Hyades (astronomy)

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Open cluster
Hyades
Amateur shot of the rain star
Amateur shot of the rain star
AladinLite
Constellation bull
Position
equinox : J2000.0
Right ascension 04 h 27 m
declination + 15 ° 52 ′
Appearance

Brightness  (visual) 0.5 mag
Angular expansion 330 '
Number of stars approx. 350
Brightest star θ² tau , 3.4 mag
Physical data

distance  153 ly
(47 pc )
diameter 15 years
Age 625 million years
history
Catalog names
 C 0424 + 157 • OCl 456 •  Mel  25 •  Cr  50 •  C 41

The Hyades (Greek hyein , to let rain), also rain stars or Taurus stream , are an open star cluster in the constellation Taurus , the brightest stars of which are visible to the naked eye . They are easy to find as a V-shaped arrangement of the brightest stars of the star cluster directly on the main star of Taurus, Aldebaran . Aldebaran itself, however, does not belong to the Hyades, but is far ahead of it. The star cluster is not listed in the Messier and NGC catalogs, in the Melotte catalog it is listed as Melotte 25, in the Caldwell catalog as C41.

Details

The star cluster is visible in Central Europe from September to April in the northern sky. The core of the Hyades has a diameter of about 4 parsecs , cluster members lying outside can still be found within a radius of up to 24 pc . The distance is approx. 44 pc , the age approx. 600 million years, thus somewhat older than the Pleiades . The overall brightness corresponds to a brightness of about 1 mag . The Hyades, together with the Pleiades, form the so-called Golden Gate of the Ecliptic .

Because of their uniform movement in space, the Hyaden group is also counted among the movement star clusters. It is characterized by the uniform change in position of all stars on a virtual convergence point and comprises around 350 stars that move uniformly at around 43 km / s in this direction. This point, also known as the "vertex", is located east of Betelgeuse in the constellation Orion . Proper motion, age, and composition of the Hyades are similar to those of the Praesepe star cluster, indicating a common origin for both clusters, even though they are hundreds of light years apart today.

Due to their proximity to our solar system, the hyads play an important role in modern astrophysics. Using classic trigonometric methods ( parallax and star current parallax ), the distance and thus the absolute brightness of the individual stars of the star cluster can be precisely determined. Other measurement methods for more distant objects build on this, including outside of our galaxy, including the Cepheids in particular .

  • Star map of the Hyades.

  • The Hyades with the star Aldebaran and the planet Venus in the head of the Taurus of the constellation Taurus (Taurus) at dawn over the eastern horizon with all stars with an apparent brightness up to the fifth magnitude.

Stars

Surname F. apparent
brightness 		Spectral
class 		Mass
( ) 		Proper movement ( mas / a )
right ascension 		Proper movement ( mas / a )
declination 		Distance
(Lj)
Theta2 Tauri (Chamukuy) 78 3.41 A7 III 2.4 + 2.1 103.3 −18.6 157
Epsilon Tauri (Ain) 74 3.53 K0 III 2.7 106.2 −37.8 160
Gamma Tauri (Hyadum I) 54 3.65 K0 III 2.7 115.5 −23.4 144
Delta1 Tauri (Hyadum II) 61 3.76 K0 III 2.54 100.8 −28.1 171
Theta1 Tauri 77 3.84 K0 IIIb 2.9 + 1.3 105.0 −15.1 154
Kappa1 Tauri 65 4.20 A7 IV-V - 105.2 −45.0 152
90 tauri 90 4.27 A6 V - 102.4 −15.8 144
Ypsilon Tauri 69 4.28 A8 Vn - 108.8 −46.8 146
Delta3 Tauri 68 4.30 A2 IV-Vs - 107.6 −34.5 150
71 Tauri 71 4.48 F0 V - 85.4 −14.9 145
Iota Tauri 102 4.62 A7 V - 68.2 −41.3 177
Rho Tauri 86 4.65 A8 V - 103.2 −26.5 144
Sigma2 Tauri 92 4.67 A5 Vn - 83.2 −21.0 160
HD 28527 - 4.80 A6 IV - 104.4 −26.3 148
Delta2 Tauri 64 4.80 A2 Vs - 110.8 −33.2 150

Mythological background

In Greek mythology , the Hyades were daughters of Atlas and Aithra . The information on the number of Hyades varies between five and seven, although the names are not precisely defined. Ambrosia , Eudora , Pedile (probably also Phaesyle or Aesyle), Coronis , Polyxo , Phyto (Phaeo), Thyone (also Dione) are often mentioned . Her only brother, Hyas , was killed while hunting. Their grief and tears aroused the pity of the gods, and so they were placed among the stars as hyads. Even Virgil speaks of the "wet Hyades", and the old Greek name "Rain star" reveals the meaning: The tears flow unchecked on, now fall as rain.

Web links

Commons : Hyaden  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b SIMBAD query
  2. ↑ The Hyad names in the detailed lexicon of Greek and Roman mythology , founded by Wilhelm Heinrich Roscher