Star profile
Theta Circinus
Variable starWhat is Theta Circinus
Theta Circini is a hot blue Be-type star, a Gamma Cassiopeiae variable whose brightness oscillates between magnitudes 4.86 and 5.13 over very short cycles of six and a half hours. It shines from more than fifteen hundred light-years away in the southern Compasses, a constellation Lacaille fixed in the eighteenth century right next to the foot of Centaurus. Its true luminosity exceeds two thousand suns, but distance dims it until it barely registers to the unaided eye.
Where it is and when to see it
Theta Circinus lies in the southern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is May, when it culminates around midnight.
- From London it never rises above the horizon.
- From New York it never rises above the horizon.
- From Sydney it never sets and culminates about 61° up.
It can be seen from anywhere south of 27° N.
It ranks no. 6 in brightness among the 21 stars of Circinus in our catalogue. To find it, start from Alpha Circinus, the brightest: it lies about 3° away (a fist at arm's length covers about 10°).
The light you see today left it about 1,500 years ago.
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Astronomical data for Theta Circinus
- Constellation
- Circinus
- Apparent magnitude
- 5.08
- Distance
- 1510.2 light years
- Coordinates (J2000)
- RA 224.183° · Dec -62.781°
- Catalogue
- HIP 73129 · HD 131492
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Other stars in Circinus
Circinus has 21 stars in Stelvia's catalogue. Here are a few of them.
- Alpha Circinus3.18
- Beta Circinus4.07
- Gamma Circinus4.48
- Epsilon Circinus4.85
- Delta Circinus5.04
- Eta Circinus5.16
- HIP 730365.18
- HIP 721315.36