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Common star 19 EP

HD 42638

RA 92.9691° · Dec 0.7507° · star

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Score breakdown

· 4 badges
19 pts · Common
Common 22 pts → Uncommon
  • In Orion's hunting ground +6
  • White A-type star +5
  • Blue-white star +5
  • Star +3
Total score 19

3 more points to reach Uncommon.

Badges

  • Star · +3
  • In Orion's hunting ground · +6
  • White A-type star · +5
  • Blue-white star · +5

Trivia

Hard to believe

  • True brightness. It pours out about 4.1 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 A0 — 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.

Find it in the sky

  • How to spot it. At magnitude 8.3 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Orion.
  • 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 December — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out blue-white (B−V -0) — the hallmark of a surface far hotter than the Sun's.
  • 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.

By the numbers

  • Surface temperature. Its colour puts the surface at roughly 10410 K, against the Sun's 5778 K.

Properties

absmag
-11.71
bv
-0.022
constellation
Ori
luminosity
4207266.2838
mag
8.29
name
HD 42638
spect
A0

Nearby objects

About HD 42638

HD 42638 is a common star. It sits in the constellation Ori, shines at apparent magnitude 8.29 and has spectral type A0.

Its spectrum reads A0 — 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 42638 in the constellation Ori. At apparent magnitude 8.29, it is an easy target for binoculars.

Like any astronomical target, HD 42638 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 42638 is a common star

HD 42638 scores 19 points on Spacedle's rarity scale, which places it in the common tier. Another 3 points would lift it into a rarer tier.

That score comes from 4 science badges — Star, In Orion's hunting ground, White A-type star and Blue-white 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.