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Upsilon Andromedae

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Upsilon Andromedae
UAnd planets.png
A conception of Upsilon Andromedae A, here showing 2 out of 4 known planets.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Andromeda
Right ascension 01h 36m 47.84216s[1]
Declination +41° 24′ 19.6443″[1]
Apparent magnitude (V) 4.09[2]
Spectral type F8V[2] + M4.5V[3]
Apparent magnitude (B) 4.63[2]
U−B color index 0.06
B−V color index 0.54
V−R color index 0.30[4]
R−I color index 0.30[4]
Radial velocity (Rv) −28.9±0.9[2] km/s
Proper motion (μ) RA: −173.33±0.20[1] mas/yr
Dec.: −381.80±0.13[1] mas/yr
Parallax (π) 73.71 ± 0.10[4] mas
Distance 44.25 ± 0.06 ly
(13.57 ± 0.02 pc)
Absolute magnitude (MV) 3.44±0.02[5]
υ And A
Mass 1.27±0.06[5] M
Radius 1.480±0.087[6] R
Luminosity 3.57[7] L
Surface gravity (log g) 4.0±0.1[5] cgs
Temperature 6213±44[8] K
Metallicity [Fe/H] 0.09±0.06[5] dex
Rotation 7.3±0.04 d[9]
Rotational velocity (v sin i) 9.5±0.8[5] km/s
Age 3.12 ± 0.2[4] Gyr
Other designations
Titawin, 50 Andromedae, BD+40 332, CCDM 01367+4125, FK5 1045, GC 1948, GCTP 331.00, Gl 61, HD 9826, HIP 7513, HR 458, LTT 10561, SAO 37362, WDS 01368+4124A.
Database references
Extrasolar Planets
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

Upsilon Andromedae (υ Andromedae, abbreviated Upsilon And, υ And) is a binary star located approximately 44 light-years from Earth in the constellation of Andromeda. The system consists of an F-type main-sequence star (designated υ Andromedae A, also named Titawin[10]) and a smaller red dwarf (υ Andromedae B).

As of 2010, four extrasolar planets (designated Upsilon Andromedae b, c, d and e; the first three named Saffar, Samh and Majriti, respectively) are believed to orbit υ Andromedae A. All four are likely to be jovian planets that are comparable in size to Jupiter. This was both the first multiple-planet system to be discovered around a main-sequence star, and the first multiple-planet system known in a multiple star system.


υ Andromedae (Latinised to Upsilon Andromedae) is the system's Bayer designation. Under the rules for naming objects in binary star systems, the two components are designated A and B.[11] Under the same rules, the first planet discovered orbiting υ Andromedae A should be designated υ Andromedae Ab. Though this more formal form is occasionally used to avoid confusion with the secondary star υ Andromedae B, it is more commonly referred to as υ Andromedae b. The other planets discovered were designated υ Andromedae c, d, and e, in order of their discovery.

In July 2014 the International Astronomical Union (IAU) launched a process for giving proper names to certain exoplanets and their host stars.[12] The process involved public nomination and voting for the new names.[13] In December 2015, the IAU announced the winning names were Titawin for υ Andromedae A and Saffar, Samh and Majriti for three of its planets (b, c, and d, respectively).[14]

The winning names were those submitted by the Vega Astronomy Club of Morocco. The star is named after the settlement in northern Morocco and UNESCO World Heritage Site now known as the medina (old town) of Tétouan. The planets honour the 10th and 11th Century astronomers Ibn al-Saffar, Ibn al-Samh and Maslama al-Majriti of Muslim Spain.[15]

In 2016, the IAU organized a Working Group on Star Names (WGSN)[16] to catalog and standardize proper names for stars. In its first bulletin of July 2016,[17] the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.[10]

In Chinese, 天大將軍 (Tiān Dà Jiāng Jūn), meaning Heaven's Great General, refers to an asterism consisting of Upsilon Andromedae, Gamma Andromedae, Phi Persei, 51 Andromedae, 49 Andromedae, Chi Andromedae, Tau Andromedae, 56 Andromedae, Beta Trianguli, Gamma Trianguli and Delta Trianguli. Consequently, Upsilon Andromedae itself is known as 天大將軍六 (Tiān Dà Jiāng Jūn liù, English: the Sixth Star of Heaven's Great General.).[18]

Stellar system[edit]

Distance and visibility[edit]

Upsilon Andromedae is located fairly close to the Solar System: the parallax of Upsilon Andromedae A was measured by the Hipparcos astrometry satellite as 74.12 milliarcseconds, corresponding to a distance of 13.49 parsecs (44 light years).[1] Upsilon Andromedae A has an apparent magnitude of +4.09, making it visible to the naked eye even under moderately light-polluted skies, about 10 degrees east of the Andromeda Galaxy. The dimmer star Upsilon Andromedae B is only visible with a telescope.

