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Uncommon star 24 EP

HD 172300

RA 280.2360° · Dec -35.1115° · star

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Score breakdown

· 5 badges
24 pts · Uncommon
Uncommon 34 pts → Rare
  • Toward the galactic centre +8
  • White A-type star +5
  • Subgiant (leaving the main sequence) +5
  • Star +3
  • On the zodiac +3
Total score 24

10 more points to reach Rare.

Badges

  • Star · +3
  • Toward the galactic centre · +8
  • On the zodiac · +3
  • White A-type star · +5
  • Subgiant (leaving the main sequence) · +5

Trivia

Hard to believe

  • True brightness. It pours out about 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 A0IV — an A-type star: white-hot, typically about twice the Sun's mass, and the class most of the sky's famous bright stars belong to.
  • Where it is in life. It is a subgiant, caught in the act of leaving the main sequence as the hydrogen in its core runs out.

Find it in the sky

  • How to spot it. At magnitude 9.1 you'll want a small backyard telescope, 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 July — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out brilliant white (B−V 0.1) — hotter and whiter than the Sun, the colour of Sirius or Vega.
  • 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
-10.94
bv
0.121
constellation
Sgr
luminosity
2070141.3488
mag
9.06
name
HD 172300
spect
A0IV

About HD 172300

HD 172300 is an uncommon star. It sits in the constellation Sgr, shines at apparent magnitude 9.06 and has spectral type A0IV.

Its spectrum reads A0IV — an A-type star: white-hot, typically about twice the Sun's mass, and the class most of the sky's famous bright stars belong to.

How to see it

Look for HD 172300 in the constellation Sgr. At apparent magnitude 9.06, a small backyard telescope will bring it into view.

Like any astronomical target, HD 172300 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 172300 is an uncommon star

HD 172300 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 — Star, Toward the galactic centre, On the zodiac, White A-type star and Subgiant (leaving the main sequence) — 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.