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Upsilon Andromedae b / Saffar

Size comparison of Jupiter with Upsilon Andromedae b
Discovery
Discovered by	Marcy et al.
Discovery site	California and Carnegie Planet Search  United States
Discovery date	June 23, 1996
Detection method	Radial velocity
Orbital characteristics
Apastron	0.0601 AU
Periastron	0.0587 AU
Semi-major axis	0.0594±0.0003 AU
Eccentricity	0.012±0.005
Orbital period (sidereal)	4.617111±0.000014 d (0.01264096 a; 110.8107 h)
Inclination	24±4
Time of periastron	2,450,034.05±0.33
Argument of periastron	44.11±25.56
Semi-amplitude	70.51±0.37
Star	Upsilon Andromedae
Physical characteristics
Mean radius	~1.8RJ
Mass	1.70+0.33 −0.24 MJ

Upsilon Andromedae b (υ Andromedae b, abbreviated Upsilon And b, υ And b), formally named Saffar /ˈsæfɑːr/, is an extrasolar planet approximately 44 light-years away from the Sun in the constellation of Andromeda. The planet orbits its host star, the F-type main-sequence star Upsilon Andromedae A, approximately every five days. Discovered in June 1996 by Geoffrey Marcy and R. Paul Butler, it was one of the first hot Jupiters to be discovered. It is also one of the first non-resolved planets to be detected directly. Upsilon Andromedae b is the innermost-known planet in its planetary system.

In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning name was Saffar for this planet. The winning name was submitted by the Vega Astronomy Club of Morocco and honours the 11th-century astronomer Ibn al-Saffar of Muslim Spain.

Discovery

Upsilon Andromedae b was detected by the variations in its star's radial velocity caused by the planet's gravity. The variations were detected by making sensitive measurements of the Doppler shift of Upsilon Andromedae's spectrum. The planet's existence was announced in January 1997, together with 55 Cancri b and the planet orbiting Tau Boötis.

Like 51 Pegasi b, the first extrasolar planet discovered around a normal star, Upsilon Andromedae b orbits very close to its star, closer than Mercury does to the Sun. The planet takes 4.617 days to complete an orbit, with a semimajor axis of 0.0595 AU.

A limitation of the radial velocity method used to detect Upsilon Andromedae b is that only a lower limit on the mass can be found. The true mass may be much greater depending on the inclination of the orbit. A mass of 1.70 M_J and an inclination of 24° were later found using high-resolution spectroscopy.

Physical characteristics

Given the planet's high mass, it is likely that Upsilon Andromedae b is a gas giant with no solid surface.

The Spitzer Space Telescope measured the planet's temperature, and found that the difference between the two sides of Upsilon Andromedae b is about 1,400 degrees Celsius, ranging from minus 20 to 230 degrees to about 1,400 to 1,650 °C. The temperature difference has led to speculation that Upsilon Andromedae b is tidal locked with the same side always facing Upsilon Andromedae A.

David Sudarsky had, on the assumption that the planet is similar to Jupiter in composition and that its environment is close to chemical equilibrium, predicted Upsilon Andromedae b to have reflective clouds of silicates and iron in its upper atmosphere. The cloud deck instead absorbs the star's radiation; between that and the hot, high-pressure gas surrounding the mantle, exists a stratosphere of cooler gas. The outer shell of dark, opaque, hot cloud is assumed to consist of vanadium and titanium oxides, but other compounds like tholins cannot be ruled out yet.

The chemical elements in the atmosphere can be studied by finding their absorption lines in the thermal spectrum of the planet; given typical planet temperatures, the spectrum has its peak at infrared wavelengths. So far, only water vapor has been detected in this planet, while carbon monoxide and methane are still under the detection limit.

The planet is unlikely to have large moons, since tidal forces would either eject them from orbit or destroy them on short timescales compared to the age of the system.

The planet (with 51 Pegasi b) was deemed a candidate for direct imaging by Planetpol. Preliminary results from polarimetric studies indicate that the planet has a predominately blue color, is 1.36 times as large and 0.74 times as massive as Jupiter, meaning that the mean density is 0.36g/cm. It has a geometric albedo of 0.35 in visible light. In 2016–2017 the direct detection of the planetary thermal emission was claimed, but the detection was questioned in 2021. Tidal heating models predict a similar mass for the planet.

Host star

The planet orbits a (F-type) star named Titawin (Upsilon Andromedae A). The star has a mass of 1.27 M_☉ and a radius of around 1.48 R_☉. It has a temperature of 6,074 K and is 3.12 billion years old. In comparison, the Sun is about 4.6 billion years old. The star is slightly metal-rich, with a metallicity () of 0.09, or about 123% of the solar amount. Its luminosity (L_☉) is 3.57 times that of the Sun.

