Editing Upsilon Andromedae

{{Short description|Star in the constellation Andromeda}}
{{About|υ Andromedae|the variable star|U Andromedae}}
{{Starbox begin
| name = υ Andromedae / Titawin
}}
{{Starbox image
 | image=
{{Location mark
|image=Andromeda constellation map.svg|alt=|float=center|width=260
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=υ Andromedae
|x=306|y=396
}}
|caption=Location of υ Andromedae (circled)
}}
{{Starbox observe 2s
| epoch      = J2000.0
| constell   = [[Andromeda (constellation)|Andromeda]]
| component1 = υ And A
| ra1        = {{RA|01|36|47.84154}}<ref name="Gaia EDR3 for A"/>
| dec1       = {{DEC|+41|24|19.6514}}<ref name="Gaia EDR3 for A"/>
| appmag_v1  = 4.10<ref name=Belle/>
| component2 = υ And D{{efn|name=note}}
| ra2        = {{RA|01|36|50.40476}}<ref name="Gaia EDR3 for D"/>
| dec2       = {{DEC|+41|23|32.1228}}<ref name="Gaia EDR3 for D"/>
| appmag_v2  = 
}}
{{Starbox character
| class = F8V<ref name=mk/>&nbsp;+&nbsp;M4.5V<ref name="lowrance"/>
| appmag_1_passband = B
| appmag_1 = 4.63<ref name="SIMBAD"/>
| r-i = 0.30<ref name="McArthur2010">{{cite journal | url=http://hubblesite.org/pubinfo/pdf/2010/17/pdf.pdf |display-authors=1 | last1=McArthur |first1=Barbara E.| last2=Benedict |first2=G. Fritz| last3=Barnes |first3=Rory| last4=Martioli |first4=Eder| last5=Korzennik |first5=Sylvain| last6=Nelan |first6=Ed| last7=Butler |first7=R. Paul | title=New Observational Constraints on the ''υ'' Andromedae System with Data from the ''Hubble Space Telescope'' and ''Hobby Eberly Telescope'' |journal=The Astrophysical Journal |volume=715 |issue=2 |pages=1203 | date=2010 | doi=10.1088/0004-637X/715/2/1203 |bibcode=2010ApJ...715.1203M |s2cid=120127162 }}</ref>
| v-r = 0.30<ref name="McArthur2010"/>
| b-v = 0.54
| u-b = 0.06
}}
{{Starbox astrometry
| component1 = υ And A
| radial_v = {{val|−28.59|0.08}}<ref name=rv/>
| prop_mo_ra = {{val|−171.892}}<ref name="Gaia EDR3 for A"/>
| prop_mo_dec = {{val|−381.815}}<ref name="Gaia EDR3 for A"/>
| parallax = 74.1940
| p_error = 0.2083
| parallax_footnote = <ref name="Gaia EDR3 for A"/>
| absmag_v = {{val|3.44|0.02}}<ref name=aaa336_942/>
| component2 = υ And D{{efn|name=note}}
| radial_v2 =
| prop_mo_ra2 = {{val|−172.437}}<ref name="Gaia EDR3 for D"/>
| prop_mo_dec2 = {{val|−383.824}}<ref name="Gaia EDR3 for D"/>
| parallax2 = 74.1815
| p_error2 = 0.0356
| parallax_footnote2 = <ref name="Gaia EDR3 for D"/>
| absmag_v2 =
}}
{{Starbox detail
| component1 = υ And A
| mass = {{val|1.23|0.03|0.09}}<ref name=Baines2025/>
| radius = {{val|1.57|0.03}}<ref name=Baines2021/>
| gravity = {{val|4.0|0.1}}<ref name=aaa336_942/>
| luminosity = {{val|3.1|0.1}}<ref name=Baines2021/>
| temperature = {{val|6614|77|fmt=commas}}<ref name=Baines2021/>
| habitable_inner = {{val|1.43|0.05}}<ref name=Baines2025/> [[Astronomical unit|AU]]
| habitable_outer = {{Val|2.84|0.08}}<ref name=Baines2025/> AU
| metal_fe = 0.08<ref name=Baines2021/>
| rotation = {{val|7.3|0.04|u=days}}<ref name=mnras408_3_1666/>
| rotational_velocity = {{val|9.5|0.8}}<ref name=aaa336_942/>
| age_gyr = {{val|4.02|1.91|0.82}}<ref name=Baines2025/>
| component2 = υ And D{{efn|name=note}}
| mass2 = 0.2<ref name="lowrance"/>
}}
{{Starbox catalog
| names = Titawin,<ref name="IAU-CSN">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt | title=IAU Catalog of Star Names |access-date=28 July 2016}}</ref> 50&nbsp;Andromedae, [[Bonner Durchmusterung|BD]]+40&nbsp;332, CCDM&nbsp;01367+4125, [[FK5]]&nbsp;1045, GC&nbsp;1948, [[General Catalogue of Trigonometric Parallaxes|GCTP]]&nbsp;331.00, [[Gliese Catalogue of Nearby Stars|Gl]]&nbsp;61, [[Henry Draper catalogue|HD]]&nbsp;9826, [[Hipparcos catalogue|HIP]]&nbsp;7513, [[Harvard Revised catalogue|HR]]&nbsp;458, [[Luyten Two-Tenths catalogue|LTT]]&nbsp;10561, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]]&nbsp;37362, [[PPM Star Catalogue|PPM]]&nbsp;44216, [[Washington Double Star Catalog|WDS]]&nbsp;01368+4124A, 2MASS J01364784+4124200, Gaia DR2 348020448377061376
}}
{{Starbox reference
| Simbad = HD+9826
| Simbad2 = UCAC4+657-006214|sn2=υ And D
| NSTED = ups%20And
| ARICNS =
}}
{{Starbox end}}
'''Upsilon Andromedae''' ('''υ Andromedae''', abbreviated '''Upsilon And''', '''υ And''') is a [[binary star]] located 44 [[light-year]]s from Earth in the [[constellation]] of [[Andromeda (constellation)|Andromeda]]. The system consists of an [[F-type main-sequence star]] (designated υ Andromedae A, officially named '''Titawin''' in the [[Amazigh]] language {{IPAc-en|t|I|t|@|'|w|iː|n}}<!--the Berber allophone of /i/ before the pharyngealized C2 just happens to match the trisyllabic laxing expected for Latinized words-->) and a smaller [[red dwarf]].

