About HD 100971
HD 100971 is an uncommon variable star. It sits in the constellation Dra, shines at apparent magnitude 9.83 and has spectral type F5.
Its spectrum reads F5 — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
Uncommon variable star 25 EP
HD 100971
RA 174.4860° · Dec 67.3297° · star
Score breakdown
· 5 badgesUncommon 34 pts → Rare
- Strongly variable +10
- Variable star +5
- Never sets (northern circumpolar) +4
- Yellow-white F-type star +3
- A named variable star +3
Total score 25
9 more points to reach Rare.
Badges
- Variable star · +5
- Never sets (northern circumpolar) · +4
- Yellow-white F-type star · +3
- Strongly variable · +10
- A named variable star · +3
Trivia
Hard to believe
- True brightness. It pours out about 1 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 F5 — 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 9.8 you'll want a small backyard telescope, over in Draco.
- Never sets. So far north that from Britain, Canada or northern Europe it never dips below the horizon — it is up every clear night of the year.
- Best time of year. It stands highest in the middle of the night around March — that's when to go looking.
Its true colour
- Its true colour. Measured through blue and visual filters it comes out yellow-white (B−V 0.3) — a shade brighter and crisper than our own Sun.
- 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
- -10.17
- bv
- 0.348
- constellation
- Dra
- luminosity
- 1018591.3881
- mag
- 9.83
- name
- HD 100971
- spect
- F5
- var amplitude
- 1
- var designation
- SU
- var max
- 9.126
- var min
- 10.126
How to see it
Look for HD 100971 in the constellation Dra. At apparent magnitude 9.83, a small backyard telescope will bring it into view.
Like any astronomical target, HD 100971 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 100971 is an uncommon variable star
HD 100971 scores 25 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 9 points would lift it into a rarer tier.
That score comes from 5 science badges — Variable star, Never sets (northern circumpolar), Yellow-white F-type star, 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.