Hyades (astronomy)
Amateur shot of the rain star | |
AladinLite | |
Constellation | bull |
Position equinox : J2000.0 |
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Right ascension | 04 h 27 m |
declination | + 15 ° 52 ′ |
Appearance
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|
Brightness (visual) | 0.5 mag |
Angular expansion | 330 ' |
Number of stars | approx. 350 |
Brightest star | θ² tau , 3.4 mag |
Physical data
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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 .
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
- Taurus SEDS.org (English)
- Three-dimensional map of the Hyades cluster (bottom of the page)
- Ken Coswell: The star cluster closest to Earth is in its death throes , on: ScienceNews of July 24, 2020 (Impending disintegration of the star cluster within 30 million years)
Individual evidence
- ↑ a b SIMBAD query
- ↑ The Hyad names in the detailed lexicon of Greek and Roman mythology , founded by Wilhelm Heinrich Roscher