Alpha Persei Cluster | |
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Observation data (2000.0 epoch) | |
Right ascension | 03h 26m 42.0s [1] |
Declination | +48° 48′ 00″ [1] |
Distance | 570 ly [1] (175 pc [1] ) |
Apparent magnitude (V) | 1.2 |
Apparent dimensions (V) | 6.1° [1] |
Physical characteristics | |
Estimated age | 50–70 Mya [2] [3] |
Other designations | Per OB3, [4] Cr 39, Mel 20, OCl 392.0 [5] |
Associations | |
Constellation | Perseus |
The Alpha Persei Cluster, also known as Melotte 20 or Collinder 39, is an open cluster of stars in the northern constellation of Perseus. To the naked eye, the cluster consists of several blue-hued spectral type B stars. The most luminous member is the ~2nd magnitude yellow supergiant Mirfak, also known as Alpha Persei. Bright members also include Delta, Sigma, 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 ~560 light-years (172 pc ). [6] [7] The distance established via the independent analyses agree, thereby making the cluster an important rung on the cosmic distance ladder. As seen from the Earth, the extinction of the cluster due to interstellar dust is around 0.30. [8]
The cluster is centered to the northeast of Alpha Persei. [8] It has a core radius of 11.4 ± 1.4 ly, a half-mass radius of 18 ly, [8] and a tidal radius of 70.6 ± 8.5 ly, [1] with 517 members being identified within the latter. [8] The cluster shows solid evidence of having undergone mass segregation, with the mean stellar mass decreasing toward the edge. [9] The age of this cluster is about 50–70 million years. [2] [3] Cluster member stars show a near-solar metallicity, meaning the abundance of elements with atomic numbers higher than 2 are similar to those in the Sun. [8] The cluster shows evidence of tidal tails, which are most likely of galactic origin. [10]
The cluster field displays evidence of a much larger, background star stream. This feature is quite a bit older than the cluster, with an estimated age of 5 ± 1 Gyr. The center of the stream lies 290 ly from the cluster and it has an overall thickness of 590 ly along the line of sight. This is most likely the remains of an old, massive cluster that now has a combined mass of ~6000 M☉ . [10]
The following prominent stars are considered members of the cluster with high likelihood:
Designation | Spectral type | Visual magnitude |
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α Per (33 Per) [11] | F5Ib | 1.81 |
δ Per (39 Per) | B5III | 3.01 |
ε Per (45 Per) | B1V | 2.88 |
ψ Per [11] | B5Ve | 4.31 |
HD 21278 [12] [13] | B5V | 4.99 |
31 Per [11] | B5V | 5.05 |
29 Per [11] [13] | B3V | 5.16 |
30 Per [13] | B8V | 5.49 |
34 Per | B3V | 4.67 |
48 Per | B3Ve | 4.03 |
HD 21699 | B8 III | 5.49 |
HD 21071 [13] | B7V | 6.09 |
The Wild Duck Cluster is an open cluster of stars in the constellation Scutum. It was discovered by Gottfried Kirch in 1681. Charles Messier included it in his catalogue of diffuse objects in 1764. Its popular name derives from the brighter stars forming a triangle which could resemble a flying flock of ducks. The cluster is located just to the east of the Scutum Star Cloud midpoint.
The Coma Star Cluster is a nearby open cluster located in the constellation Coma Berenices. The cluster contains about 40 brighter stars with a common proper motion. The brighter stars of the cluster make out a distinctive "V" shape as seen when Coma Berenices is rising. The cluster used to represent the tail of Leo. However, in around 240 BC, Ptolemy III renamed it for the Egyptian queen Berenice's legendary sacrifice of her hair.
α Mensae is the brightest star in the constellation Mensa. At a magnitude of 5.09, it is the dimmest lucida in the sky. Due to its declination, on Earth it is best visible from higher latitudes of the southern hemisphere, yet can also be seen, though low in the sky, from just north of the Equator when near its daily arc's highest point, the culmination.
17 Vulpeculae is a single, blue-white hued star in the northern constellation of Vulpecula. The distance to this star can be estimated from its annual parallax shift of 6.8168±0.1430, which yields a separation of roughly 480 light years. It is moving nearer with a heliocentric radial velocity of −8 km/s, and will make its closest approach in around 6.1 million years at a distance of about 419 ly (128.36 pc). The star is faintly visible to the naked eye with an apparent visual magnitude of 5.08.
S Persei is a red supergiant or hypergiant located near the Double Cluster in Perseus, north of the cluster NGC 869. It is a member of the Perseus OB1 association and one of the largest known stars. If placed in the Solar System, its photosphere would engulf the orbit of Jupiter. It is also a semiregular variable, a star whose variations are less regular than those of Mira variables.
Psi Persei is a single Be star in the northern constellation of Perseus. It has an apparent visual magnitude of about 4.2, so it is visible to the naked eye at night under suitably dark skies. Based on parallax measurements, it is located at a distance of roughly 580 light-years from the Earth.
