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HD 217107 is a yellow subgiant star in the constellation Pisces. HD 217107 was a Sun-like star, and now is older and is finishing up it's hydrogen fusion in its core and is about to swell up becoming a red giant.

The Hipparcos astrometric satellite gives the star an unlikely parallax of 50.71 mas (corresponds a distance of 64 light years); it would be dimmer than the Sun. A value of ~120 light years is probably more accurate. In that case the star would be about four times brighter than the Sun. The star may be visible to the unaided eye under exceptionally good conditions, but usually binoculars are needed.

As of 2005, HD 217107 is known to have two extrasolar planets orbiting it.

HD 217107 b

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HD 217107 b is an a hot jupiter extrasolar planet orbiting it's sun every seven days. It is the inner planet and was discovered by the California and Carnegie Planet Search team in 1998. As with the majority of extrasolar planet discoveries so far, it was found by the radial velocity method.

HD 217107 b is somewhat more massive then Jupiter, and orbits the star in a so-called "torch orbit". Its mean distance from the star is less than one fifth Mercury's distance from the Sun. Although most very short orbits are circular due to tidal effects between the star and the planet, this one has a slightly elliptical orbit.

HD 217107 c

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HD 217107 c is a Jupiter-like extrasolar planet orbiting it's sun every nine years. The planet was proposed in 1999 but was unconfirmed. But in 2005, radial velocity studies of the star indicated another, more distant and massive companion orbiting the star. HD 217107 c was finaly confirmed six years after it was proposed. However, its mass and orbital parameters remain highly uncertain.

External links

• SIMBAD: HD 217107
• Extrasolar Planets Encyclopaedia: HD 217107 + HD 217107 b + HD 217107 c
• Extrasolar Visions: HD 217107 + HD 217107 b + HD 217107 c
• SolStation: HD 217107 / HR 8734

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• Pisces constellation
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• HIP objects
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