблон:Efn

Due to the high radiation received from its star, the atmosphere of HD 63433 c, made up of hydrogen, is slowly being stripped away and escaping from the planet, like a hot air balloon.[22] The hot gas escapes into the space at a velocity of 50 km/s, forming a gas cocoon 12 times larger than the planet itself.[22] As its atmosphere evaporates, HD 63433 c will slowly become a super-Earth planet.[22]

HD 63433 d

Шаблон:Main article HD 63433 d was the last planet to be discovered in the system, 4 years after planets b and c.[4] With a diameter of Шаблон:Val, it is very similar to Earth in size, being only 7% larger, but its mass is currently unknown.[4] It is the innermost planet orbiting HD 63433, having a semi-major axis (mean distance from its star) of Шаблон:Convert and an orbital period of just 4 days.[4] The extreme proximity to its star makes it extremely hot, having a daytime temperature estimated at Шаблон:Convert,[4] Шаблон:Efn hot enough to melt all the minerals present on its surface,[23] as well as being tidally locked, meaning that one half of the planet is always facing towards its star, while the other is always facing away from it.[24][19] The planet also possibly lacks a substantial atmosphere.[4][19][23]

It is believed that the dayside of the planet, always facing its star due to tidal locking, is fully composed of lava due to the high surface temperature,[25][19] in addition to possibly having volcanic activity.[26][27] Meanwhile, the nightside of the planet, which never faces its star, may be the opposite, resembling Pluto with glaciers of frozen nitrogen.[28]

HD 63433 d was discovered in 2024, through an analysis of a transit observation made by the Transiting Exoplanet Survey Satellite (TESS).[19] As two other planets had already been discovered in the system, the transit signals of these objects were removed, thus revealing an additional transit signal that reappeared every 4.2 days.[19][29][4] Further investigation allowed researchers to confirm that this signal was from another orbiting exoplanet, now called HD 63433 d.[19] The discovery was announced on January 10, 2024, in The Astronomical Journal.[24][28]

Scientific importance

The HD 63433 planetary system plays an important role in understanding the evolution of planetary systems in the first billion years after formation.[1][4] As HD 63433 is relatively bright (6.9m) and close (73 ly away), its planets b and c can have their atmospheres characterized by the Hubble Space Telescope and James Webb Space Telescope.[21] This star is also a favorable target for studies of atmospheric mass loss in exoplanets, as it is a young and active star with close-in mini-Neptune planets, in addition to having a negative radial velocity (Шаблон:Val).[21]

See also

Notes and references

  1. ↑ 1,00 1,01 1,02 1,03 1,04 1,05 1,06 1,07 1,08 1,09 1,10 1,11 Шаблон:Cite journal
  2. ↑ 2,0 2,1 2,2 Шаблон:Cite web
  3. ↑ 3,0 3,1 3,2 3,3 3,4 Шаблон:Cite web
  4. ↑ 4,0 4,1 4,2 4,3 4,4 4,5 4,6 4,7 4,8 4,9 Шаблон:Citation
  5. ↑ Шаблон:Cite web
  6. ↑ Шаблон:Cite journal
  7. ↑ Шаблон:Cite journal
  8. ↑ 8,0 8,1 8,2 Шаблон:Cite web
  9. ↑ Шаблон:Cite web
  10. ↑ Шаблон:Cite journal
  11. ↑ Шаблон:Cite web
  12. ↑ Шаблон:Cite journal
  13. ↑ Шаблон:Cite journal
  14. ↑ Шаблон:Cite web
  15. ↑ Шаблон:Cite journal
  16. ↑ Шаблон:Citation
  17. ↑ 17,00 17,01 17,02 17,03 17,04 17,05 17,06 17,07 17,08 17,09 17,10 Шаблон:Cite journal
  18. ↑ Шаблон:Cite web
  19. ↑ 19,0 19,1 19,2 19,3 19,4 19,5 19,6 19,7 Шаблон:Cite web
  20. ↑ Шаблон:Cite web
  21. ↑ 21,0 21,1 21,2 21,3 21,4 Шаблон:Cite journal
  22. ↑ 22,0 22,1 22,2 Шаблон:Cite web
  23. ↑ 23,0 23,1 Шаблон:Cite web
  24. ↑ 24,0 24,1 Шаблон:Cite web
  25. ↑ Шаблон:Cite web
  26. ↑ Шаблон:Cite web
  27. ↑ Шаблон:Cite web
  28. ↑ 28,0 28,1 Шаблон:Cite web
  29. ↑ Шаблон:Cite web


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