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Uncommon variable star 31 EP

HIP 72838

RA 223.3249° · Dec 35.8958° · star

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Score breakdown

· 6 badges
31 pts · Uncommon
Uncommon 34 pts → Rare
  • Deep red star +8
  • Red dwarf +6
  • Variable star +5
  • Cool red M-type star +5
  • Gently variable +4
  • A named variable star +3
Total score 31

3 more points to reach Rare.

Badges

  • Variable star · +5
  • Cool red M-type star · +5
  • Deep red star · +8
  • Red dwarf · +6
  • Gently variable · +4
  • A named variable star · +3

Trivia

Hard to believe

  • True brightness. It pours out about 981.7 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 M0 — an M-type red star — and M stars are the silent majority: roughly three of every four stars in the galaxy are one.
  • 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 9.8 you'll want a small backyard telescope, over in Boötes.
  • 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 May — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out deep orange-red (B−V 1.5) — one of the coolest surfaces a star can have while still fusing.

By the numbers

  • Surface temperature. Its colour puts the surface at roughly 3750 K, against the Sun's 5778 K.

Properties

absmag
-10.15
bv
1.528
constellation
Boo
luminosity
1000000
mag
9.85
name
HIP 72838
spect
M0
var amplitude
0.13
var designation
ER
var max
9.786
var min
9.916

About HIP 72838

HIP 72838 is an uncommon variable star. It sits in the constellation Boo, shines at apparent magnitude 9.85 and has spectral type M0.

Its spectrum reads M0 — an M-type red star — and M stars are the silent majority: roughly three of every four stars in the galaxy are one.

How to see it

Look for HIP 72838 in the constellation Boo. At apparent magnitude 9.85, a small backyard telescope will bring it into view.

Like any astronomical target, HIP 72838 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 HIP 72838 is an uncommon variable star

HIP 72838 scores 31 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 3 points would lift it into a rarer tier.

That score comes from 6 science badges — Variable star, Cool red M-type star, Deep red star, Red dwarf, Gently 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.