{{As of|2015}}, three [[Exoplanet|extrasolar planet]]s (designated [[Upsilon Andromedae b]], [[Upsilon Andromedae c|c]], [[Upsilon Andromedae d|d]]; named Saffar, Samh and Majriti, respectively) are believed to orbit υ Andromedae A. All three are likely to be [[jovian planet]]s that are comparable in size to [[Jupiter]]. This was both the first multiple-[[planetary system|planet system]] to be discovered around a [[main-sequence star]], and the first multiple-planet system known in a multiple-[[star system]].

== Nomenclature ==
''υ Andromedae'' ([[Latinisation of names|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.<ref>{{cite web |last1=Hartkopf |first1=William I. |last2=Mason |first2=Brian D. |title=Addressing confusion in double star nomenclature: The Washington Multiplicity Catalog |url=http://ad.usno.navy.mil/wds/wmc/wmc_post191.html |work=U.S. Naval Observatory |access-date=2016-01-19 |archive-date=2011-05-17 |archive-url=https://web.archive.org/web/20110517130354/http://ad.usno.navy.mil/wds/wmc/wmc_post191.html |url-status=dead }}</ref> 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 a 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 [[NameExoWorlds]], a process for giving proper names to certain exoplanets and their host stars.<ref>[http://www.iau.org/news/pressreleases/detail/iau1404/ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars]. IAU.org. 9 July 2014</ref> The process involved public nomination and voting for the new names.<ref>{{Cite web |url=http://nameexoworlds.iau.org/process |title=NameExoWorlds The Process |access-date=2015-09-05 |archive-date=2015-08-15 |archive-url=https://web.archive.org/web/20150815025117/http://nameexoworlds.iau.org/process |url-status=dead }}</ref> 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).<ref>[http://www.iau.org/news/pressreleases/detail/iau1514/ Final Results of NameExoWorlds Public Vote Released], International Astronomical Union, 15 December 2015.</ref>

