Upsilon Andromedae c

Planetbox begin
name=Upsilon Andromedae c
Planetbox star
star=Upsilon Andromedae A
constell=Andromeda
RA=RA|01|36|47.8
DEC=DEC|+41|24|20
dist_ly = 43.9
dist_pc = 13.5
class=F8V
Planetbox orbit
semimajor = 0.830 ± 0.048
eccentricity = 0.262 ± 0.021
period = 241.23 ± 0.30
ang_dist = 61.618
long_peri = 245.5 ± 5.3
t_peri = 2,450,158.1 ± 4.5
semi-amp = 55.6 ± 1.7
Planetbox character
mass = >1.97 ± 0.17
radius=1.024 [Estimated, cite web | url=http://www.extrasolar.net/planettour.asp?StarCatId=normal&PlanetId=72 | title=Upsilon Andromedae c | work=www.extrasolar.net | accessdate=2008-10-09]
density=
gravity=46.61864732
temperature=
mass_earth =626.066
gravity_earth =4.753779
insolation =
insolation_earth =
radius_megameter =
mass_wekagram =
radius_earth =11.4634
Planetbox discovery
discovery_date = April 15, 1999
discovery_site= [http://exoplanets.org/esp/upsandb/upsandb.shtml exoplanets.org/]
discovery_method = Radial velocity
discoverers = Marcy et al.
California and Carnegie
Planet Search

flag|USA
discovery_status=Published
Planetbox catalog
names=50 Andromedae c
Planetbox reference
star=Ups+And
planet=c

Upsilon Andromedae c is an extrasolar planet orbiting the Sun-like star Upsilon Andromedae A every 241.2 days. Its discovery in April 1999 by Geoffrey Marcy and R. Paul Butler made Upsilon Andromedae the first known star (excluding the pulsar PSR 1257+12) to host a multiple-planet planetary system. Upsilon Andromedae c is the second known planet in order of distance from its star.

Discovery

Like the majority of known extrasolar planets, Upsilon Andromedae c was detected by measuring variations in its star's radial velocity as a result of the planet's gravity. This was done by making precise measurements of the Doppler shift of the spectrum of Upsilon Andromedae A. At the time of discovery, Upsilon Andromedae A was already known to host one extrasolar planet, the hot Jupiter Upsilon Andromedae b, however by 1999 it was clear that the inner planet could not explain the velocity curve.

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 new planets were designated Upsilon Andromedae c and Upsilon Andromedae d.

Orbit and mass

Like the majority of long-period extrasolar planets, the orbit of Upsilon Andromedae c is eccentric, more so than any of the major planets in our solar system (including Pluto). [cite journal|url=http://www.journals.uchicago.edu/doi/abs/10.1086/504701|author=Butler, R. et al.|title=Catalog of Nearby Exoplanets|journal=The Astrophysical Journal|volume=646|pages=505 – 522|year=2006|doi=10.1086/504701 ( [http://exoplanets.org/planets.shtml web version] )] If placed in our solar system, Upsilon Andromedae c would lie between the orbits of Earth and Venus.

The high orbital eccentricity may be the result of gravitational perturbations from the planet Upsilon Andromedae d. Simulations suggest that the orbit of Upsilon Andromedae c returns to its original circular state roughly once every 6,700 years. [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]

One proposal is that interactions between Upsilon Andromedae d and a (now lost) outer planet moved Upsilon Andromedae d into an orbit closer to the star, where it gradually caused the orbit of Upsilon Andromedae c to become eccentric. 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]

A limitation of the radial velocity method used to detect Upsilon Andromedae c is that only a lower limit on the planet's mass can be obtained. For Upsilon Andromedae c, this lower limit is 1.97 times the mass of Jupiter, though depending on the inclination of the planet's orbit, the true mass may be much greater. The mutual inclination between c and d is 35 degrees, and full publication is expected in 2008. [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. ]

Characteristics

Given the planet's high mass, it is likely that Upsilon Andromedae c is a gas giant with no solid surface. Since the planet has only been detected indirectly through observations of its star, properties such as its radius, composition and temperature are unknown. Assuming a composition similar to that of Jupiter and that its environment is close to chemical equilibrium, it is predicted that the upper atmosphere of Upsilon Andromedae c is cloudless. [cite journal|url=http://adsabs.harvard.edu/abs/2003ApJ...588.1121S|author=Sudarsky, D. et al.|title=Theoretical Spectra and Atmospheres of Extrasolar Giant Planets|journal=The Astrophysical Journal|volume=588|issue=2|pages=1121 – 1148|year=2003|doi=10.1086/374331]

References

ee also

* Upsilon Andromedae b
* Upsilon Andromedae d
* Eccentric Jupiter

External links

* [http://simbad.u-strasbg.fr/sim-id.pl?Ident=%2A+ups+And+c SIMBAD: * ups And c -- Extra-solar Planet Candidate]
* [http://exoplanet.eu/planet.php?p1=Ups+And&p2=c The Extrasolar Planets Encyclopaedia: Notes for Planet Ups And c]


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