570 D, this brown dwarf is thought to have a surface temperature of about . When 54 Piscium B was directly imaged by NASA's Spitzer Space Telescope, it was shown that the brown dwarf had a projected separation of around 476 astronomical units from the primary star. 54 Piscium B was the first brown dwarf to be detected around a star with an already known extrasolar planet (based on radial velocity surveys). Planetary system The star rotates at an inclination of 83 degrees relative to Earth. On January 16, 2003, a team of astronomers (led by Geoff Marcy) announced the discovery of an extrasolar planet (named 54 Piscium b) around 54 Piscium. The planet has been estimated to have a mass of only 20 percent that of Jupiter (making the planet around the same size and mass of Saturn). The planet orbits its sun at a distance of 0.28 astronomical units (which would be within the orbit of Mercury), which takes approximately 62 days to complete. It has been assumed that the planet shares the star's inclination and so has real mass close to its minimum mass; however, several "hot Jupiters" are known to be oblique relative to the stellar axis. The planet has a high eccentricity of about 0.65. The highly elliptical orbit suggested that the gravity of an unseen object farther away from the star was pulling the planet outward. That cause was verified with the discovery of the brown dwarf within the system. The orbit of an Earth-like planet would need to be centered within 0.68 AU (around the orbital distance of Venus), which in a Keplerian system means a 240-day orbital period. In a later simulation with the brown dwarf, 54 Piscium b's orbit "sweeps clean" most test particles within 0.5 AU, leaving only asteroids "in low-eccentricity orbits near the known planet's apastron distance, near the 1:2 mean-motion resonance". Also, observation has ruled out Neptune-class or heavier planets with a period of one year or less; which still allows for Earth-sized planets at 0.6 AU or more. A two planet fit to the radial velocities with two circular planets in a 2:1 orbital resonance is possible however it does not significantly improve the solution, and therefore does not justify the additional complexity. See also 107 Piscium 109 Piscium Delta Trianguli Upsilon Andromedae References External links K-type main-sequence stars Piscium, 54 Maunder Minimum Suspected variables Brown dwarfs