Upsilon Andromedae A[edit]

Upsilon Andromedae A is a yellow-white dwarf of spectral type F8V, similar to the Sun, but younger, more massive, and more luminous. According to its entry in the Geneva–Copenhagen survey, the star is around 3.1 billion years old and has a similar proportion of iron relative to hydrogen to the Sun.[19] At around 1.3 solar masses, it will have a shorter lifetime than the Sun. The amount of ultraviolet radiation received by any planets in the star's habitable zone would be similar to the ultraviolet flux the Earth receives from the Sun.[20]

Upsilon Andromedae A was ranked 21st in the list of top 100 target stars for NASA's cancelled Terrestrial Planet Finder mission.[21]

Upsilon Andromedae B[edit]

Upsilon Andromedae B is a red dwarf of spectral type M4.5V located at a projected separation of 750 AU from the primary star. The true separation between the two stars is unknown because the displacement along the line of sight between Earth and the Upsilon Andromedae stars is unknown, so this value is a minimum separation. Based upon its motion through space, this is a common proper motion companion to the primary. It was discovered in 2002 in data collected as part of the Two Micron All Sky Survey.[3] The star is less massive and far less luminous than the Sun.

The Washington Double Star Catalog lists two optical components; however, these do not share the system's proper motion and only appear close to Upsilon Andromedae because they happen to lie near the same line of sight.[22]

Planetary system[edit]

The Upsilon Andromedae A planetary system[23]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (Saffar) 0.62±0.09[24] MJ 0.0595±0.0034 4.62±0.23[24] 0.022±0.007[24] 30-90°
c (Samh) 13.98+2.3
[4] MJ
0.832±0.048 241.26±0.64[24] 0.260±0.079[24] 7.9 ± 1[4]°
d (Majriti) 10.25+0.7
[4] MJ
2.53±0.15 1276.46±0.57[24] 0.299±0.072[24] 23.8 ± 1[4]° ~1.02 RJ
e 0.96±0.14[24] MJ 5.2456±0.00067 3848.86±0.74[24] 0.0055±0.0004[24]

The star rotates at an inclination of 58+9
degrees relative to Earth.[9]

The innermost planet of the Upsilon Andromedae system was discovered in 1996 and announced in January 1997, together with the planet of Tau Boötis and the innermost planet of 55 Cancri.[25] The discovery was made by Geoffrey Marcy and R. Paul Butler, both astronomers at San Francisco State University. The planet, designated Upsilon Andromedae b, was discovered by measuring changes in the star's radial velocity induced by the planet's gravity. Because of its closeness to the parent star, it induced a large wobble which was detected relatively easily. The planet appears to be responsible for enhanced activity in the chromosphere of its star.[26]

Artist's conception of the planets of Upsilon Andromedae.

Even when this planet was taken into account, there still remained significant residuals in the radial velocity measurements, and it was suggested there might be a second planet in orbit. In 1999, astronomers at both San Francisco State University and the Harvard-Smithsonian Center for Astrophysics independently concluded that a three-planet model best fit the data.[27] The two outer planets were designated Upsilon Andromedae c and Upsilon Andromedae d in order of increasing distance from the star. Both of these planets are in more eccentric orbits than any of the planets in the Solar System (including Pluto).[28] Upsilon Andromedae d resides in the system's habitable zone.[20]

The system is not coplanar, with each other or with the stellar rotation. The mutual inclination between c and d is 30 degrees.[4] In 2001, preliminary astrometric measurements suggested the orbit of the outermost planet is inclined at 155.5° to the plane of the sky.[29] However, subsequent investigation of the data reduction techniques used suggests that the Hipparcos measurements are not precise enough to adequately characterize the orbits of substellar companions.[30] Astrometry of the innermost planet, meanwhile, constrained its inclination to 30-90 degrees. Full publication is expected in 2008.[31] The orbit of Upsilon Andromedae c gradually oscillates between circular and eccentric states every 6,700 years. The existence of further planets too small or distant to detect has not been ruled out, though the presence of Jupiter-mass planets as close as 5 AU from Upsilon Andromedae A would make the system unstable.[32]

