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Upsilon Andromedae b

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Template:Planetbox begin Template:Planetbox star Template:Planetbox orbit Template:Planetbox character Template:Planetbox discovery Template:Planetbox catalog Template:Planetbox end Upsilon Andromedae b (occasionally referred to as Upsilon Andromedae Ab to distinguish it from the red dwarf star Upsilon Andromedae B) is an extrasolar planet orbiting the Sun-like star Upsilon Andromedae A every 4.62 days. Discovered in 1996 by Geoffrey Marcy and R. Paul Butler, it was one of the first hot Jupiters to be discovered. Upsilon Andromedae b is the innermost known planet in its planetary system.

Discovery

Like the majority of known extrasolar planets, 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 was announced in 1996, together with 55 Cancri b and the planet orbiting Tau Boötis.

Orbit and mass

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 our Sun. The planet takes 4.617 days to complete an orbit, with a semimajor axis of 0.059 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. In the case of Upsilon Andromedae b, this lower limit is 69% of the mass of Jupiter, though depending on the inclination of the orbit, the true mass may be much greater.

Characteristics

Given the planet's high mass, it is likely that Upsilon Andromedae b is a gas giant with no solid surface. Since the planet has only been detected indirectly, properties such as its radius, composition and temperature are unknown. Assuming that the planet is similar to Jupiter in composition and that its environment is close to chemical equilibrium, Upsilon Andromedae b is predicted to have clouds of silicates and iron in its upper atmosphere.

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

References

  1. Butler, R.; et al. (1997). "Three New 51 Pegasi-Type Planets". The Astrophysical Journal. 474: L115 – L118. {{cite journal}}: Explicit use of et al. in: |author= (help)
  2. "A Triple-Planet system around Ups Andromedae". California & Carnegie Planet Search. 2003. {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  3. Sudarsky, D.; et al. (2003). "Theoretical Spectra and Atmospheres of Extrasolar Giant Planets". The Astrophysical Journal. 588 (2): 1121–1148. {{cite journal}}: Explicit use of et al. in: |author= (help)
  4. Barnes, J., O'Brien, D. (2002). "Stability of Satellites around Close-in Extrasolar Giant Planets". The Astrophysical Journal. 575 (2): 1087–1093.{{cite journal}}: CS1 maint: multiple names: authors list (link)

See also

External links

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