Star profile

31 Orionis

Variable star

3D likeness based on its real data · class K · ~4,200 K

What is 31 Orionis

31 Orionis —also catalogued as CI Orionis for its variability— is a K5III orange giant set just north of the Hunter's belt. Astronomers detected slow oscillations hinting at a 141-day cycle, though the General Catalogue still treats it as a whisper awaiting confirmation. With a faint companion ten magnitudes dimmer 12.7 arcseconds away, it offers an intimate contrast: a mature ember beside a distant spark, both suspended in the same view of Orion.

Where it is and when to see it

31 Orionis lies in the southern 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 37° above the horizon.
From New York it culminates about 48° above the horizon.
From Sydney it culminates about 57° above the horizon.

It can be seen from anywhere south of 89° N.

It ranks no. 37 in brightness among the 128 stars of Orion in our catalogue. To find it, start from Rigel, the brightest: it lies about 8° away (a fist at arm's length covers about 10°).

The light you see today left it about 510 years ago.

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Astronomical data for 31 Orionis

Constellation: Orion
Apparent magnitude: 4.71
Distance: 508.1 light years
Coordinates (J2000): RA 82.433° · Dec -1.092°
Catalogue: HIP 25737 · HD 36167

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Other stars in Orion

Orion has 128 stars in Stelvia's catalogue. Here are a few of them.

See all 128 stars in Orion