The winning names were those submitted by the Vega Astronomy Club of [[Morocco]]. The star is named after the Berber name ''Tiṭṭawin'', ⵜⵉⵟⵟⴰⵡⵉⵏ, of Morocco's [[Tétouan]] city and Tunisia's [[Tataouine]] city, both cities' old town quarters are considered [[UNESCO]] [[World Heritage Site]]s. The planets honour the 10th- and 11th-century astronomers [[Ibn al-Saffar]], [[Ibn al-Samh]] and [[Maslama al-Majriti]] of [[Muslim Spain]].<ref>{{Cite web |url=http://nameexoworlds.iau.org/names |title=NameExoWorlds The Approved Names |access-date=2016-01-17 |archive-date=2018-02-01 |archive-url=https://web.archive.org/web/20180201043609/http://nameexoworlds.iau.org/names |url-status=dead }}</ref>

In 2016, the IAU organized a [[Working Group on Star Names]] (WGSN)<ref name="WGSN">{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}}</ref> to catalog and standardize proper names for stars. In its first bulletin of July 2016,<ref name="WGSN1">{{cite web | url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf | title=Bulletin of the IAU Working Group on Star Names, No. 1 |access-date=28 July 2016}}</ref> 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.<ref name="IAU-CSN"/>

In [[Chinese astronomy|Chinese]], {{lang|zh|天大將軍}} ({{lang|zh-Latn|Tiān Dà Jiāng Jūn}}), meaning ''[[Bond (Chinese constellation)|Heaven's Great General]]'', refers to an [[Asterism (astronomy)|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, the [[Chinese star names|Chinese name]] for Upsilon Andromedae itself is {{lang|zh|天大將軍六}} ({{lang|zh-Latn|Tiān Dà Jiāng Jūn liù}}, {{langx|en|the Sixth Star of Heaven's Great General}}).<ref>{{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0607/ap060710.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日] {{Webarchive|url=https://web.archive.org/web/20110716123113/http://aeea.nmns.edu.tw/2006/0607/ap060710.html |date=2011-07-16 }}</ref>

==Stellar system==
Upsilon Andromedae is located fairly close to the [[Solar System]]: the [[parallax]] of Upsilon Andromedae A was measured by the ''[[Gaia (spacecraft)|Gaia]]'' [[astrometry]] [[satellite]] as 74.19 [[milliarcseconds]], corresponding to a distance of {{convert|44|ly|pc|abbr=off|lk=on|order=flip|2}}.<ref name="Gaia EDR3 for A"/> 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 [[degree (angle)|degrees]] east of the [[Andromeda Galaxy]].

The [[Catalog of Components of Double and Multiple Stars]] and [[Washington Double Star Catalog]] (WDS) both list two companion stars: magnitude 12.6 UCAC3 263-13722 110" away, listed as component B; and magnitude 10.3 F2 star TYC 2822-2067-1 280" away, listed as component C.<ref name="wds">{{cite web |last1=Mason |first1=Brian D. |last2=Wycoff |first2=Gary L. |last3=Hartkopf |first3=William I. |title=Washington Double Star Catalog |url=http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/WDS |url-status=dead |access-date=2012-06-25 |publisher=U.S. Naval Observatory |archive-date=2016-03-14 |archive-url=https://web.archive.org/web/20160314022133/http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/WDS }}</ref>

A fainter and closer star, discovered in 2002, is confusingly referred to in the discovery paper as υ Andromedae B even though that designation is also used for a different companion. This 13th-magnitude [[red dwarf]] is 55" from υ Andromedae A and is believed to be the only one of the companions physically associated, at the same distance and a projected separation of {{val|750|ul=AU}}. It has been added to the WDS as component D.<ref name=wds/>

=== Upsilon Andromedae A ===
Upsilon Andromedae A is a yellow-white dwarf of [[spectral type]] F8V,<ref name=mk/> similar to the Sun, but younger, more massive, and more [[luminosity|luminous]]. It is around [[1 E17 s|four]] [[billion years]] old and has a similar proportion of [[iron]] relative to [[hydrogen]] to the Sun.<ref name=Baines2025/> At around 1.3 [[solar mass]]es,<ref name=Baines2025/> 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.<ref name="buccino">{{cite journal | last1=Buccino | first1=Andrea P. | last2=Lemarchand | first2=Guillermo A. | last3=Mauas | first3=Pablo J. D. |display-authors=1|title=Ultraviolet Radiation Constraints around the Circumstellar Habitable Zones|journal=[[Icarus (journal)|Icarus]] | volume=183 | issue=2 | pages=491–503 | date=2006 | doi=10.1016/j.icarus.2006.03.007 | bibcode=2006Icar..183..491B | arxiv=astro-ph/0512291 | citeseerx=10.1.1.337.8642 | s2cid=2241081 }}</ref>

