Alpha Persei Cluster
Encyclopedia
The Alpha Persei Cluster, also known as Melotte 20 or Collinder 39, is an open cluster
in the constellation
of Perseus
. To the naked eye, the cluster consists of several blue spectral type B type stars. The most luminous member is the ~2nd magnitude white-yellow supergiant Mirfak, also known as Alpha Persei
. Bright members also include Delta
, Epsilon
, Psi
, 29, 30, 34 and 48 Persei. The Hipparcos
satellite and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster of ~172 pc. The distance established via the independent analyses agree, thereby making the cluster an important rung on the cosmic distance ladder
. The age of this cluster is about 50-70 million years.
Open cluster
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Perseus
Perseus (constellation)
Perseus is a constellation in the northern sky, named after the Greek hero Perseus. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations defined by the International Astronomical Union...
. To the naked eye, the cluster consists of several blue spectral type B type stars. The most luminous member is the ~2nd magnitude white-yellow supergiant Mirfak, also known as Alpha Persei
Alpha Persei
Alpha Persei is the brightest star in the constellation of Perseus, just outshining the constellation's best known star Algol. It also bears the traditional names Mirfak and Algenib...
. Bright members also include Delta
Delta Persei
Delta Persei is a Class B5III, third-magnitude star in the constellation Perseus. Delta Persei is actually a blue giant star that is the second brightest star of the open star cluster known as the Alpha Persei, second only to Mirfak. The Delta Persei stellar system is located about 530 light-years...
, Epsilon
Epsilon Persei
Epsilon Persei is a Class B1V, third-magnitude star in the constellation Perseus. Epsilon Persei is actually a multiple star system consisting of two main components: a blue main-sequence star of class B0.5V and a magnitude of 2.90, and a lesser white companion of class A2V and a magnitude of 3.92...
, Psi
Psi Persei
Psi Persei is a Be star in the constellation Perseus. This is a shell star that has a circumstellar disc of gas surrounding the equator. As a result of this disc, the spectrum of this star shows emission lines and the magnitude varies over a period of about a day...
, 29, 30, 34 and 48 Persei. The Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
satellite and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster of ~172 pc. The distance established via the independent analyses agree, thereby making the cluster an important rung on the cosmic distance ladder
Cosmic distance ladder
The cosmic distance ladder is the succession of methods by which astronomers determine the distances to celestial objects. A real direct distance measurement of an astronomical object is possible only for those objects that are "close enough" to Earth...
. The age of this cluster is about 50-70 million years.
Members
| Designations | Spectral type & Luminosity class |
Comments |
|---|---|---|
| α Per Alpha Persei Alpha Persei is the brightest star in the constellation of Perseus, just outshining the constellation's best known star Algol. It also bears the traditional names Mirfak and Algenib... (33 Per) |
F5Ib | |
| δ Per Delta Persei Delta Persei is a Class B5III, third-magnitude star in the constellation Perseus. Delta Persei is actually a blue giant star that is the second brightest star of the open star cluster known as the Alpha Persei, second only to Mirfak. The Delta Persei stellar system is located about 530 light-years... (39 Per) |
B5III | |
| ε Per Epsilon Persei Epsilon Persei is a Class B1V, third-magnitude star in the constellation Perseus. Epsilon Persei is actually a multiple star system consisting of two main components: a blue main-sequence star of class B0.5V and a magnitude of 2.90, and a lesser white companion of class A2V and a magnitude of 3.92... (45 Per) |
B1V | |
| ψ Per Psi Persei Psi Persei is a Be star in the constellation Perseus. This is a shell star that has a circumstellar disc of gas surrounding the equator. As a result of this disc, the spectrum of this star shows emission lines and the magnitude varies over a period of about a day... |
||
| 29 Per | ||
| 30 Per | ||
| 34 Per | ||
| 48 Per | ||