1) Sirius ⇒ Sirius is a star system and the brightest star in the Earth's night sky. 2) Proximacentauri ⇒ Proxima Centauri a small low – mass star, about 4.25[9] light – years from the Sun in the constellation of Centaurus. 3) Deimos ⇒ Deimos is the smaller and outer of the two natural satellites of the planet Mars, the other being Phobos. Deimos has a mean radius of 6.2 km and takes 30.3 hours to orbit Mars. 4) Alpha centauri ⇒ Alpha Centauri (α Centauri, abbreviated Alpha Cen, α Cen) is the closest star system to the Solar System, being 4.37 light – years (1.34 pc) from the Sun. It consists of three stars : Alpha Centauri A and Alpha Centauri B, which form the binary star Alpha Centauri AB (also named Rigil Kentaurus), and a small and faint red dwarf, Alpha Centauri C (also named Proxima Centauri) Therefore, Deimos is odd one among given alternatives.