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 4.09. Therefore, Upsilon Andromedae can be seen with the naked eye.

Effect on the parent star

Upsilon Andromedae b appears to be responsible for increased chromospheric activity on its parent star. Observations suggest that there is a "hot spot" on the star around 169 degrees away from the sub-planetary point. This may be the result of interactions between the magnetic fields of the planet and the star. The mechanism may be similar to that responsible for the activity of RS Canum Venaticorum variable stars, or the interaction between Jupiter and its moon Io.

See also

• 55 Cancri b
• Tau Boötis b
• List of exoplanets discovered before 2000

References

1. ^ Pizkorz, D.; et al. (August 2017). "Detection of Water Vapor in the Thermal Spectrum of the Non-transiting Hot Jupiter Upsilon Andromedae b". The Astronomical Journal. 154 (2): 78. arXiv:1707.01534. Bibcode:2017AJ....154...78P. doi:10.3847/1538-3881/aa7dd8. S2CID 19960378.
2. ^ Deitrick, R.; et al. (January 2015). "The Three-dimensional Architecture of the υ Andromedae Planetary System". The Astrophysical Journal. 798 (1): 46. arXiv:1411.1059. Bibcode:2015ApJ...798...46D. doi:10.1088/0004-637X/798/1/46. S2CID 118409453.
3. NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
4. "NameExoWorlds The Process". Archived from the original on 2015-08-15. Retrieved 2015-09-05.
5. Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
6. "NameExoWorlds The Approved Names". Archived from the original on 2018-02-01. Retrieved 2016-01-17.
7. Butler, R. Paul; et al. (1997). "Three New 51 Pegasi-Type Planets". The Astrophysical Journal. 474 (2): L115 – L118. Bibcode:1997ApJ...474L.115B. doi:10.1086/310444.
8. Butler, R. P.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. S2CID 119067572. (web version)
9. Harrington, J; Hansen BM; Luszcz SH; Seager S; Deming D; Menou K; Cho JY; Richardson LJ (October 27, 2006). "The phase-dependent infrared brightness of the extrasolar planet upsilon Andromedae b". Science. 314 (5799): 623–6. arXiv:astro-ph/0610491. Bibcode:2006Sci...314..623H. doi:10.1126/science.1133904. PMID 17038587. S2CID 20549014.
10. Sudarsky, David; et al. (2003). "Theoretical Spectra and Atmospheres of Extrasolar Giant Planets". The Astrophysical Journal. 588 (2): 1121–1148. arXiv:astro-ph/0210216. Bibcode:2003ApJ...588.1121S. doi:10.1086/374331. S2CID 16004653.
11. Ivan Hubeny; Adam Burrows (2008). "Spectrum and atmosphere models of irradiated transiting extrasolar giant planets". Proceedings of the International Astronomical Union. 4: 239. arXiv:0807.3588. Bibcode:2009IAUS..253..239H. doi:10.1017/S1743921308026458. S2CID 13978248.
12. Barnes, J.; O'Brien, D. (2002). "Stability of Satellites around Close-in Extrasolar Giant Planets". The Astrophysical Journal. 575 (2): 1087–1093. arXiv:astro-ph/0205035. Bibcode:2002ApJ...575.1087B. doi:10.1086/341477. S2CID 14508244.
13. Lucas, P. W.; Hough, J. H.; Bailey, J. A.; Tamura, M.; Hirst, E.; Harrison, D. (11 February 2009). "Planetpol polarimetry of the exoplanet systems 55 Cnc and τ Boo". Monthly Notices of the Royal Astronomical Society. 393 (1): 229–244. arXiv:0807.2568. Bibcode:2009MNRAS.393..229L. doi:10.1111/j.1365-2966.2008.14182.x. S2CID 8684361.
14. S.V. Berdyugina; A.V. Berdyugin; V. Piirola (14 September 2011). "Upsilon Andromedae b in polarized light: New constraints on the planet size, density and albedo". arXiv:1109.3116 .
15. Buzard, Cam; Piskorz, Danielle; Lockwood, Alexandra C.; Blake, Geoffrey; Barman, Travis S.; Benneke, Björn; Bender, Chad F.; Carr, John S. (2021), "Reinvestigation of the Multiepoch Direct Detections of HD 88133 b and Upsilon Andromedae B", The Astronomical Journal, 162 (6): 269, arXiv:2109.13275, Bibcode:2021AJ....162..269B, doi:10.3847/1538-3881/ac2a2c, S2CID 238198093
16. 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/0411655. Bibcode:2005ApJ...622.1075S. doi:10.1086/428037. S2CID 3043910.

