Astronomy:HD 131399

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Short description: Star in the constellation Centaurus
HD 131399
File:SPHERE observations of the planet HD 131399Ab.tif
SPHERE image of HD 131399 A (top left), B and C (bottom right), and the background object (center)
Credit: ESO/K. Wagner et al.
Observation data
Equinox J2000.0]] (ICRS)
Constellation Centaurus
Right ascension  14h 54m 25.30919s[1]
Declination −34° 08′ 34.0412″[1]
Apparent magnitude (V) 7.07[2]
Spectral type A1V + G + K[3]
Radial velocity (Rv)0.30 ± 1.3[4] km/s
[5] pc)
Proper motion (μ) RA: −30.702[6] mas/yr
Dec.: −30.774[6] mas/yr
Parallax (π)9.7480 ± 0.0357[6] mas
Distance335 ± 1 ly
(102.6 ± 0.4 pc)
Absolute magnitude (MV)1.89[7]
Proper motion (μ) RA: −31.523[8] mas/yr
Dec.: −31.047[8] mas/yr
Parallax (π)9.3021 ± 0.0633[8] mas
Distance351 ± 2 ly
(107.5 ± 0.7 pc)
Period (P)3556 ± 36 yr
Semi-major axis (a)3.56 ± 0.03″
(349 ± 28 au)
Eccentricity (e)0.13 ± 0.05
Inclination (i)45 to 65°
Longitude of the node (Ω)265 ± 20[note 1]°
Periastron epoch (T)B 502 ± 33
Argument of periastron (ω)
145.3 ± 15[note 2]°
[5] Myr
HD 131399 A
[7] M
[7] R
[7] L
Surface gravity (log g)4.37±0.10[7] cgs
Temperature9,200±100[7] K
Rotational velocity (v sin i)26±2[7] km/s
HD 131399 B
Mass0.95±0.04[5] M
Surface gravity (log g)4.40±0.03[5] cgs
[5] K
HD 131399 C
Mass0.35±0.04[5] M
Surface gravity (log g)4.45±0.05[5] cgs
Temperature3,460±60[5] K
Other designations
Database references

HD 131399 is a star system in the constellation of Centaurus. Based on the system's electromagnetic spectrum, it is located around 351 light-years (107.9 parsecs) away.[5] The total apparent magnitude is 7.07,[5] but because of interstellar dust between it and the Earth, it appears 0.22 ± 0.09 magnitudes dimmer than it should be.[5]

The brightest star, is a young A-type main-sequence star, and further out are two lower-mass stars.[3] A Jupiter-mass planet or a low-mass brown dwarf was once thought to be orbiting the central star, but this has been ruled out.[5][9]

Stellar system

The brightest star in the HD 131399 system is designated HD 131399 A. Its spectral type is A1V,[3] and it is 2.08 times as massive as the Sun.[5] The two lower-mass stars are designated HD 131399 B and C, respectively. B is a G-type main-sequence star, while HD 131399 C is a K-type main-sequence star.[3] Both stars are less massive than the Sun.[5]

HD 131399 B and C are located very close to each other, and the two orbit each other at about 10 AU.[10] In turn, the B-C pair orbits the central star A at a distance of 349 astronomical units (au). This orbit takes about 3,600 years to complete, and it has an eccentricity of about 0.13[3] The entire system is about 21.9 million years old.[5]

One paper has reported that HD 131399 A has a companion in an inclined 10-day orbit with a semi-major axis of 0.1 astronomical unit|AU.[11] HD 131399 A has been described as a "nascent Am star"; although it has a very slow projected rotation rate and would be expected to show chemical peculiarities, its spectrum is relatively normal, possibly due to its young age.[7]

Planetary system

File:An artist’s impression of planet in the HD 131399 system.tif The claimed discovery of a massive planet, named HD 131399 Ab, was announced in a paper published in the journal Science.[3] The object was imaged using the SPHERE imager of the Very Large Telescope at the European Southern Observatory, located in the Atacama Desert of Chile , and announced in a July 2016 paper in the journal Science.[3][12] It was thought to be a T-type object with a mass of 4 ± 1 MJ,[3] but its orbit would have been unstable, causing it to be ejected between the primary's red giant phase and white dwarf phase.[13] This was the first exoplanet candidate to be discovered by SPHERE. The image was created from two separate SPHERE observations: one to image the three stars and one to detect the faint planet.[14] After its discovery, the team unofficially named the system "Scorpion-1" and the planet "Scorpion-1b", after the survey that prompted its discovery, the Scorpion Planet Survey (principal investigator: Daniel Apai).[15]

