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Haedus II, Hoedus II, Eta Aurigae, 10 Aurigae

Proper NamesHaedus, Haedus II, Hoedus II
Bayer DesignationEta Aurigae
Flamsteed Number10 Aurigae
HR (BSC)1641
Right Ascension5h 6m 31s
Declination+41° 14' 4"
Distance243 light years
75 parsecs
MagnitudeApparent: +3.17
Absolute: -1.19
Spectral ClassB3V blue main sequence star
Optimum VisibilityDecember
NotesHaedus is a main sequence star, but a notably large and massive example: it has a mass some five times that of the Sun, and extends to approximately four times the Sun's diameter. A rapidly-rotating star, Haedus has no other known companion stars or planetary bodies in its system.
Image of Hoedus II

The processes that drive blue Haedus are not yet fully documented, but there is some evidence that its brightness may shift very slightly over a 24-day period. This hypothetical illustration shows the volatile star casting off a 'shell' of plasma; one among many possible causes for its apparent variability.

A variable blue star in the constellation of Auriga, the Charioteer. This star is also known as Haedus II or Hoedus II, but its only connection with Haedus I (also called Saclateni) is that they appear to lie close together in the sky - in fact, they are about five hundred light years apart and are quite unrelated to one another.

The orange star to the west of Haedus is Zeta Aurigae, now formally known as Saclateni, but the two stars were traditionally given the names Haedus I (for orange Zeta Aurigae) and Haedus II (for blue Eta Aurigae, which in fact lies much closer to the Sun than its orange 'companion' in Earth's sky). Imagery provided by Aladin sky atlas


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