HD 190228

HD 190228 is a star located in the constellation Vulpecula. Its apparent magnitude is 7.31 and the absolute magnitude is 3.34. The distance is 205 light years from Earth. The star is definitely old with age over 10 billion years and it is metal-poor.

HD 190228
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Vulpecula
Right ascension  20h 03m 00.7728s[1]
Declination +28° 18′ 24.6849″[1]
Apparent magnitude (V) 7.307
Characteristics
Spectral type G5IV
Astrometry
Proper motion (μ) RA: 104.146±0.046[1] mas/yr
Dec.: −69.806±0.043[1] mas/yr
Parallax (π)15.9164 ± 0.0305[1] mas
Distance204.9 ± 0.4 ly
(62.8 ± 0.1 pc)
Orbit[2]
Period (P)1146.0 ± 16.0 d
Eccentricity (e)0.50 ± 0.04
Inclination (i)4.3+1.8
−1.0°
Longitude of the node (Ω)61.0+22.7
−22.9°
Argument of periastron (ω)
(primary)		100.7 ± 3,2°
Details
HD 190228
Mass0.83[3] M☉
Surface gravity (log g)4.02 ± 10[3] cgs
Temperature5360 ± 40[3] K
Metallicity [Fe/H]–0.24 ± 0.06[3] dex
HD 190228 b
Mass0.0472 ± 0.0141[2] M☉
Other designations
BD+27° 3593, GCRV 70273, HIP 98714, SAO 88118
Database references
SIMBADdata
ARICNSdata
Extrasolar Planets
Encyclopaedia		data

In 2000, it was announced that a giant planet was orbiting the star with a minimum mass of 5 Jupiter masses, designated HD 190228 b.[4] The planetary nature of the object was questioned because of the low metal content of the star: giant planets are more likely to be found around high-metallicity stars, so it was argued that the object was more likely to be a brown dwarf.[5] Later astrometric measurements confirmed this: HD 190228 b is in fact a brown dwarf of 49.4 Jupiter masses in a nearly face-on orbit. The brown dwarf takes 1146 days to orbit the star, and the orbit is elliptical with an eccentricity of 0.5.[2]

References
  1. 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. Gaia DR2 record for this source at VizieR.
  2. Sahlmann, J.; et al. (2011). "The companion of HD 190228: Planet or brown dwarf?". Astronomy and Astrophysics. 525. A95. arXiv:1009.5991. Bibcode:2011A&A...525A..95S. doi:10.1051/0004-6361/201015427.
  3. Perrier, C.; et al. (2003). "The ELODIE survey for northern extra-solar planets. I. Six new extra-solar planet candidates". Astronomy and Astrophysics. 410 (3): 1039–1049. arXiv:astro-ph/0308281. Bibcode:2003A&A...410.1039P. doi:10.1051/0004-6361:20031340.
  4. "European Southern Observatory: Six Extrasolar Planets Discovered". SpaceRef Interactive Inc. 7 August 2000. Retrieved 15 August 2009.
  5. Chen, Y. Q.; Zhao, G. (2001). "The companion of HD 190228: Planet or brown dwarf?". Astronomy and Astrophysics. 374 (1): L1–L4. Bibcode:2001A&A...374L...1C. doi:10.1051/0004-6361:20010790.


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