Cassiopeia is a constellation and asterism in the northern sky named after the vain queen Cassiopeia, mother of Andromeda, in Greek mythology, who boasted about her unrivaled beauty. Cassiopeia was one of the 48 constellations listed by the 2nd-century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is easily recognizable due to its distinctive 'W' shape, formed by five bright stars.
Eta Cassiopeiae is a binary star system in the northern constellation of Cassiopeia. Its binary nature was first discovered by William Herschel in August 1779. Based upon parallax measurements, the distance to this system is 19.42 light-years from the Sun. The two components are designated Eta Cassiopeiae A and B.
Alpha Cassiopeiae or α Cassiopeiae, also named Schedar, is a second-magnitude star in the northern constellation of Cassiopeia. Though listed as the "alpha star" by Johann Bayer, α Cas's visual brightness closely matches the 'beta' (β) star in the constellation and it may appear marginally brighter or dimmer, depending on which passband is used. However, recent calculations from NASA's WISE telescope confirm that α Cas is the brightest in Cassiopeia, with an apparent magnitude of 2.240. Its absolute magnitude is 18 times greater than β Cas, and it is located over four times farther away from the Sun.
Gamma Cassiopeiae, Latinized from γ Cassiopeiae, is a bright star at the center of the distinctive "W" asterism in the northern circumpolar constellation of Cassiopeia. Although it is a fairly bright star with an apparent visual magnitude that varies from 1.6 to 3.0, it has no traditional Arabic or Latin name. It sometimes goes by the informal name Navi. It was observed 1866 by Angelo Secchi, the first star ever observed with emission lines. It is now considered a Be star.
50 Cassiopeiae is a white star in the northern constellation of Cassiopeia. In the past, it had been misidentified as a suspected nebula, and given the number NGC 771. The star is visible to the naked eye, having an apparent visual magnitude of +3.95. Based upon an annual parallax shift of 20.76 mas, it is located 157 light years away. It is moving closer, having a heliocentric radial velocity of −18 km/s, and will approach to within 82 ly in 1.879 million years.
Kappa Cassiopeiae is a star in the constellation Cassiopeia.
Omicron Cassiopeiae is a triple star system in the constellation Cassiopeia. It is approximately 700 light-years from Earth, based on its parallax. It is visible to the naked eye with a slightly variable apparent magnitude of about 4.5.
Sigma Cassiopeiae is a binary star in the constellation Cassiopeia. It is 1,200 to 1,400 light years from Earth and has a combined apparent magnitude of +4.88.
Nu Cassiopeiae, Latinized from ν Cassiopeiae, is a solitary star in the northern constellation of Cassiopeia. With an apparent visual magnitude of +4.89, it is a faint star but visible to the naked eye. Based upon an annual parallax shift of 7.92 mas as seen from Earth, this star is located around 410 light years from the Sun. Cowley et al. (1969) catalogued this star with a stellar classification of B9 III, indicating it has the spectrum of an evolved B-type giant star. However, Palmer et al. (1968) assigned it a class of B8 V, which would instead suggest it is an ordinary B-type main-sequence star.
Pi Cassiopeiae, Latinized from π Cassiopeiae, is a close binary star system in the constellation Cassiopeia. It is visible to the naked eye with an apparent visual magnitude of +4.949. Based upon an annual parallax shift of 18.63 mas as seen from Earth, this system is located about 175 light years from the Sun.
Phi Cassiopeiae is a multiple star in the constellation Cassiopeia with a combined apparent magnitude of +4.95. The two brightest components are A and C, sometimes called φ1 and φ2 Cas. φ Cas A is an F0 bright supergiant of magnitude 4.95 and φ Cas C is a 7.08 magnitude B6 supergiant at 134".
4 Cassiopeiae is a red giant in the northern constellation of Cassiopeia, located approximately 790 light-years away from the Sun. It is visible to the naked eye as a faint, red-hued star with a baseline apparent visual magnitude of 4.96. At the distance of this system, its visual magnitude is diminished by an extinction of 0.56 due to interstellar dust. This system is moving closer to the Earth with a heliocentric radial velocity of −39 km/s.
Omega Cassiopeiae is a binary star system in the northern constellation of Cassiopeia. It has a combined apparent visual magnitude of +4.99, which means it is a faint star but visible to the naked eye. Based upon an annual parallax shift of 4.65 mas as seen from Earth, this system is located roughly 730 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction of 0.16 due to interstellar dust.
42 Cassiopeiae is a possible binary star system in the northern circumpolar constellation of Cassiopeia. It is visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of +5.18. The system is located approximately 291 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +7 km/s.
R Cassiopeiae is a variable star in the northern constellation of Cassiopeia. It is located approximately 574 light years distant from the Sun, but is drifting closer with a radial velocity of −23 km/s. This is a pulsating Mira-type variable star with a brightness varies from magnitude +4.4 down to +13.5 with a period of 433.6 days. At its maximum, R Cassiopeiae is visible to the naked eye as a faint, red-hued star.
6 Cassiopeiae is a white hypergiant in the constellation Cassiopeia, and a small-amplitude variable star.
AR Cassiopeiae is a variable star in the constellation of Cassiopeia. It is thought to be a member of a septuple star system, one of only two known star systems with a multiplicity of 7, the other being Nu Scorpii.
TZ Cassiopeiae(TZ Cas, HIP 117763, SAO 20912) is a variable star in the constellation Cassiopeia with an apparent magnitude of around +9 to +10. It is approximately 8,400 light-years away from Earth. The star is a red supergiant star with a spectral type of M3 and a temperature around 3,600 K.
Nova Cassiopeiae 2021, also known V1405 Cassiopeiae, was a nova in the constellation Cassiopeia. It reached a peak brightness of magnitude 5.449 on May 9, 2021, making it visible to the naked eye. It was discovered by Japanese amateur astronomer Yuji Nakamura of Kameyama, Japan, at 10:10 UT on March 18, 2021. The nova was first seen by Nakamura in four 15 second CCD exposures with a 135mm F/4 lens, when it was at magnitude 9.3. Nothing was seen brighter than magnitude 13.0 with the same equipment in exposures taken at 10:12 UT on March 14, 2021. For the first seven months after discovery, the nova's brightness stayed at a rough plateau, fading and rebrightening at least eight times; it is considered a very slow nova. After the seven month long series of peaks, Nova Cassiopeiae began a linear decline in brightness. This nova has been detected throughout the electromagnetic spectrum, from radio to gamma rays.
12 Cassiopeiae is a white giant in the constellation Cassiopeia, about 860 light years away. It has an apparent magnitude of 5.4, so it faintly visible to the naked eye.