External links

• "A Triple-Planet System Orbiting Ups Andromedae". San Francisco State University. Lick Observatory. Retrieved 2008-06-23.
• "Mystery Solved: How The Orbits Of Extrasolar Planets Became So Eccentric". SpaceDaily. 2005-04-14. Retrieved 2008-06-23.
• "NASA's Spitzer Sees Day and Night on Exotic World". NASA. Spitzer Space Telescope. 2006-10-12. Archived from the original on October 22, 2007. Retrieved 2008-06-23.
• "Upsilon Andromedae". The Internet Encyclopedia of Science. Retrieved 2008-06-23.
• "Upsilon Andromedae". The Planet Project. Archived from the original on 2008-05-18. Retrieved 2008-06-23.
• "Upsilon Andromedae 2". SolStation. Retrieved 2008-06-23.
• "The Upsilon Andromedae Planetary System". Harvard-Smithsonian Center for Astrophysics. Retrieved 2008-06-23.

v t e The Upsilon Andromedae system
Upsilon Andromedae A Upsilon Andromedae B
Upsilon Andromedae b Upsilon Andromedae c Upsilon Andromedae d Upsilon Andromedae e?
See also binary stars extrasolar planets

v t e Constellation of Andromeda
Adhil Andromeda in Chinese astronomy List of Andromeda's satellite galaxies List of stars in Andromeda
Stars	Bayer α (Alpheratz) β (Mirach) γ (Almach) δ ε ζ η θ ι κ λ μ ν ξ (Adhil) ο π ρ σ τ υ (Titawin) φ χ ψ ω A b c υ Per (Nembus) Flamsteed 2 3 4 5 6 7 8 9 10 11 12 13 14 (Veritate) 15 18 22 23 26 28 32 36 39 41 44 45 47 55 56 58 59 63 64 65 66 6 Per Variable R T U W Z RT RV RX SU SW TU TW WZ XZ AB AC AD AE AF AR BM BX CC CG CN DS DX EG ET EU FF GO GP GQ GX GR GY HH HN IW KK KX KZ LL LN LP LQ OP OS OU PX PY QR QV QX V385 V428 V439 V455 V529 V807 HR 1 40 56 78 104 122 134 178 275 282 283 289 379 410 483 687 746 748 8884 8925 8950 8962 8973 9011 9074 9075 9105 HD 16175 (Buna) 222155 Other 3XMM J004232.1+411314 ADS 48 HAT-P-6 (Sterrennacht) HAT-P-16 HAT-P-19 HAT-P-28 M31-RV KELT-1 NGC 44 NGC 82 NGC 84 NGC 91 NGC 162 NGC 464 Qatar-3 Qatar-4 Qatar-5 PA-99-N2 WASP-1 WISE 0146+4234 WISE J0005+3737 WISE J004945.61+215120.0
Exoplanets 14 Andromedae b κ Andromedae b υ Andromedae b c d Gliese 15 Ab c HD 13931 b HD 16175 b HAT-P-6b HAT-P-32b WASP-1b WASP-33b Qatar-4b Qatar-5b
Star clusters	NGC 206 272 752 956 7686 Other Mayall II RBC EXT8
Nebulae	NGC 7662
Galaxies	Messier 32 110 NGC 5 11 13 19 20 21 27 39 43 48 49 51 67 68 69 70 71 72 74 76 79 80 81 83 85 86 90 93 94 96 97 108 109 112 140 149 160 169 181 183 184 214 218 226 228 229 233 243 252 258 260 262 280 304 317 389 393 404 425 431 477 512 513 523 528 529 531 536 542 561 605 620 668 679 687 700 703 704 705 708 709 710 712 714 717 721 732 753 759 801 812 834 891 906 910 911 912 913 920 937 980 995 996 999 1000 7640 7836 Numbered I II III IV V VIII IX X XI XVIII XIX XXI Other 3C 66A 3C 66B Andromeda Galaxy Arp 273 Donatiello I UGC 1840
Galaxy clusters Abell 262 NGC 68 group
Astronomical events GRB 101225A SN 1885A (S)
Category

• Upsilon Andromedae
• Exoplanets discovered in 1996
• Giant planets
• Hot Jupiters
• Exoplanets detected by radial velocity
• Exoplanets with proper names