The X-ray emission of Upsilon Andromedae A is low for a star of its spectral class. This means that the star may be moving, or move soon, out of the [[main sequence]] and expand its radius to become a [[red giant]] star. This is consistent with the upper limits on the age of this star. The absolute magnitude for this star is about 0.6 magnitudes brighter that if it were still on the main sequence.<ref name="poppenhaeger"/>

Upsilon Andromedae A was ranked 21st in the list of top 100 target stars for [[NASA]]'s cancelled [[Terrestrial Planet Finder]] mission.<ref name=Mullen>{{cite web |last1=Mullen |first1=Leslie |title=Rage Against the Dying of the Light |url=http://www.astrobio.net/exclusive/4005/rage-against-the-dying-of-the-light |date=2 June 2011 |work=Astrobiology Magazine |access-date=2011-06-07 |url-status=usurped |archive-url=https://web.archive.org/web/20110604121537/http://www.astrobio.net/exclusive/4005/rage-against-the-dying-of-the-light |archive-date=2011-06-04}}</ref>

The star rotates at an inclination of {{val|58|+9|-7}} degrees relative to Earth.<ref name=mnras408_3_1666/>

=== Upsilon Andromedae B ===
The red dwarf companion has a spectral type M4.5V and is 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 propagation|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 [[2MASS]].<ref name="lowrance">{{cite journal | last1=Lowrance | first1=Patrick J. | last2=Kirkpatrick | first2=J. Davy | last3=Beichman | first3=Charles A. | title=A Distant Stellar Companion in the υ Andromedae System | journal=The Astrophysical Journal Letters | volume=572 | issue=1 | pages=L79–L81 | date=2002 | doi=10.1086/341554 | bibcode=2002ApJ...572L..79L | arxiv=astro-ph/0205277 | s2cid=7111977 }}</ref> The star is less massive and far less luminous than the Sun, and its age seems to be consistent with that of the system.<ref name="poppenhaeger"/>

== Planetary system ==
[[Image:Upsilon Andromedae A System (NASA, ESA).jpg|thumb]]
{{OrbitboxPlanet begin
| name = Upsilon Andromedae A
| table_ref = <ref name=Ligi2012/>
}}
{{OrbitboxPlanet
| exoplanet = [[Upsilon Andromedae b|b (Saffar)]]
| mass = {{val|1.70|0.33|0.24}}<ref name=Pizkorz2017/>
| period = {{val|4.62|0.23}}
| semimajor = {{val|0.0594|0.0003}}<ref name="McArthur2010"/>
| eccentricity = {{val|0.022|0.007}}
| inclination = {{val|24|4}}<ref name=Pizkorz2017/>
| radius = 1.8<ref>{{Cite journal |last1=Deitrick |first1=Russell |last2=Barnes |first2=Rory |last3=McArthur |first3=Barbara |last4=Quinn |first4=Thomas R. |last5=Luger |first5=Rodrigo |last6=Antonsen |first6=Adrienne |last7=Benedict |first7=G. Fritz |date=2014-12-18 |title=The 3-dimensional architecture of the Upsilon Andromedae planetary system |journal=The Astrophysical Journal |volume=798 |issue=1 |pages=46 |doi=10.1088/0004-637X/798/1/46 |issn=1538-4357|arxiv=1411.1059 |bibcode=2015ApJ...798...46D }}</ref>
}}
{{OrbitboxPlanet
| exoplanet = [[Upsilon Andromedae c|c (Samh)]]
| mass = {{val|13.98|2.3|5.3}}<ref name="McArthur2010"/>
| period = {{val|241.26|0.64}}
| semimajor = {{val|0.829|0.043}}<ref name="McArthur2010"/>
| eccentricity = {{val|0.260|0.079}}
| inclination = 7.9 ± 1<ref name="McArthur2010"/>
}}
{{OrbitboxPlanet
| exoplanet = [[Upsilon Andromedae d|d (Majriti)]]
| mass = {{val|10.25|0.7|3.3}}<ref name="McArthur2010"/>
| period = {{val|1276.46|0.57|fmt=commas}}
| semimajor = {{val|2.530|0.014}}<ref name="McArthur2010"/>
| eccentricity = {{val|0.299|0.072}}
| inclination = 23.8 ± 1<ref name="McArthur2010"/>
| radius = 1.02{{citation needed|date=May 2024}}
}}
{{Orbitbox end}}

