Upsilon Andromedae

Starbox begin
name = Upsilon Andromedae Starbox observe
epoch = J2000.0
constell = Andromeda
ra = 01^h 36^m 47.8^s
dec = +41° 24' 20"
appmag_v =4.09 Starbox character
class = F8V
r-i = 0.30
v-r = 0.30
b-v = 0.54
u-b = 0.06
variable = Starbox astrometry
radial_v = -28.9 ± 0.9
prop_mo_ra = -172.57 ± 0.52
prop_mo_dec = -381.03 ± 0.45
parallax = 73.97
p_error = 0.19
parallax_footnote = cite web|url=http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/311/hip2&recno=7499|title=HIP 7513|work=Hipparcos, the New Reduction|author=van Leeuwen, F.|year=2007|accessdate=2008-08-17]
absmag_v = 3.44Starbox detail
mass = 1.28
radius = 1.6
density = 440
gravity = 3.83
luminosity = 3.4
temperature = 6,095
metal = 100%
rotation = ~10 days
age = 3.3 × 10⁹
rotational_velocity =~8 Starbox catalog
names = 50 Andromedae, Gl 61, HR 458, BD +40°332, HD 9826, LTT 10561, GCTP 331.00, SAO 37362, FK5 1045, GC 1948, CCDM 01367+4125, WDS 01368+4124A, HIP 7513Starbox reference
Simbad=HD+9826
ARICNS =

Upsilon Andromedae (υ Andromedae / υ And) is a binary star located approximately 44 light-years away in the constellation Andromeda. The primary star (Upsilon Andromedae A) is a yellow dwarf star that is somewhat younger than the Sun. The second star in the system (Upsilon Andromedae B) is a red dwarf located in a wide orbit.

As of 2008, three confirmed extrasolar planets are known in orbit around the primary star. All three are likely to be Jovian planets that are comparable to Jupiter. Upsilon Andromedae was both the first multiple-planet planetary system to be discovered around a main sequence star, and the first multiple-planet system known in a multiple star system.

History

Upsilon Andromedae A is ranked 21st in the list of top 100 target stars for the NASA Terrestrial Planet Finder mission. Note NASA has cancelled this mission indefinitely, due to funding limitations (See wikipedia article Terrestrial Planet Finder) [cite web|url=http://sco.stsci.edu/tpf_top100/detail.php?starchoice=7513|title=#12 HIP 7513|work=TPF-C Top 100|accessmonthday=5 July|accessyear=2006]

Distance and visibility

Upsilon Andromedae is located fairly close to our solar system: the parallax of Upsilon Andromedae A was measured by the Hipparcos astrometry satellite as 73.97 milliarcseconds, corresponding to a distance of 13.52 parsecs (44.1 light years). 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.

System components

Upsilon Andromedae A is a yellow-white dwarf of spectral type F8V, similar to our Sun but rather younger, more massive and luminous. According to its entry in the Geneva-Copenhagen survey, the star is around 3.3 thousand million years old, and has a similar proportion of iron relative to hydrogen as the Sun. [cite web|url=http://vizier.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=V/117/table1&recno=970|title=Record 970|work=Geneva-Copenhagen Survey of Solar neighbourhood|author=Nordstrom "et al."|year=2004|accessmonthday=5 July|accessyear=2006] At around 1.3 solar masses, it will have a shorter lifetime than our 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.cite journal|url=http://adsabs.harvard.edu/abs/2005astro.ph.12291B|author=Buccino, A. "et al."|title=Ultraviolet Radiation Constraints around the Circumstellar Habitable Zones|journal=Icarus|volume=183|issue=2|pages=491–503|year=2006|doi=10.1016/j.icarus.2006.03.007]

Upsilon Andromedae B is a red dwarf of spectral type M4.5V located at a distance (in the plane of the sky) 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 us and the Upsilon Andromedae stars is unknown, so this value is a minimum separation. It was discovered in 2002 in data collected as part of the Two Micron All Sky Survey.cite journal|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2002ApJ...572L..79L&db_key=AST&nosetcookie=1|author=Lowrance, P. "et al."|title=A Distant Stellar Companion in the υ Andromedae System|journal=The Astrophysical Journal Letters |volume=572|issue=1|pages=L79–L81|year=2002|doi=10.1086/341554] The star is less massive and far less luminous than our 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. [cite web|url=http://ad.usno.navy.mil/wds/|title=Washington Double Star Catalog - Current Version|author=Mason, D. "et al."|accessmonthday=5 July|accessyear=2006]

Planetary system

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. [cite journal | url=http://www.journals.uchicago.edu/doi/full/10.1086/310444|author=Butler, R. "et al." | title=Three New 51 Pegasi-Type Planets | journal=The Astrophysical Journal Letters | volume=474 |year=1997 | issue=2 | pages=L115–L118 | doi=10.1086/310444 ] 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. [cite journal|url=http://www.citebase.org/cgi-bin/citations?id=oai:arXiv.org:astro-ph/0411655|title=Hot Jupiters and Hot Spots: The Short- and Long-term Chromospheric Activity on Stars with Giant Planets|author=Shkolnik, E. "et al."|journal=The Astrophysical Journal|volume=622|year=2005|pages=1075–1090|doi=10.1086/428037]

