HD 217107
HD 217107 is a yellow sub-giant that can be found in the constellation Pisces . Although the star is significantly older than the sun , it has roughly the same mass . The star is orbited by two planets , one of which takes only seven days to orbit its sun, while the other takes eight years to orbit.
The star
From an astronomical point of view, the star is very close to our sun. Its distance is only 64 light years , which can be viewed as the closer environment of our sun. However, since its apparent magnitude is only 6.17 mag, it is only possible to see it with the naked eye under optimal conditions.
Spectroscopic investigations show that the star is of the spectral type G7 or G8 and thus has a surface temperature of approx. 5000 Kelvin . The age of the star is estimated to be 7.7 billion years, which is quite a long when compared to the Sun's 4.6 billion years. The star has now fused most of its hydrogen and is moving away from the main sequence .
Planetary system
By measuring the radial velocity in 1998, it was found that there is a fluctuation with a 7.1 day period. This was attributed to the presence of an orbital companion, which had to have a minimum mass that is just above Jupiter's mass. This companion was named HD 217107 b . Planets with such a short orbital period usually have almost circular orbits, but HD 217107 b was found to have an eccentricity, the cause of which could be a second companion of the star, which had to orbit the star at a distance of a few AU. Long-term observations have shown that the star has a further deviation in radial velocity that shows a period of eight years. This observation confirmed the assumption of a second planet, its minimum mass could be limited to two Jupiter masses, the radius of its major semi-axis is four AU . This second planet was named HD 217107c .
credentials
- ↑ SIMBAD: HD217107 (URL last accessed on May 4, 2006)
- ↑ Fischer et al. : Planetary Companions to HD 12661, HD 92788, and HD 38529 and Variations in Keplerian Residuals of Extrasolar Planets . In: The Astrophysical Journal . 551, No. 2, 2002, pp. 1107-1118. ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ↑ Vogt et al. : Five New Multicomponent Planetary Systems . In: The Astrophysical Journal . 632, No. 1, 2005, pp. 638-658. ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