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]].<ref name="Butler1997"/> The discovery was made by [[Geoffrey Marcy]] and [[R. Paul Butler]], both [[astronomer]]s 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.<ref>{{cite journal | title=Hot Jupiters and Hot Spots: The Short- and Long-term Chromospheric Activity on Stars with Giant Planets | display-authors=1 | last1=Shkolnik | first1=E. | last2=Walker | first2=G. A. H. | last3=Bohlender | first3=D. A. | last4=Gu | first4=P.-G. | last5=Kürster | first5=M. | journal=The Astrophysical Journal | volume=622 | issue=2 | date=2005 | pages=1075–1090 | doi=10.1086/428037 | bibcode=2005ApJ...622.1075S|arxiv = astro-ph/0411655 | s2cid=119356064 }}</ref>

[[File:Upsand.jpg|thumb|right|Artist's conception of the planets of Upsilon Andromedae]]
Even when the first 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.<ref>{{cite journal | display-authors=1 | last1=Butler | first1=R. Paul | last2=Marcy | first2=Geoffrey W. | last3=Fischer | first3=Debra A. | last4=Brown | first4=Timothy M. | last5=Contos | first5=Adam R. | last6=Korzennik | first6=Sylvain G. | last7=Nisenson | first7=Peter | last8=Noyes | first8=Robert W. | title=Evidence for Multiple Companions to υ Andromedae | journal=The Astrophysical Journal | volume=526 | issue=2 | pages=916–927 | date=1999 | doi=10.1086/308035 | bibcode=1999ApJ...526..916B | doi-access=free }}</ref> 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 [[Orbital eccentricity|eccentric]] orbits than any of the planets in the Solar System (including [[Pluto]]).<ref name="Butler(2006)">{{cite journal | display-authors=1 |last1=Butler |first1=R. P. |last2=Wright |first2=J. T. |last3=Marcy |first3=G. W. |last4=Fischer |first4=D. A. |last5=Vogt |first5=S. S. |last6=Tinney |first6=C. G. |last7=Jones |first7=H. R. A. |last8=Carter |first8=B. D. |last9=Johnson |first9=J. A. |last10=McCarthy |first10=C. |last11=Penny |first11=A. J. | doi=10.1086/504701 | title=Catalog of Nearby Exoplanets | journal=The Astrophysical Journal | volume=646 | issue=1 | pages=505–522 | date=2006 | bibcode=2006ApJ...646..505B|arxiv = astro-ph/0607493 |s2cid=119067572 }} ([http://exoplanets.org/planets.shtml web version])</ref> Upsilon Andromedae d resides in the system's [[habitable zone]].<ref name="buccino"/>

The orbital parameters of this three-planet system have been fully determined. The system is not [[coplanar]], with each other or with the stellar rotation, as in our [[Solar System]].<ref name=McArthur2010/> Samh, planet c, has an orbit significantly inclined from those of the other two, and from the perspective of Earth is inclined by only about 8 degrees from the celestial sphere; when it was first discovered, it was thought to have a mass closer to only 2 Jupiter masses due to a comparatively small radial velocity signal. Simulations shows that the measured configuration of the planets produces indeed stable orbits for at least 100 million years, where planets ''b'' and ''d'' remain roughly coplanar. [[General relativity]] is expected to have strong effects on planet ''b'', because it orbits at a distance of just ~0.05 AU from the parent star. The [[apsis|apsides]] of planet ''c'' and ''d'', instead, oscillates with time;<ref name=Pizkorz2017/> the orbit of Upsilon Andromedae c thus returns to a nearly circular state every 9,000 years. The eccentricity of those planets may have arisen from a close encounter between the outer planet and a fourth planet, with the result that the third planet was ejected from the system or destroyed.<ref>{{cite journal | display-authors=1 | first1=Eric B. | last1=Ford | first2=Verene | last2=Lystad | first3=Frederic A. | last3=Rasio | title=Planet-planet scattering in the upsilon Andromedae system | journal=[[Nature (journal)|Nature]] | volume=434 | pages=873–876 | date=2005 | doi=10.1038/nature03427 | pmid=15829958 | issue=7035 | bibcode=2005Natur.434..873F | arxiv=astro-ph/0502441 | s2cid=4324250 }}</ref> Such a mechanism could have been triggered by perturbations on the orbit of the companion star, which arise from close encounters with other stars and from the tidal field of the [[Milky Way]].<ref>{{cite journal|last1=Kaib |first1=N.A. |last2=Raymond |first2=S.N.| last3=Duncan|first3=M.|title=Planetary system disruption by Galactic perturbations to wide binary stars|journal=[[Nature (journal)|Nature]]|volume=493|issue=7432|pages=381–384|date=January 2013|doi=10.1038/nature11780|pmid=23292514 |arxiv=1301.3145 |bibcode=2013Natur.493..381K|citeseerx=10.1.1.765.6816 |s2cid=4303714 }}</ref> The orbits of the two inner planets seems to be shaped by tidal interactions, while the evolution of ''c'' and ''d'' orbits is secular.<ref>{{cite journal | title=Extrasolar Planet Interactions | journal=Proceedings of the International Astronomical Union | volume=3 | pages=469–478 | arxiv=0801.3226v1 |date=2008 | last1=Barnes | first1=Rory | last2=Greenberg| first2=Richard | doi=10.1017/S1743921308016980 | bibcode=2008IAUS..249..469B | s2cid=17096607 }}</ref>

