Star profile
Omicron 1 Orionis
Variable starWhat is Omicron 1 Orionis
Omicron-1 Orionis is a remarkable rarity: a red giant of the unusual S class, an intermediate stage on the road from an ordinary M giant to a true carbon star, where zirconium begins to displace titanium in its atmosphere. A semi-regular variable, it drifts between magnitudes 4.65 and 4.88 every 31 days. At 651 light-years it pulses discreetly, far from the Belt's glitter, on Orion's northwestern shoulder.
Where it is and when to see it
Omicron 1 Orionis lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is December, when it culminates around midnight.
- From London it culminates about 53° above the horizon.
- From New York it culminates about 64° above the horizon.
- From Sydney it culminates about 42° above the horizon.
It can be seen from anywhere north of 76° S.
It ranks no. 36 in brightness among the 128 stars of Orion in our catalogue. To find it, start from Rigel, the brightest: it lies about 23° away (a fist at arm's length covers about 10°).
The light you see today left it about 650 years ago.
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Astronomical data for Omicron 1 Orionis
- Constellation
- Orion
- Apparent magnitude
- 4.71
- Distance
- 651.1 light years
- Coordinates (J2000)
- RA 73.133° · Dec 14.251°
- Catalogue
- HIP 22667 · HD 30959
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Other stars in Orion
Orion has 128 stars in Stelvia's catalogue. Here are a few of them.
- RigelBeta Orionis0.18
- BetelgeuseAlpha Orionis0.45
- BellatrixGamma Orionis1.64
- Pi 1 Orionis4.64
- Chi 2 Orionis4.64
- 11 Orionis4.65
- 31 Orionis4.71
- 22 Orionis4.72