About HD 250642
HD 250642 is an uncommon variable star. It sits in the constellation Gem, shines at apparent magnitude 9.9 and has spectral type F6.7.
Its spectrum reads F6.7 — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
Uncommon variable star 24 EP
HD 250642
RA 90.6525° · Dec 22.2341° · star
Score breakdown
· 5 badgesUncommon 34 pts → Rare
- Strongly variable +10
- Variable star +5
- On the zodiac +3
- Yellow-white F-type star +3
- A named variable star +3
Total score 24
10 more points to reach Rare.
Badges
- Variable star · +5
- On the zodiac · +3
- Yellow-white F-type star · +3
- Strongly variable · +10
- A named variable star · +3
Trivia
Hard to believe
- True brightness. It pours out about 937.6 thousand 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 F6.7 — 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 9.9 you'll want a small backyard telescope, over in Gemini.
- 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 December — 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
- -10.1
- bv
- 0.94
- constellation
- Gem
- luminosity
- 954992.586
- mag
- 9.9
- name
- HD 250642
- spect
- F6.7
- var amplitude
- 0.96
- var designation
- RZ
- var max
- 9.364
- var min
- 10.324
How to see it
Look for HD 250642 in the constellation Gem. At apparent magnitude 9.9, a small backyard telescope will bring it into view.
Like any astronomical target, HD 250642 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 250642 is an uncommon variable star
HD 250642 scores 24 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 10 points would lift it into a rarer tier.
That score comes from 5 science badges — Variable star, On the zodiac, 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.