EntityQ50668· pop 36· linked from 253 articles

55 Cancri e

extrasolar planet

Key facts

Discovered by: McArthur et al.
Discovery site: McDonald Observatory
Discovery date: 2004 (announced), 2003–2004 (discovery data)
Detection method: Radial velocity
Apastron: 0.01617 AU (2,419,000 km)
Periastron: 0.01464 AU (2,190,000 km)
Semi major axis: 0.01544 ± 0.00005 AU (2,309,800 ± 7,500 km)
Eccentricity: 0.05 ± 0.03
Orbital period sidereal: 0.736 546 25 (15) d , 17.67711 h
Inclination: 83.59 , − 0.44
Time of periastron: 2,449,999.83643 ± 0.0001
Argument of periastron: 86.0 , − 33.4
Semi amplitude: 6.02 , − 0.23
Star: 55 Cancri A
Mean radius: 1.875 ± 0.029 R 🜨
Mass: 7.99 , − 0.33 M 🜨
Mean density: 6.66 , − 0.40 g cm
Surface gravity: 2.273 g

via Wikipedia infobox

Article

55 Cancri Ae (abbreviated 55 Cnc Ae), officially named Janssen (/ˈdʒænsən/ ), is an exoplanet orbiting a Sun-like host star, 55 Cancri A. The mass of the exoplanet is about eight Earth masses and its diameter is about twice that of the Earth. 55 Cancri Ae was discovered in data taken during 2003–2004 and announced in 2004, thus making it the first super-Earth discovered around a main sequence star, predating Gliese 876 d by a year. It is the innermost planet in its planetary system, taking less than 18 hours to complete an orbit. However, until the 2010 observations and recalculations, this planet had been thought to take about 2.8 days to orbit the star.

Due to its proximity to its star, 55 Cancri Ae is extremely hot, with temperatures on the day side exceeding 3,000 Kelvin. The planet's thermal emission is observed to be variable, possibly as a result of volcanic activity. It has been proposed that 55 Cancri Ae could be a carbon planet.