HD 21749

HD 21749 (HIP 16069, 2MASS J03265922-6329569) is an orange main-sequence star[4] about 0.68 the mass of the Sun in the constellation Reticulum, located about 53 ly (16 pc) from Earth.[2] On 7 January 2019, it was announced that the star has two exoplanets: a possibly rocky, hot sub-Neptune-sized exoplanet, named HD 21749b; and, a sub-Earth exoplanet, tentatively named HD 21749c (aka, TOI-186.02).[2][6][7] These exoplanets were discovered by the Transiting Exoplanet Survey Satellite (TESS).[2]

HD 21749[1]

HD 21749 – star in the constellation Reticulum
Observation data
Epoch       Equinox
Constellation Reticulum[2]
Right ascension  03h 26m 59.22s[1]
Declination −63° 29′ 56.9″[1]
Apparent magnitude (V) 8.143[3]
Characteristics
Spectral type K4.5V[4]
Astrometry
Radial velocity (Rv)59.46 ± 0.12[5] km/s
Proper motion (μ) RA: 355.084[5] mas/yr
Dec.: −247.460[5] mas/yr
Parallax (π)61.2455 ± 0.0264[5] mas
Distance53.25 ± 0.02 ly
(16.328 ± 0.007 pc)
Details
Mass0.68 M☉
Radius0.76 R☉
Temperature4571 K
Other designations
CD−63 110 A, CPD−63 232 A, GJ 143, HIP 16069, SAO 248808, WDS J03270-6330A, TYC 8870-01392-1 A, 2MASS J03265922-6329569[1], TOI 186
Database references
SIMBADdata
Extrasolar Planets
Encyclopaedia		21749 data

Stellar characteristics

HD 21749 is a star that is approximately 68% the mass of and 76% the radius of the Sun. It has a surface temperature of 4571 K.[1] In comparison, the Sun has a surface temperature of 5778 K.[8]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 8.143.[3]

Planetary system

HD 21749 has two known planets orbiting around it:[2] HD 21749b is a confirmed hot Neptune-sized, possibly rocky, exoplanet; and, HD 21749c is a sub-Earth-sized exoplanet.[2]

The HD 21749 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 23.20 M⊕ — 35.6077 — — 2.836 R⊕
c[6][7] ? M⊕ 0.0695 7.8 — — 0.892 R⊕
HD 21749 star and confirmed HD 21749b exoplanet[2]
gollark: Alternatively, just use `yemmel-simulator` from switchcraft's ROM.
gollark: With a Markov chain thingy and a set of past messages, we should be able to generate hydraz-like messages easily.
gollark: That second one seems much nicer and terser.
gollark: Nuvar.
gollark: PotatOS actually prints strings backwards 1/5 of the time.

See also

References
  1. Staff (2019). "Stellar Overview Page - HD 21749". NASA Exoplanet Archive. Retrieved 8 January 2019.
  2. Overbye, Dennis (7 January 2019). "Another Day, Another Exoplanet: NASA's TESS Keeps Counting More". The New York Times. Retrieved 8 January 2019.
  3. "HD 21749". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 8 January 2018.
  4. Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637.
  5. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  6. Massachusetts Institute of Technology (16 April 2019). "TESS discovers its first Earth-sized planet - Orbiting a nearby star, the new planet is the smallest identified so far by the TESS mission". EurekAlert!. Retrieved 16 April 2019.
  7. Dragomir, Diana; et al. (15 April 2019). "TESS discovers its first Earth-sized planet - Orbiting a nearby star, the new planet is the smallest identified so far by the TESS mission" (PDF). The Astrophysical Journal Letters. 875 (2). doi:10.3847/2041-8213/ab12ed.
  8. Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 8 January 2019.

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