In May 2017, observations made by the Gemini Planet Imager and including a reanalysis of the SPHERE data suggest that this target is, in fact, a background star. This object's spectrum seems to be like that of a K-type or M-type dwarf, not a T-type object as first thought. It also initially appeared to be associated with HD 131399, but this was because of its unusually high proper motion (in the top 4% fastest-moving stars).[5] After subsequent data published in 2022 confirmed that the object is a background star, the paper announcing the putative discovery was retracted.[9][16]


The planet was thought to be about 16 million years old, with a mass of 4 (± 1) MJ (Jupiter masses), and a temperature of 850 K (577 °C; 1,070 °F) (± 50 K), which would make it one of the coldest and least massive directly imaged exoplanets.[10] Its atmosphere was shown to contain both water and methane through the use of near-infrared spectroscopy (1.4-1.6 μm).[3] Scientists believed it was unlikely that the planet harbored life due to it being gaseous. The planet was said to have "no liquid water, extremely powerful winds, and no surface; just below the uppermost layer of the atmosphere it rains liquid iron droplets."[17] One orbit of HD 131399 Ab was thought to take 550 years.[3][12]


  1. 1.0 1.1 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode2007A&A...474..653V. 
  2. Høg, E. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. Bibcode2000A&A...355L..27H. 
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 Wagner, K.; Apai, D.; Kasper, M.; Kratter, K.; McClure, M.; Robberto, M.; Beuzit, J.-L. (2016). "Direct imaging discovery of a Jovian exoplanet within a triple-star system". Science 353 (6300): 673–8. doi:10.1126/science.aaf9671. PMID 27386921. Bibcode2016Sci...353..673W.  (Retracted, see doi:10.1126/science.abq1709)
  4. Kharchenko, N. V. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten 328 (9): 889. doi:10.1002/asna.200710776. Bibcode2007AN....328..889K. 
  5. 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 5.15 Nielsen, Eric L. (2017). "Evidence that the Directly-Imaged Planet HD 131399 Ab is a Background Star". The Astronomical Journal 154 (6): 218. doi:10.3847/1538-3881/aa8a69. Bibcode2017AJ....154..218N. 
  6. 6.0 6.1 6.2 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Przybilla, N.; Aschenbrenner, P.; Buder, S. (2017). "Candidate exoplanet host HD 131399A: A nascent Am star". Astronomy & Astrophysics 604: L9. doi:10.1051/0004-6361/201731384. Bibcode2017A&A...604L...9P. 
  8. 8.0 8.1 8.2 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  9. 9.0 9.1 Wagner, Kevin; Apai, Dániel; Kasper, Markus; Kratter, Kaitlin; McClure, Melissa; Robberto, Massimo; Beuzit, Jean-Luc (2022-04-15). "Retraction" (in en). Science 376 (6590): 255. doi:10.1126/science.abq1709. ISSN 0036-8075. PMID 35420970. 
  10. 10.0 10.1 "HD 131399Ab: Astronomers Find Super-Jupiter in Triple-Star System | Astronomy |" (in en-US). 
  11. Lagrange, A.-M.; Keppler, M.; Beust, H.; Rodet, L.; Meunier, N.; Lillo-Box, J.; Bonnefoy, M.; Galland, F. (2017). "Discovery of a stellar companion to HD 131399A". Astronomy & Astrophysics 608: L9. doi:10.1051/0004-6361/201730978. Bibcode2017A&A...608L...9L. 
  12. 12.0 12.1 "This strange new planet has three suns". CBS News. 7 July 2016. 
  13. Veras, Dimitri; Mustill, Alexander J.; Gänsicke, Boris T. (2017). "The unstable fate of the planet orbiting the a star in the HD 131399 triple stellar system". Monthly Notices of the Royal Astronomical Society 465 (2): 1499. doi:10.1093/mnras/stw2821. Bibcode2017MNRAS.465.1499V. 
  14. "A Surprising Planet with Three Suns". ESO. 
  15. Miller, Michael (12 April 2017). "UC mountaineer, galactic explorer". University of Cincinnati. 
  16. Oransky, Ivan (14 April 2022). "Triple sunrise, triple sunset: Science paper retracted when it turns out a planet is a star". 
  17. "16-million-year-old planet with three suns discovered". MSN. 8 July 2016. 


  1. There are two solutions; the other one is 75 ± 10°.
  2. There are two solutions; the other one is 310 ± 10°.