Upsilon Andromedae System

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Exoplanetary Scratchpad

[SysBP Img]

A nearby (44 ly) multi-star system which is the first multiplanet system found around a main sequence star. The main star around which the planets orbit is a yellow-white star somewhat younger than the sun and its companion is a red dwarf in a wide orbit. It is one of the most well studied non-transiting star systems. Roaster Planet b (0.05 au, 1.4 MJ, e=0.013) is nicknamed the Fire and Ice Planet because it is hot on one side and cold on the other. The hottest parts of the planet are near the trailing side terminator at the equator, due to high velocity winds transporting heat to the night side. This is 80deg offset from the starward pole and a much greater offset than other observed hot Jupiters. This threw astronomers off and caused them to doubt the wind-theory, though later observations of other planets have shown that winds indeed can travel fast enough to cause this. The middle planets c (0.83 au, 14 MJ, may actually be a brown dwarf star, e=0.224) and d (2.5 au, 10 MJ, e=0.26) have had their inclinations and masses determined with astrometry. They are very eccentric and highly inclined to each other (30 deg). Planet scattering was thought to be a source until the outermost planet was discovered. This is planet e (5.2 au, 1.05 MJ, e = 0.005), which is the most Jupiter-like exoplanet known, and is in 3:1 resonance with planet d. The star appears to have no Kuiper-belt like disc, perhaps due to its companion star sweeping away this material.

Upsilon Andromedae System Web Pages

Upsilon Andromedae System In the News

Planet b Discovered (1996)

Planet b Studies (1996-2005) (2000) tidal influences (2001) - clouds and atmosphere (2003) - magnetic interaction with Star (2004) - effect on Star (2005) - origin and physical history (2005) - Effects of Stellar Winds

Planet c and d Discovered (1999)

Entire System Extrapolated From Planet d (1999) (1999)

No Circumstellar Disk Found (1999)

System Stability (1999-2004) (1999) (2000) (2000) (2000) (2004)

Mass Estimation (1999-2001) (1999) (2000) (2001)

Dynamic Origin (1999-2001) (2001)

Apsidal Alignment (2001-2002) (2001) (2002) (2002)

Water MASER Detected (2002)

Star B Discovered (2002)

Star-B and Dynamics (2002)

Origin of Eccentric Planets (2002-2005) (2002) (2005)

Hubble Astrometric Studies (2003) (2003)

Theoretical Disk Structure (2003)

Search for Radio Emissions (2004-2005) (2004) (2005) (2005) (2005)

Stattered Planet? (2004-2005)

The eccentricity of the outer planets is likely due to a giant planet that was ejected from the star system.

Habitability Studies (2004) (2004)

Planet b Found to Be Half Hot Half Cold (2006)

Outer Planets Found to be Tilted 30degrees (2010)

Mysterious Hot Spot on Planet b (Oct 2010)

Jupiter Analog e Discovered (2010)

Model Using HD 209458 Data Explains Wind Source of Offset Hot Spots (2011)

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