Optical and infrared telescopes have recently been used to discover planets especially through detection of the motion of their parent stars. Most detections have been made by measuring the periodic doppler shifts of lines in the spectrum of the star as it moves around the center of mass of the star-planet system.
Planets Discovered Around Other Sunlike Stars |
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|---|---|---|---|---|
| Star | Distance to star (Earth-Sun = 1) | Orbital period | Lower limit on mass (Jupiter = 1) | Notes |
| 51 Pegasi | 0.05 | 4.3 days | 0.5 | First exoplanet, "hot Jupiter" |
| 47 Ursae Majoris | 2.1 | 1103 days | 2.4 | |
| 70 Virginis | ecc. orbit | 116.7 days | 6.6 | Possible brown dwarf |
| 55 Cancri | 0.11 | 14.76 days | 0.8 | "Hot Jupiter" |
| 55 Cancri | >5 | unknown | >5 | |
| HD 114762 | ecc. orbit | 84.01 days | 10 | Possible brown drawf |
| Tau Bootis | 0.0047 | 3.31 days | 3.7 | "Hot Jupiter" |
| Upsilon Andromedae | 0.054 | 4.61 days | 0.6 | "Hot Jupiter" |
| Lalande 21185 | 2.2 | 5.8 days | 0.9 | Astrometric detection |
| Lalande 21185 | 11 | 30 years | 1.1 | Astrometric detection (uncertain) |
| Source: Science, Vol. 273, July 26, 1996 | ||||
The pulsar called PSR 1257+12 also has an orbiting planetary system. This was the FIRST star around which exoplanets were discovered (contrary to popular misconception, exoplanets were discovered by radio astronomers!).
Suggested readings:
"The Planet of 51 Pegasi", MacRobert, A.M. and Roth, J. 1996, Sky and Telescope January 1996 pp. 38-40.
"Extrasolar Planets", Boss, Alan P. 1996, Physics Today September 1996 pp. 33-38.
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