Some simulations show that the eccentricity of the system's planets may have arisen from a close encounter between the outer planet and a fourth planet, with the result that the fourth planet was ejected from the system or destroyed.[33] If so, the rogue planet would have had to eject immediately; it is unclear how likely this situation might be. Other models are possible.[34] However, a fourth planet (Upsilon Andromedae e) was discovered in 2010. This planet is in a 3:1 resonance with Upsilon Andromedae d.[35]

Upsilon Andromedae does not appear to have a circumstellar dust disk similar to the Kuiper belt in the Solar System.[36] This may be the result of perturbations from the companion star removing material from the outer regions of the Upsilon Andromedae A system.[3]

See also[edit]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d "NLTT 5367 -- High proper-motion Star". SIMBAD Astronomical Object Database. Centre de Données astronomiques de Strasbourg. Retrieved 2009-05-20. 
  3. ^ a b c Lowrance, Patrick J.; Kirkpatrick, J. Davy; Beichman, Charles A. (2002). "A Distant Stellar Companion in the υ Andromedae System". The Astrophysical Journal Letters. 572 (1): L79–L81. arXiv:astro-ph/0205277Freely accessible. Bibcode:2002ApJ...572L..79L. doi:10.1086/341554. 
  4. ^ a b c d e f g h i McArthur, Barbara E.; et al. (2010). "New Observational Constraints on the υ Andromedae System with Data from the Hubble Space Telescope and Hobby Eberly Telescope" (PDF). The Astrophysical Journal. 715 (2): 1203. Bibcode:2010ApJ...715.1203M. doi:10.1088/0004-637X/715/2/1203. 
  5. ^ a b c d e Fuhrmann, Klaus; Pfeiffer, Michael J.; Bernkopf, Jan (August 1998), "F- and G-type stars with planetary companions: upsilon Andromedae, rho (1) Cancri, tau Bootis, 16 Cygni and rho Coronae Borealis", Astronomy and Astrophysics, 336: 942–952, Bibcode:1998A&A...336..942F. 
  6. ^ van Belle, Gerard T.; von Braun, Kaspar (2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars". The Astrophysical Journal. 694 (2): 1085–1098. arXiv:0901.1206Freely accessible. Bibcode:2009ApJ...694.1085V. doi:10.1088/0004-637X/694/2/1085. 
  7. ^ Takeda, Yoichi (April 2007), "Fundamental Parameters and Elemental Abundances of 160 F-G-K Stars Based on OAO Spectrum Database", Publications of the Astronomical Society of Japan, 59 (2): 335–356, Bibcode:2007PASJ...59..335T, doi:10.1093/pasj/59.2.335. 
  8. ^ "Exoplanets Data Explorer". Retrieved 4 September 2016. 
  9. ^ a b Simpson, E. K.; et al. (November 2010), "Rotation periods of exoplanet host stars", Monthly Notices of the Royal Astronomical Society, 408 (3): 1666–1679, arXiv:1006.4121Freely accessible, Bibcode:2010MNRAS.408.1666S, doi:10.1111/j.1365-2966.2010.17230.x. , as "HD 9826".
  10. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  11. ^ Hartkopf, William I.; Mason, Brian D. "Addressing confusion in double star nomenclature: The Washington Multiplicity Catalog". U.S. Naval Observatory. Retrieved 2016-01-19. 
  12. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. 9 July 2014
  13. ^ NameExoWorlds The Process
  14. ^ Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
  15. ^ NameExoWorlds The Approved Names
  16. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. 
  17. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016. 
  18. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日
  19. ^ Holmberg; et al. (2007). "Record 970". Geneva-Copenhagen Survey of Solar neighbourhood. Retrieved 19 November 2008. 
  20. ^ a b Buccino, Andrea P.; et al. (2006). "Ultraviolet Radiation Constraints around the Circumstellar Habitable Zones". Icarus. 183 (2): 491–503. arXiv:astro-ph/0512291Freely accessible. doi:10.1016/j.icarus.2006.03.007. 
