Upsilon Andromedae

Upsilon Andromedae (or υ Andromedae) is a star, approximately 44 light-years from Earth, and approximately 3 billion years old, two thirds the age of our Sun. Viewed from Earth, Upsilon Andromedae is in the Andromeda Constellation, and is about 10 degrees east of the Andromeda Galaxy.

Upsilon Andromedae was the first star determined to have more than one extrasolar planet. So far, three such objects have been discovered within the system; all three are believed to be gas giants.

Table of contents

1 The Three Extrasolar Planets of Upsilon Andromedae
2 History of Discovery
3 External links

The Three Extrasolar Planets of Upsilon Andromedae

Upsilon Andromedae b:
- Distance from UA: 0.06AU
- Mass: 0.71 M_J
- Orbital Period: 4.6 days
Upsilon Andromedae c:
- Distance from UA: 0.83AU
- Mass: 2.11 M_J
- Orbital Period: 242 days
\'Upsilon Andromedae d:'
- Distance from UA: 2.5AU
- Mass: 4.61 M_J
- Orbital Period: 3.5 years

History of Discovery

The inner planet (b) was discovered in 1996 and announced in January of 1997 by Geoffrey Marcy and R. Paul Butler, both astronomers at San Francisco State University (SFSU). Because of its closeness to the parent star, it induced a large wobble which was detected relatively easily. However, some additional wobble in the star remained unexplained, and it was suggested there might be a second planet in orbit. In the end, astronomers at both SFSU and the Harvard-Smithsonian Center for Astrophysics independently concluded that, in fact, a 3-planet model best fit the data. These results were announced on April 15, 1999.

The existence of further planets too small to detect has not been ruled out.