===Additional planets{{anchor|Upsilon Andromedae e}}===
Astronomers initially thought that a fourth planet in this system could not exist because it would have made the planetary system unstable and would have been ejected.<ref>{{cite journal | display-authors=1 | first1=Eric B. | last1=Ford | first2=Verene | last2=Lystad | first3=Frederic A. | last3=Rasio | title=Planet-planet scattering in the upsilon Andromedae system | journal=[[Nature (journal)|Nature]] | volume=434 | pages=873–876 | date=2005 | doi=10.1038/nature03427 | pmid=15829958 | issue=7035 | bibcode=2005Natur.434..873F | arxiv=astro-ph/0502441 | s2cid=119496437 }}</ref> But in 2007, an island region of stability was reported where a fourth planet could exist.<ref>{{cite journal | title=Extrasolar planet interactions | arxiv=0801.3226v1 |date=2008 | last1=Barnes | first1=Rory | last2=Greenberg| first2=Richard | journal=Proceedings of the International Astronomical Union | volume=3 | pages=469–478 | doi=10.1017/S1743921308016980 | bibcode=2008IAUS..249..469B | s2cid=17096607 }}</ref>

The existence of further planets too small or distant to detect has not been ruled out, though the presence of [[Jupiter mass|Jupiter-mass]] planets as close as 5 AU from Upsilon Andromedae A would make the system unstable.<ref>{{cite journal|last1=Lissauer |first1=J. |last2=Rivera |first2=E.|title=Stability analysis of the planetary system orbiting υ Andromedae. II. Simulations using new Lick observatory fits|journal=The Astrophysical Journal|volume=554|issue=2|pages=1141–1150|date=2001|doi=10.1086/321426|bibcode=2001ApJ...554.1141L|doi-access=free}}</ref> However, a potential fourth planet (Upsilon Andromedae e) was discovered in 2010. This planet seems to be in a 3:1 resonance with Upsilon Andromedae d.<ref name="Curiel2010"/> Subsequent studies in 2011 and 2014, while finding some evidence for a fourth planet, found large inconsistencies in the estimated orbital period of Upsilon Andromedae e depending on what dataset was used,<ref name="Tuomi2011"/> suggesting that the apparent planetary signal is more likely to be an instrumental artifact.<ref name="McArthur2014"/><ref name=Deitrick2014/>

If it exists, Upsilon Andromedae e would have a [[minimum mass]] slightly greater than [[Jupiter mass|Jupiter's]] and orbit at a similar distance as Jupiter from the Sun, at {{Val|5.2456|ul=AU}} compared to {{Val|5.2043|u=AU}} for Jupiter. Although only the [[minimum mass]] is determined since inclination is not yet known, its [[true mass]] might be much greater. It would take over a decade to orbit the star. At an eccentricity of 0.00536, the planet's orbit would be more circular than that of any of the planets in the [[Solar System]].<ref name="Curiel2010"/>

Upsilon Andromedae does not appear to have a [[circumstellar dust]] disk similar to the [[Kuiper belt]] in the Solar System.<ref>{{cite journal | last1=Trilling |first1=D. E. |last2=Brown |first2=R. H. |last3=Rivkin |first3=A. S. | title=Circumstellar dust disks around stars with known planetary companions | journal=The Astrophysical Journal | volume=529 | issue=1 | pages=499–505 | date=2000 | doi=10.1086/308280 | bibcode=2000ApJ...529..499T|s2cid=121999545 }}</ref> This may be the result of perturbations from the companion star removing material from the outer regions of the Upsilon Andromedae A system.<ref name="lowrance"/>

