Delta Tauri

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The Bayer designation Delta Tauri (δ Tau, δ Tauri) is shared by three star systems in the constellation Taurus. They are all members of the Hyades star cluster.

Because they are close to the ecliptic, these stars can be occulted by the Moon and, very rarely, by planets. The last occultation of δ¹ Tauri by a planet took place on 3 January 1818, when it was occulted by Venus.

δ¹ Tauri[edit]

δ¹ Tauri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Taurus
Right ascension 04h 22m 56.1s
Declination +17° 32' 33"
Apparent magnitude (V) +3.77
Distance 153 ± 7 ly
(47 ± 2 pc)
Spectral type K0-IIICN0.5
Other designations
Hyadum II, 61 Tauri, HR 1373,
HD 27697, BD+17 712,
FK5 162, HIP 20455, SAO 93897,
GC 5304, CCDM 04229+1733

δ¹ Tauri is a triple star approximately 153 light years from Earth and has the traditional name Hyadum II, which is Latin for "Second Hyad", and the name Eudora (Greek Ευδωρη), who was one of the Hyades sisters[citation needed].

The primary component, Delta-1 Tauri A, is an orange K-type giant with an apparent magnitude of +3.77. Delta-1 has a luminosity of 74 times that of the Sun and a radius of 11.6 times solar. Its mass is calculated to be 2.6 solar masses. The surface temperature of this star is 4965 kelvins. Its companion, Delta-1 Tauri B, is a 12th magnitude star separated by 107 arcseconds from the primary. It is most likely not physically related to the main star. However, observations of lunar occultations of this star has revealed a much closer, physically related, star that orbits the main star in an eccentric orbit with an average distance of 1.76 AU. This companion takes about 530 days to orbit the main star.


δ² Tauri[edit]

δ² Tauri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Taurus
Right ascension 04h 24m 05.8s
Declination +17° 26' 38"
Apparent magnitude (V) +4.80
Distance 146 ± 6 ly
(45 ± 2 pc)
Spectral type A7V
Other designations
64 Tauri, HR 1380, HD 27819,
BD+17 714, HIP 20542,
SAO 93907, GC 5328,
CCDM 04240+1726

δ² Tauri is a white A-type main sequence dwarf with an apparent magnitude of +4.80. It is approximately 146 light years from Earth and is separated from δ¹ Tauri by 0.23° on the sky.


δ³ Tauri[edit]

δ³ Tauri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Taurus
Right ascension 04h 25m 29.4s
Declination +17° 55' 41"
Apparent magnitude (V) +4.30
Distance 148 ± 5 ly
(45 ± 2 pc)
Spectral type A2IV
Other designations
Kleeia, 68 Tauri, V776 Tauri,
HR 1389, HD 27962,
BD+17 719, HIP 20648,
SAO 93923, GC 5354,
ADS 3206,
CCDM 04255+1755

δ³ Tauri is a triple star system in the constellation Taurus. It is approximately 148 light years from Earth and is separated from δ¹ Tauri by 0.72° on the sky. This star also has the traditional name Cleeia or Kleeia (Greek Κλεεια), who was one of the Hyades sisters.

The primary component, δ³ Tauri A, is a white A-type subgiant with a mean apparent magnitude of +4.30. It is classified as an Alpha2 Canum Venaticorum type variable star and its brightness varies from magnitude +4.29 to +4.32 with a period of 57.25 days. It has a close, 8th magnitude binary companion, δ³ Tauri B, 1.4 arcseconds, or at least 64 AU, away. At 77 arcseconds away is the third component, the 11th magnitude δ³ Tauri C.

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