HIP 5158
Introduction '''HIP 5158''' is a star with a pair of orbiting substellar companions, located in the equatorial constellation of Cetus, the whale. It has the older designation CD-23 395, which is derived from the ''Cordoba Durchmusterung'' catalogue of southern stars. Based on parallax measurements, it is located 169 light years from the Sun. It has an absolute magnitude of 7.11, but at that distance the star has an apparent visual magnitude of 10.16, which is too dim to be visible to the naked eye. The system is receding with a radial velocity of 15.3 km/s, and it has a relatively high proper motion, traversing the celestial sphere at an angular rate of ·yr−1.The spectrum of HIP 5158 matches an ordinary K-type main-sequence star, an orange dwarf, with a stellar classification of K5V. The age of this star is poorly constrained, but it appears to be comparable to the Sun. It is spinning slowly with a rotation period of around 42.3 days. Based on the abundance of iron, this star appears metal rich, having concentration of heavy elements equal to 125% of solar abundance. It has 75% of the mass of the Sun and 60% of the Sun's radius. The star is radiating just 19% of the luminosity of the Sun from its photosphere at an effective temperature of 4,571 K.
Planetary system In 2009, a gas giant planet HIP 5158 b was found in orbit around the star. The quadratic drift in the radial velocities did indicate the presence of an additional outer planet in the system, which was confirmed in 2011.The large uncertainty in the mass of HIP 5158 c leaves in question whether this is an exoplanet or a brown dwarf.
See also * List of extrasolar planets
References