47 Ursae Majoris c
2007 Schools Wikipedia Selection. Related subjects: Space (Astronomy)
| Extrasolar planet | Lists of extrasolar planets | |
|---|---|---|
| Parent star | ||
| Star | 47 Ursae Majoris | |
| Constellation | Ursa Major | |
| Right ascension | (α) | 10h 59m 28.0s |
| Declination | (δ) | +40° 25′ 49″ |
| Spectral type | G1V | |
| Orbital elements | ||
| Semimajor axis | (a) | 3.79 ± 0.24 AU |
| Eccentricity | (e) | 0.00 ± 0.12 |
| Orbital period | (P) | 2594 ± 90 d |
| Inclination | (i) | ?° |
| Longitude of periastron |
(ω) | 127 ± 56° |
| Time of periastron | (τ) | 2,451,360 ± 500 JD |
| Physical characteristics | ||
| Mass | (m) | >0.79 ± 0.13 MJ |
| Radius | (r) | ? RJ |
| Density | (ρ) | ? kg/ m3 |
| Temperature | (T) | ? K |
| Discovery information | ||
| Discovery date | 2002 | |
| Discoverer(s) | Fischer, Butler, Marcy, et al. |
|
| Detection method | Doppler Spectroscopy | |
| Discovery status | Confirmed | |
47 Ursae Majoris c is an extrasolar planet orbiting the Sun-like star 47 Ursae Majoris, making one orbital revolution every 2,594 days. The planet was discovered in 2002 and has a mass at least 79% that of Jupiter. 47 Ursae Majoris is the outermost known planet in its planetary system.
Discovery
Like the majority of known extrasolar planets, 47 Ursae Majoris c was discovered by detecting changes in its star's radial velocity caused by the planet's gravity. This was done by measuring the Doppler shift of the star's spectrum.
At the time of discovery, 47 Ursae Majoris was already known to host one extrasolar planet, designated 47 Ursae Majoris b. Further measurements of the radial velocity revealed another periodicity in the data unaccounted for by the first planet. This periodicity could be fitted by assuming a second planet, designated 47 Ursae Majoris c existed in the system with an orbital period close to 7 years. Observations of the photosphere of 47 Ursae Majoris suggest that the periodicity could not be explained by stellar activity, making the planet interpretation more likely. The planet was announced in 2002.
Orbit and mass
47 Ursae Majoris c orbits further out than the previously-known planet 47 Ursae Majoris b, at a distance comparable to that of the outer asteroid belt in our solar system. It is slightly less massive than Jupiter. The orbital eccentricity is not well constrained, but it is likely to be low. The planet is located close to the 5:2 orbital resonance with 47 Ursae Majoris b, a similar configuration to Jupiter and Saturn in our solar system. In addition, the ratio of the masses of 47 Ursae Majoris b and c is similar to the mass ratio of Jupiter and Saturn.
A limitation of the radial velocity method used to detect 47 Ursae Majoris c is that only a lower limit on the planet's mass can be obtained. This lower limit is 0.792 times the mass of Jupiter. Stability considerations suggest that the true mass of the planet is likely to lie close to this lower limit.
Characteristics
Since 47 Ursae Majoris c was detected indirectly, properties such as its radius, composition and temperature are unknown. Based on its high mass, the planet is likely to be a gas giant with no solid surface.