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. [cite journal|url=http://www.journals.uchicago.edu/doi/full/10.1086/308035|author=Butler, R. "et al."|title=Evidence for Multiple Companions to υ Andromedae|journal=The Astrophysical Journal|volume=526|pages=916–927|year=1999|doi=10.1086/308035 ] The two outer planets were designated Upsilon Andromedae c and Upsilon Andromedae d in order of increasing distance from the star. Both of the two outer planets are in more eccentric orbits than any of the planets in our solar system (including Pluto). [cite journal|doi= 10.1086/504701|author=Butler, R. "et al."|title=Catalog of Nearby Exoplanets|journal=The Astrophysical Journal|volume=646|pages=505–522|year=2006 ( [http://exoplanets.org/planets.shtml web version] )] The outermost planet resides in the system's habitable zone.

The system is not coplanar. The mutual inclination between c and d is 35 degrees. [cite journal | journal=American Astronomical Society Meeting Abstracts | volume=211| title=Planet Masses in the Upsilon Andromadae system determined with the HST Fine Guidance Sensors |year=2007 | author=McArthur, B., Benedict, G. F., Bean, J., & Martioli, E. ] In 2001, preliminary astrometric measurements suggested the orbit of the outermost planet is inclined at 155.5° to the plane of the sky. [cite journal|url=http://www.journals.uchicago.edu/doi/full/10.1086/318927|title=Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions|author=Han, I. "et al."|journal=The Astrophysical Journal Letters| volume=548 |pages=L57–L60|year=2001|doi=10.1086/318927 ] But subsequent investigation of the data reduction techniques used suggests that the Hipparcos measurements are not precise enough to adequately characterise the orbits of substellar companions. [cite journal|url=http://adsabs.harvard.edu/abs/2001A%26A...372..935P|title=Screening the Hipparcos-based astrometric orbits of sub-stellar objects|author=Pourbaix, D. and Arenou, F.|journal=Astronomy and Astrophysics|volume=372|pages=935–944|year=2001|doi=10.1051/0004-6361:20010597] Astrometry of the innermost planet, meanwhile, constrained its inclination to 30-90 degrees. Full publication is expected in 2008. [cite journal | title=The υ Andromedae Planetary System - Hubble Space Telescope Astrometry and High-precision Radial Velocities |author=Benedict, George F.; McArthur, B. E.; Bean, J. L. |year=2007 | journal=Bulletin of the American Astronomical Society |volume=38 |pages=185 Announced American Astronomical Society Meeting 210, #78.02] 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. [cite journal|url=http://simbad.u-strasbg.fr/cgi-bin/cdsbib?2001ApJ...554.1141L|author=Lissauer, J., Rivera, E.|title=Stability analysis of the planetary system orbiting υ Andromedae. II. Simulations using new Lick observatory fits|journal=The Astrophysical Journal|volume=554|pages=1141–1150|year=2001|doi=10.1086/321426]

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. [cite journal|url=http://simbad.u-strasbg.fr/cgi-bin/cdsbib?2005Natur.434..873F|author=Ford, E. "et al."|title=Planet-planet scattering in the upsilon Andromedae system|journal=Nature|volume=434|pages=873–876|year=2005|doi=10.1038/nature03427] If so the rogue planet would have had to eject immediately; it is unclear how likely this situation might be. Other models are possible. [cite arXiv | title=Extrasolar Planet Interactions | author=Rory Barnes & Richard Greenberg | eprint=0801.3226v1 |class=astro-ph |year=2008]

Upsilon Andromedae does not appear to have a circumstellar dust disk similar to the Kuiper belt in our solar system. [cite journal|url=http://simbad.u-strasbg.fr/cgi-bin/cdsbib?2000ApJ...529..499T|author=Trilling, D. "et al."|title=Circumstellar dust disks around stars with known planetary companions|journal=The Astrophysical Journal|volume=529|pages=499–505|year=2000|doi=10.1086/308280] This may be the result of perturbations from the companion star removing material from the outer regions of the Upsilon Andromedae A system.PlanetboxOrbit begin
name = Upsilon Andromedae APlanetboxOrbit
exoplanet = b
mass = >0.687 ± 0.058
period = 4.617113 ± 0.000082
semimajor = 0.0595 ± 0.0034
eccentricity = 0.023 ± 0.018PlanetboxOrbit
exoplanet = c
mass = >1.97 ± 0.17
period = 241.23 ± 0.30
semimajor = 0.830 ± 0.048
eccentricity = 0.262 ± 0.021PlanetboxOrbit
exoplanet = d
mass = >3.93 ± 0.33
period = 1290.1 ± 8.4
semimajor = 2.54 ± 0.15
eccentricity = 0.258 ± 0.032

See also

*51 Pegasi
*Binary star
*Extrasolar planet
*List of stars with confirmed extrasolar planets
*PSR 1257+12
*Solar analog

References

External links

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* [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]
* [http://simbad.u-strasbg.fr/simbad/sim-id?Ident=%2A%20ups%20And%20e Hypothetic object ups And e]
* [http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ Extrasolar Planet Interactions] by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona
* [http://planetquest1.jpl.nasa.gov/atlas/atlas_skymap.cfm?Star=1 Sky map]