HD 20781 d - Misplaced Pages

Extrasolar planet orbiting HD 20781 in the constellation Fornax

HD 20781 d
Discovery
An artist's impression of HD 20781 d orbiting its host star.
Discovered by	Mayor et al.
Discovery site	La Silla Observatory
Discovery date	2011
Detection method	Doppler spectroscopy (HARPS)
Orbital characteristics
Periastron	0.15 AU
Apoastron	0.18 AU
Semi-major axis	0.1647+0.0076 −0.0083 AU
Eccentricity	0.11+0.05 −0.06
Orbital period (sidereal)	29.1580+0.0102 −0.0100 d
Time of periastron	2,455,511.3258+2.4394 −2.4382 JD
Argument of periastron	60.99°+30.79° −30.03°
Semi-amplitude	2.82+0.17 −0.16 m/s
Physical characteristics
Mean radius	~3.18 R_🜨 (estimate)
Mass	≥10.61+1.20 −1.19 M_🜨

HD 20781 d is an extrasolar planet orbiting the K-type main-sequence star HD 20781 117 light years away in the southern constellation Fornax. It was discovered in 2011 during a survey for southern exoplanets conducted with HARPS using doppler spectroscopy, the radial velocity variations caused by the gravitational pull of the planet. Its existence was confirmed in another survey during 2017.

Naming

This planet was initially reported in a 2011 preprint, which referred to it as HD 20781 b. However, the 2017 paper (published in a journal in 2019) that confirmed the planet designated it HD 20781 d, using the b designation for a different, shorter-period planet.

Properties

Orbit

HD 20781 d takes only 29 days to orbit its host star, classifying it as a hot Neptune. However, its orbit is slightly eccentric, carrying it as close as 0.15 AU and as far as 0.18 AU. HD 20781 d is the second outermost planet in its system after HD 20781 e.

Characteristics

With a minimum mass 10.6 times that of Earth, it is probably a sub-Neptune, a planet that is larger than Earth but smaller than Neptune. Due to indirect detection, most of its properties can't be studied such as inclination, density, and temperature. Due to HD 20781 d's mass, it is estimated to be about 3 times larger than Earth.

References

^ Mayor, M.; Marmier, M.; Lovis, C.; Udry, S.; Ségransan, D.; Pepe, F.; Benz, W.; Bertaux, J.-L.; Bouchy, F.; Dumusque, X.; Curto, G. Lo; Mordasini, C.; Queloz, D.; Santos, N. C. (2011). "The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets". arXiv:1109.2497 .
^ Brennan, Pat. "Exoplanet-catalog". Exoplanet Exploration: Planets Beyond our Solar System. Retrieved 6 February 2022.
^ Udry, S.; Dumusque, X.; Lovis, C.; Ségransan, D.; Diaz, R. F.; Benz, W.; Bouchy, F.; Coffinet, A.; Lo Curto, G.; Mayor, M.; Mordasini, C.; Motalebi, F.; Pepe, F.; Queloz, D.; Santos, N. C.; Wyttenbach, A.; Alonso, R.; Collier Cameron, A.; Deleuil, M.; Figueira, P.; Gillon, M.; Moutou, C.; Pollacco, D.; Pompei, E. (February 2019). "The HARPS search for southern extra-solar planets: XLIV. Eight HARPS multi-planet systems hosting 20 super-Earth and Neptune-mass companions". Astronomy & Astrophysics. 622: A37. arXiv:1705.05153. Bibcode:2019A&A...622A..37U. doi:10.1051/0004-6361/201731173. ISSN 0004-6361.

v t e The HD 20781/HD 20782 system
HD 20781 b c d e
HD 20782 b
See also: binary stars extrasolar planets

Constellation of Fornax

Stars

Bayer	α (Dalim) β γ γ δ ε ζ η η η ι ι κ λ λ μ ν π ρ σ τ υ φ χ χ χ ψ ω
Variable	R TZ UZ
HR	683 858
HD	15337 20781 20782 20868 (Intan)
Other	2MASS J02431371−2453298 HIP 13044 LP 944-20 UDF 2457 WASP-72 (Diya)

Exoplanets	HD 16417 b HD 20781 b c d e HD 20782 b HD 20868 b (Baiduri) TOI-849 b

Star clusters	NGC 1049

Nebulae	NGC 1360

Galaxies

NGC	823 824 922 986 1097 1210 1255 1288 1310 1316 1317 1318 1326 1350 1365 1374 1375 1379 1380 1381 1387 1398 1399 1406 1425 1427
Other	Fornax Dwarf HUDF-JD2 GS-NDG-9422 IC 335 IC 1993 JADES-GS-z14-0 JADES-GS-z7-01-QU MRC 0316-257 PGC 13809 UDF 423 UDFj-39546284 UDFy-38135539

Galaxy clusters	Fornax Cluster

Astronomical events	SN 1992bd SN 1999eu SN 2003B