About HD 172902
HD 172902 is an uncommon variable star. It sits in the constellation Sct, shines at apparent magnitude 9.59 and has spectral type G1.2.
Its spectrum reads G1.2 — a G-type star: the very same spectral class as our own Sun.
Uncommon variable star 26 EP
HD 172902
RA 280.7387° · Dec -5.8209° · star
Score breakdown
· 4 badgesUncommon 34 pts → Rare
- Strongly variable +10
- Sun-like G-type star +8
- Variable star +5
- A named variable star +3
Total score 26
8 more points to reach Rare.
Badges
- Variable star · +5
- Sun-like G-type star · +8
- Strongly variable · +10
- A named variable star · +3
Trivia
Hard to believe
- True brightness. It pours out about 1.2 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 G1.2 — a G-type star: the very same spectral class as our own 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 9.6 you'll want a small backyard telescope, over in Scutum.
- Seen from everywhere. It sits almost on the celestial equator, so it can be seen from essentially anywhere on Earth.
- Best time of year. It stands highest in the middle of the night around July — that's when to go looking.
Its true colour
- Its true colour. Measured through blue and visual filters it comes out orange (B−V 1.3) — cooler than the Sun, and the kind of star that burns steadily for tens of billions of years.
By the numbers
- Surface temperature. Its colour puts the surface at roughly 4160 K, against the Sun's 5778 K.
Properties
- absmag
- -10.41
- bv
- 1.277
- constellation
- Sct
- luminosity
- 1270574.1052
- mag
- 9.59
- name
- HD 172902
- spect
- G1.2
- var amplitude
- 1
- var designation
- Z
- var max
- 9.001
- var min
- 10.001
Nearby objects
- Trash HIP 91716 star · 0.2° away
- Uncommon J1844-0538 pulsar · 0.3° away
- Uncommon J1842-0612 pulsar · 0.4° away
- Trash NGC 6683 cluster · 0.4° away
- Trash IC 4768 cluster · 0.5° away
- Common HIP 91738 variable star · 0.5° away
- Uncommon J1841-0524 pulsar · 0.5° away
- Rare HIP 91613 variable star · 0.6° away
How to see it
Look for HD 172902 in the constellation Sct. At apparent magnitude 9.59, a small backyard telescope will bring it into view.
Like any astronomical target, HD 172902 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 172902 is an uncommon variable star
HD 172902 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 4 science badges — Variable star, Sun-like G-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.