About HD 170656
HD 170656 is an uncommon variable star. It sits in the constellation Sgr, shines at apparent magnitude 7.67 and has spectral type F0V.
Its spectrum reads F0V — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
Uncommon variable star 26 EP
HD 170656
RA 277.8473° · Dec -18.2626° · star
Score breakdown
· 7 badgesUncommon 34 pts → Rare
- Toward the galactic centre +8
- Variable star +5
- On the zodiac +3
- Yellow-white F-type star +3
- A named variable star +3
- Main-sequence star +2
- Barely variable (under 0.05 mag) +2
Total score 26
8 more points to reach Rare.
Badges
- Variable star · +5
- Toward the galactic centre · +8
- On the zodiac · +3
- Yellow-white F-type star · +3
- Main-sequence star · +2
- Barely variable (under 0.05 mag) · +2
- A named variable star · +3
Trivia
What it actually is
- Spectral class. Its spectrum reads F0V — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
- Where it is in life. It is on the main sequence, quietly fusing hydrogen in its core exactly as the Sun does.
- 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 7.7 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Sagittarius.
- Southern sky. It rides the southern half of the sky — an easier target the further south you are.
- Best time of year. It stands highest in the middle of the night around June — that's when to go looking.
Its true colour
- Its true colour. Measured through blue and visual filters it comes out yellow (B−V 0.6) — almost exactly the Sun's own shade — a stellar twin in colour, if not in size.
- 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
- -12.33
- bv
- 0.614
- constellation
- Sgr
- luminosity
- 7447319.7391
- mag
- 7.67
- name
- HD 170656
- spect
- F0V
- var amplitude
- 0.03
- var designation
- V
- var max
- 7.653
- var min
- 7.683
How to see it
Look for HD 170656 in the constellation Sgr. At apparent magnitude 7.67, it is an easy target for binoculars.
Like any astronomical target, HD 170656 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 170656 is an uncommon variable star
HD 170656 scores 26 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 8 points would lift it into a rarer tier.
That score comes from 7 science badges — Variable star, Toward the galactic centre, On the zodiac, Yellow-white F-type star, Main-sequence star, Barely variable (under 0.05 mag) 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.