About HD 216105
HD 216105 is a common variable star. It sits in the constellation Lac, shines at apparent magnitude 8.41 and has spectral type F7.5.
Its spectrum reads F7.5 — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
Common variable star 15 EP
HD 216105
RA 342.2633° · Dec 56.4282° · star
Score breakdown
· 4 badgesCommon 22 pts → Uncommon
- Variable star +5
- Gently variable +4
- Yellow-white F-type star +3
- A named variable star +3
Total score 15
7 more points to reach Uncommon.
Badges
- Variable star · +5
- Yellow-white F-type star · +3
- Gently variable · +4
- A named variable star · +3
Trivia
Hard to believe
- True brightness. It pours out about 3.7 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 F7.5 — 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 8.4 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Lacerta.
- Northern sky. It rides the northern half of the sky — an easier target the further north you are.
- Best time of year. It stands highest in the middle of the night around September — that's when to go looking.
Its true colour
- Its true colour. Measured through blue and visual filters it comes out orange (B−V 0.8) — 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
- -11.59
- bv
- 0.821
- constellation
- Lac
- luminosity
- 3767037.9898
- mag
- 8.41
- name
- HD 216105
- spect
- F7.5
- var amplitude
- 0.42
- var designation
- X
- var max
- 8.263
- var min
- 8.683
Nearby objects
How to see it
Look for HD 216105 in the constellation Lac. At apparent magnitude 8.41, it is an easy target for binoculars.
Like any astronomical target, HD 216105 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 216105 is a common variable star
HD 216105 scores 15 points on Spacedle's rarity scale, which places it in the common tier. Another 7 points would lift it into a rarer tier.
That score comes from 4 science badges — Variable star, Yellow-white F-type star, Gently 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.