Star profile
Kappa 2 Boötis
Variable starWhat is Kappa 2 Boötis
Kappa-2 Boötis carries the traditional name Asellus Tertius —«the third donkey colt»— and pairs with Kappa-1 as a double visible in a small telescope, separated by 13.5 arcseconds. It is an A8 subgiant pulsing as a Delta Scuti variable: its brightness flickers gently every 1.08 hours as it nears the end of its main-sequence life with a nearly exhausted hydrogen core. At 162 light-years, it beats quietly across the cloak of the Herdsman.
Where it is and when to see it
Kappa 2 Boötis lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is March, when it culminates around midnight.
- From London it never sets and culminates about 90° up.
- From New York it never sets and culminates about 79° up.
- From Sydney it culminates about 4° above the horizon.
It can be seen from anywhere north of 38° S.
It ranks no. 17 in brightness among the 88 stars of Boötes in our catalogue. To find it, start from Arcturus, the brightest: it lies about 33° away (a fist at arm's length covers about 10°).
The light you see today left it about 160 years ago.
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Astronomical data for Kappa 2 Boötis
- Constellation
- Boötes
- Apparent magnitude
- 4.53
- Distance
- 163.4 light years
- Coordinates (J2000)
- RA 213.371° · Dec 51.790°
- Catalogue
- HIP 69483 · HD 124675
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Other stars in Boötes
Boötes has 88 stars in Stelvia's catalogue. Here are a few of them.
- ArcturusAlpha Boötis-0.05
- IzarEpsilon Boötis2.35
- MuphridEta Boötis2.68
- Pi 1 Boötis4.49
- Tau Boötis4.50
- Psi Boötis4.52
- Xi Boötis4.54
- Omicron Boötis4.60