Want to stay on top of all the space news? Follow @universetoday on TwitterAlrai, also known as Gamma Cephei, Errai, and Er Rai, is a binary star system that is a mere 45 light years away in the Cepheus constellation. It has an apparent magnitude of 3.22 and has a stellar class of K1III-IV which means that it is a orange subgiant. The star is thought to be 6.6 billion years old.
Alrai can be seen with the naked eye and is the star that should eventually become the North Star due to the axial precession of the Earth. It will be closer to the northern celestial pole than Polaris around the year 3000 AD and will be at its closest around the year 4000 AD. After that Iota Cehpei, or Alvahet, will take its place as the North Star at some time around the year 5200 AD.
Alrai has a companion star that has a mass approximately 0.409 times that of our Sun. Gamma Cephei B is of stellar mass and is thought to be of similar age to the primary. It is believed to be a red dwarfof class M4. That makes it 6.2 degrees of magnitude fainter than the K-type primary star. Another star, B Ophiuchi is some times referred to by the same name. B Ophiuchi is truly named Cebalrai.
A Canadian team announced that they found a planet orbiting Alrai in 1988. That finding was backed up by another team in 1989. The finding was later confused. It would have been the first confirmed extrasolar planet and its ostensible discovery was based on the same radial velocity technique later used successfully by others. The claim was retracted in 1992 because the quality of the data was not good enough to establish discovery. In 2002 evidence of the planet was considerably strengthened by new measurements at the McDonald Observatory.
There are many interesting facts about Alrai. The finding of a planet is just one. This link takes you to a good article about the star. Here on Universe Today we have a great article about the entire Cepheus constellation. Astronomy Cast offers a good episode about binary stars just like Alrai.