== See also ==
* [[51 Pegasi]]
* [[Kepler-56]]
* [[List of exoplanets discovered before 2000]] - Saffar, Samh and Majriti
* [[PSR B1257+12]]

==Notes==
{{Notelist|refs=

{{efn|name=note|The M4.5 red dwarf has the formal designation υ And D, lettered in order of discovery, in the multiple star catalogues, but is referred to as υ And B in its discovery paper.}}
}}

==References==
{{Reflist|refs=

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<ref name="Gaia EDR3 for A">{{Cite Gaia EDR3|348020482735930112}}</ref>

<ref name="Gaia EDR3 for D">{{Cite Gaia EDR3|348020242217448576}}</ref>

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}}

== External links ==
{{Commons category|Upsilon Andromedae}}
* {{cite web |url=http://www.physics.sfsu.edu/~gmarcy/planetsearch/upsand/upsand.html |title=A Triple-Planet System Orbiting Ups Andromedae |access-date=2008-06-23 |work=[[San Francisco State University]] |publisher=[[Lick Observatory]] |archive-date=2012-04-24 |archive-url=https://web.archive.org/web/20120424152305/http://www.physics.sfsu.edu/~gmarcy/planetsearch/upsand/upsand.html |url-status=dead }}
* {{cite web |url=http://www.spacedaily.com/news/extrasolar-05t.html |title=Mystery Solved: How The Orbits Of Extrasolar Planets Became So Eccentric |access-date=2008-06-23 |work=SpaceDaily |date=2005-04-14}}
* {{cite encyclopedia |url=http://www.daviddarling.info/encyclopedia/U/upsAnd.html |title=Upsilon Andromedae |access-date=2008-06-23 |encyclopedia=The Internet Encyclopedia of Science}}
* {{cite web |url=http://www.astro.uiuc.edu/~kaler/sow/upsand.html |title=Upsilon Andromedae |access-date=2008-06-23 |work=The Planet Project |url-status=dead |archive-url=https://web.archive.org/web/20080518004158/http://www.astro.uiuc.edu/~kaler/sow/upsand.html |archive-date=2008-05-18 }}
* {{cite web |url=http://www.solstation.com/stars2/ups-and.htm |title=Upsilon Andromedae 2 |access-date=2008-06-23 |work=SolStation}}
* {{cite web |url=http://cfa-www.harvard.edu/afoe/upsAnd.html |title=The Upsilon Andromedae Planetary System |access-date=2008-06-23 |work=[[Harvard-Smithsonian Center for Astrophysics]]}}
* {{cite web |url=http://www.alcyone-software.com/cgi-bin/search.pl?object=HR0458 |title=υ Andromedae |access-date=2008-06-23 |work=AlcyoneEphemeris |archive-date=2018-09-29 |archive-url=https://web.archive.org/web/20180929023249/http://www.alcyone-software.com/cgi-bin/search.pl?object=HR0458 |url-status=dead }}
* [http://webviz.u-strasbg.fr/viz-bin/VizieR-S?HR%20458 HR 0458]
* [http://webviz.u-strasbg.fr/viz-bin/VizieR-S?CCDM%20J01367%2b4125A CCDM 01367+4125]

{{Upsilon Andromedae|state=collapsed}}
{{Stars of Andromeda}}

{{Good article}}

{{Sky|01|36|47.8||41|24|20|44.1}}

{{DEFAULTSORT:Upsilon Andromedae}}
[[Category:Upsilon Andromedae| ]]
[[Category:F-type main-sequence stars]]
[[Category:Multi-star planetary systems|2]]
[[Category:Flamsteed objects|Andromedae, 50]]
[[Category:Bayer objects|Andromedae, Upsilon]]
[[Category:Hipparcos objects|007513]]
[[Category:Bright Star Catalogue objects|0458]]
[[Category:Henry Draper Catalogue objects|009826]]
[[Category:M-type main-sequence stars]]
[[Category:Durchmusterung objects|BD+40 0332]]
[[Category:Binary stars]]
[[Category:Gliese and GJ objects|0061]]
[[Category:2MASS objects|J01364784+4124200]]
[[Category:Planetary systems with three confirmed planets]]
[[Category:Stars with proper names|Titawin]]