Upsilon Andromedae d

Planetbox begin
name=Upsilon Andromedae dPlanetbox 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=F8VPlanetbox orbit
semimajor=2.54 ± 0.15
eccentricity=0.258 ± 0.032
period=1290.1 ± 8.4
ang_dist = 186.34
long_peri=279 ± 10
t_peri=2,448,827 ± 30
semi-amp=63.4 ± 1.5
semimajor_gigameter =
periastron =1.88468
periastron_gigameter =
apastron =3.19532
apastron_gigameter =
period_year =3.5321
period_megasecond = Planetbox character
mass=>3.93 ± 0.33
radius=1,039 [Estimated cite web | url=http://www.extrasolar.net/planettour.asp?StarCatId=normal&PlanetId=73 | title=Upsilon Andromedae d | work=www.extrasolar.net | accessdate=2008-09-10]
density=
gravity=90.33474
temperature=217
mass_earth =1248.954
gravity_earth = 9.211
insolation =
insolation_earth =
radius_megameter =
mass_wekagram =
radius_earth =11.631326434619Planetbox discovery
discovery_date=April 15, 1999
discovery_site= [http://exoplanets.org/esp/upsandb/upsandb.shtml exoplanets.org]
discovery_method=Radial velocity
discoverers=Butler, Marcy et al.
California and Carnegie
Planet Search
flag|USA
discovery_status=PublishedPlanetbox catalog
names=50 Andromedae dPlanetbox reference
star=Ups+And
planet=d

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

Discovery

Like the majority of known extrasolar planets, Upsilon Andromedae d 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, Upsilon Andromedae d revolves around its star in an eccentric orbit, more eccentric than that of 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] )] The orbit's semimajor axis puts the planet in the habitable zone of Upsilon Andromedae A.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]

To explain the planet's orbital eccentricity, some have proposed a close encounter with a (now lost) outer planet of Upsilon Andromedae A. The encounter would have moved Upsilon Andromedae d into an eccentric orbit closer to the star and ejected the outer planet from the system. Subsequently gravitational perturbations from Upsilon Andromedae d moved the inner planet Upsilon Andromedae c into its present eccentric orbit. [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]

A limitation of the radial velocity technique used to discover Upsilon Andromedae d is that only a lower limit on the planet's mass can be obtained. In the case of Upsilon Andromedae d, this lower limit is 3.93 times the mass of Jupiter, though depending on the inclination of the orbit, the true mass may be much greater than this value.

Preliminary astrometric measurements suggest the orbit of Upsilon Andromedae d may be 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|volume=548|pages=L57 – L60|year=2001|doi=10.1086/318927] However these measurements were later proved useful only for upper limits; [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] worthless for HD 192263 b and probably 55 Cancri c, and contradict even the inner planet u And b's inclination of >30°. The mutual inclination between c and d meanwhile is 35 degrees. A full study of this system's inclinations is forthcoming 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 it is a gas giant with no solid surface and surface gravity of over 10 times that of Earth. 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 Jupiter and an environment close to chemical equilibrium, it is predicted that its upper atmosphere will contain clouds of water, rather than the ammonia clouds typical of Jupiter. [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]

Upsilon Andromedae d lies in the habitable zone of Upsilon Andromedae A as defined both by the ability for an Earthlike world to retain liquid water at its surface and based on the amount of ultraviolet radiation received from the star. Simulations suggest that even on eccentric orbits, terrestrial planets may be able to support liquid water throughout the year. [cite journal|url=http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=105145|author=Williams, D., Pollard, D.|title=Earth-like worlds on eccentric orbits: excursions beyond the habitable zone|journal=International Journal of Astrobiology|volume=1|pages=61 – 69|year=2002|publisher=Cambridge University Press|doi=10.1017/S1473550402001064] This suggests that any large moons of Upsilon Andromedae d may be able to support extraterrestrial life.

References

ee also

* Upsilon Andromedae b
* Upsilon Andromedae c
* Eccentric Jupiter
* Planetary habitability

External links

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