  21. ^ Mullen, Leslie (2 June 2011). "Rage Against the Dying of the Light". Astrobiology Magazine. Retrieved 2011-06-07. 
  22. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I. "Washington Double Star Catalog". United States Naval Observatory. Retrieved 2012-06-25. 
  23. ^ Wright, J. T.; et al. (2009). "Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems". The Astrophysical Journal. 693 (2): 1084–1099. arXiv:0812.1582Freely accessible. Bibcode:2009ApJ...693.1084W. doi:10.1088/0004-637X/693/2/1084. 
  24. ^ a b c d e f g h i j Ligi, R.; et al. (2012). "A new interferometric study of four exoplanet host stars : θ Cygni, 14 Andromedae, υ Andromedae and 42 Draconis". Astronomy & Astrophysics. 545: A5. arXiv:1208.3895Freely accessible. Bibcode:2012A&A...545A...5L. doi:10.1051/0004-6361/201219467. 
  25. ^ Butler, R. Paul; et al. (1997). "Three New 51 Pegasi-Type Planets". The Astrophysical Journal Letters. 474 (2): L115–L118. Bibcode:1997ApJ...474L.115B. doi:10.1086/310444. 
  26. ^ Shkolnik, E.; et al. (2005). "Hot Jupiters and Hot Spots: The Short- and Long-term Chromospheric Activity on Stars with Giant Planets". The Astrophysical Journal. 622 (2): 1075–1090. arXiv:astro-ph/0411655Freely accessible. Bibcode:2005ApJ...622.1075S. doi:10.1086/428037. 
  27. ^ Butler, R. Paul; et al. (1999). "Evidence for Multiple Companions to υ Andromedae". The Astrophysical Journal. 526 (2): 916–927. Bibcode:1999ApJ...526..916B. doi:10.1086/308035. 
  28. ^ Butler, R. P.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493Freely accessible. Bibcode:2006ApJ...646..505B. doi:10.1086/504701.  (web version)
  29. ^ Han, Inwoo; Black, David C.; Gatewood, George (2001). "Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions". The Astrophysical Journal Letters. 548 (1): L57–L60. Bibcode:2001ApJ...548L..57H. doi:10.1086/318927. 
  30. ^ Pourbaix, D.; Arenou, F. (2001). "Screening the Hipparcos-based astrometric orbits of sub-stellar objects". Astronomy and Astrophysics. 372 (3): 935–944. arXiv:astro-ph/0104412Freely accessible. Bibcode:2001A&A...372..935P. doi:10.1051/0004-6361:20010597. 
  31. ^ Benedict, George F.; McArthur, B. E.; Bean, J. L. (2007). "The υ Andromedae Planetary System - Hubble Space Telescope Astrometry and High-precision Radial Velocities". Bulletin of the American Astronomical Society. 38: 185. Bibcode:2007AAS...210.7802B.  Announced American Astronomical Society Meeting 210, #78.02
  32. ^ Lissauer, J.; Rivera, E. (2001). "Stability analysis of the planetary system orbiting υ Andromedae. II. Simulations using new Lick observatory fits". The Astrophysical Journal. 554 (2): 1141–1150. Bibcode:2001ApJ...554.1141L. doi:10.1086/321426. 
  33. ^ Ford, Eric B.; et al. (2005). "Planet-planet scattering in the upsilon Andromedae system". Nature. 434 (7035): 873–876. arXiv:astro-ph/0502441Freely accessible. Bibcode:2005Natur.434..873F. doi:10.1038/nature03427. PMID 15829958. 
  34. ^ Rory Barnes; Richard Greenberg (2008). "Extrasolar Planet Interactions". arXiv:0801.3226v1Freely accessible [astro-ph]. 
  35. ^ Curiel, S.; et al. (2011). "A fourth planet orbiting υ Andromedae". Astronomy & Astrophysics. 525: A78. Bibcode:2011A&A...525A..78C. doi:10.1051/0004-6361/201015693. 
  36. ^ Trilling, D. E.; Brown, R. H.; Rivkin, A. S. (2000). "Circumstellar dust disks around stars with known planetary companions". The Astrophysical Journal. 529 (1): 499–505. Bibcode:2000ApJ...529..499T. doi:10.1086/308280. 

External links[edit]

Coordinates: Sky map 01h 36m 47.8s, 41° 24′ 20″