About HD 89991
HD 89991 is a rare variable star. It sits in the constellation Car, shines at apparent magnitude 8.84 and has spectral type F8/G0Ib.
Its spectrum reads F8/G0Ib — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
Rare variable star 39 EP
HD 89991
RA 155.3457° · Dec -61.0741° · star
Score breakdown
· 5 badgesRare 50 pts → Epic
- Supergiant +18
- Strongly variable +10
- Variable star +5
- Yellow-white F-type star +3
- A named variable star +3
Total score 39
11 more points to reach Epic.
Badges
- Variable star · +5
- Yellow-white F-type star · +3
- Supergiant · +18
- Strongly variable · +10
- A named variable star · +3
Trivia
Hard to believe
- True brightness. It pours out about 2.5 million times as much light as the Sun. It only looks ordinary because it is so far away.
What it actually is
- Spectral class. Its spectrum reads F8/G0Ib — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
- It changes. This star does not hold still: its brightness rises and falls on a rhythm of hours, days or years, either pulsing in size or being eclipsed by a companion.
Find it in the sky
- How to spot it. At magnitude 8.8 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Carina.
- Southern sky only. So far south it never rises for most of the northern hemisphere. To see it you'd have to travel to Chile, South Africa or Australia.
- Best time of year. It stands highest in the middle of the night around February — that's when to go looking.
Its true colour
- Its true colour. Measured through blue and visual filters it comes out orange (B−V 0.9) — cooler than the Sun, and the kind of star that burns steadily for tens of billions of years.
- Why no green stars. No star ever looks green: a surface hot enough to peak in green also floods out plenty of red and blue, and your eye blends the mixture back to white.
Properties
- absmag
- -11.16
- bv
- 0.909
- constellation
- Car
- luminosity
- 2535128.6305
- mag
- 8.84
- name
- HD 89991
- spect
- F8/G0Ib
- var amplitude
- 0.65
- var designation
- AQ
- var max
- 8.594
- var min
- 9.244
Nearby objects
How to see it
Look for HD 89991 in the constellation Car. At apparent magnitude 8.84, it is an easy target for binoculars.
Like any astronomical target, HD 89991 is best seen from a dark site away from city lights, and when it is above the horizon depends on your latitude and the time of year. The visibility panel above works out tonight's viewing window for your saved location.
Why HD 89991 is a rare variable star
HD 89991 scores 39 points on Spacedle's rarity scale, which places it in the rare tier. Another 11 points would lift it into a rarer tier.
That score comes from 5 science badges — Variable star, Yellow-white F-type star, Supergiant, Strongly variable and A named variable star — each earned for a real, measurable property of the object. Rarity on Spacedle is never random: the more remarkable an object's astrophysics, the more badges it collects, the higher it scores, and the rarer it ranks.