Cepheus (constellation)
Cepheus is a constellation in the far northern sky, named after Cepheus, a king of Aethiopia in Greek mythology. It is one of the 48 constellations listed by the second century astronomer Ptolemy, and it remains one of the 88 constellations in the modern times.
| Constellation | |
| Abbreviation | Cep |
|---|---|
| Genitive | Cephei |
| Pronunciation | /ˈsiːfiəs/ or /ˈsiːfjuːs/; genitive /ˈsiːfiaɪ/ |
| Symbolism | the King/King Cepheus |
| Right ascension | 20h 01m 56.4481s–09h 03m 19.7931s |
| Declination | 88.6638870°–53.3532715° |
| Area | 588 sq. deg. (27th) |
| Main stars | 7 |
| Bayer/Flamsteed stars | 43 |
| Stars with planets | 1 |
| Stars brighter than 3.00m | 1 |
| Stars within 10.00 pc (32.62 ly) | 3 |
| Brightest star | α Cep (Alderamin) (2.45m) |
| Messier objects | 0 |
| Meteor showers | 0c |
| Bordering constellations | Cygnus Lacerta Cassiopeia Camelopardalis Draco Ursa Minor |
| Visible at latitudes between +90° and −10°. Best visible at 21:00 (9 p.m.) during the month of November. | |
The constellation's brightest star is Alpha Cephei, with an apparent magnitude of 2.5. Delta Cephei is the prototype of an important class of star known as a Cepheid variable. RW Cephei, an orange hypergiant, together with the red supergiants Mu Cephei, MY Cephei, VV Cephei, and V354 Cephei are among the largest stars known. In addition, Cepheus also has the hyperluminous quasar S5 0014+81, which hosts an ultramassive black hole in its core, reported at 40 billion solar masses, about 10,000 times more massive than the central black hole of the Milky Way, making this among the most massive black holes currently known.