27 Vulpeculae is a single, blue-white star in the northern constellation of Vulpecula. It is a dim star, visible to the naked eye, with an apparent visual magnitude of 5.59. An annual parallax shift of 10.6692±0.0483 mas provides a distance estimate of about 306 light-years. It is moving closer with a heliocentric radial velocity of −22 km/s, and will make perihelion passage at a distance of around 119 ly (36.56 pc) in 3.75 million years.
34 Persei is a binary star system in the northern constellation of Perseus. It is visible to the naked eye as a faint, blue-white hued point of light with a combined apparent visual magnitude of 4.67. The system is located approximately 540 light years away from the Sun based on parallax, but it is drifting closer with a radial velocity of −3.5 km/s. It is a likely member of the Alpha Persei Cluster.
HD 21278 is a binary star system in the constellation Perseus, located within the 60±7 million year old Alpha Persei Cluster. It has a blue-white hue and is visible to the naked eye with a combined apparent visual magnitude of 4.99. The system is located at a distance of approximately 580 light years from the Sun based on parallax, and it is drifting further away with a radial velocity of +1.20 km/s.
30 Persei is a binary star system in the northern constellation Perseus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.49. Based upon an annual parallax shift of 4.46±0.39 mas, is located roughly 730 light years from the Sun. It is a member of the Perseus OB3 association, which includes the Alpha Persei Cluster.
29 Persei is a single star in the northern constellation of Perseus, located approximately 640 light years away from the Sun based on parallax. It is visible to the naked eye as faint, blue-white hued star with an apparent visual magnitude of 5.16. This object is a member of the Alpha Persei Cluster.
114 Tauri, or o Tauri, is a single, blue-white hued star in the zodiac constellation of Taurus. It is a faint star but visible to the naked eye with an apparent visual magnitude of 4.88. The distance to this star, as determined from its annual parallax shift of 5.22±0.21 mas, is roughly 620 light years. It is moving further from the Sun with a heliocentric radial velocity of 16.5 km/s, having come as close as 240 ly (75 pc) some 9.6 million years ago. It is a member of the Cas-Tau OB association of co-moving stars, and has a peculiar velocity of 8.3 km/s.
7 Persei is a star in the constellation Perseus, located 774 light years away from the Sun. While the star bears the Bayer designation Chi Persei, it is not to be confused with the entire cluster NGC 884, commonly referred to as Chi Persei. It is faintly visible to the naked eye as a dim, yellow-hued star with an apparent visual magnitude of 5.99. This object is moving closer to the Earth with a heliocentric radial velocity of −12.5 km/s.
9 Persei is a single variable star in the northern constellation Perseus, located around 4,300 light years away from the Sun. It has the Bayer designation i Persei; 9 Persei is the Flamsteed designation. This body is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of about 5.2. It is moving closer to the Sun with a heliocentric radial velocity of −15.2 km/s. The star is a member of the Perseus OB1 association of co-moving stars.
57 Persei, or m Persei, is a suspected triple star system in the northern constellation of Perseus. It is at the lower limit of visibility to the naked eye, having a combined apparent visual magnitude of 6.08. The annual parallax shift of 16.4 mas provides a distance measure of 199 light years. 57 Persei is moving closer to the Sun with a radial velocity of about −23 km/s and will make perihelion in around 2.6 million years at a distance of roughly 22 ly (6.6 pc).
42 Persei is a binary star system in the northern constellation of Perseus. It has the Bayer designation n Persei, while 42 Persei is the Flamsteed designation. The system is visible to the naked eye as a dim, white-hued point of light with an apparent visual magnitude of 5.11. It is located around 93 parsecs (302 ly) distant from the Sun, but is drifting closer with a radial velocity of −12.4 km/s.
31 Persei is a single star in the northern constellation of Perseus. It is visible to the naked eye as a dim, blue-white hued point of light with an apparent visual magnitude of 5.05. This star is located around 172 parsecs (560 ly) away from the Sun, and it is drifting closer with a radial velocity of −1.6 km/s. It is likely a member of the Alpha Persei Cluster.
3 Persei is a single, orange-hued star in the northern constellation of Perseus. It is dimly visible to the naked eye under good viewing conditions, having an apparent visual magnitude of 5.70 The star is located around 79 parsecs (257 ly) distant, based upon an annual parallax shift of 12.7 mas.
HD 21071 is a blue-white hued variable star in the northern constellation of Perseus. Also known as V576 Persei, it is a sixth magnitude star that is dimly visible to the naked eye under good viewing conditions, having an apparent visual magnitude of 6.09. The brightness of the star varies with a multiperiodic cycle. The distance to HD 21071, as determined from an annual parallax shift of 6.1 mas, is 535 light years. It is a member of the young Alpha Persei cluster, Melotte 20, and moving is closer to the Earth with a heliocentric radial velocity of −1.5 km/s.
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