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Uncommon variable star 33 EP

HR 2517

RA 102.2652° · Dec 1.0021° · star

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Score breakdown

· 6 badges
33 pts · Uncommon
Uncommon 34 pts → Rare
  • Bright giant +12
  • Hot blue B-type star +6
  • Variable star +5
  • Blue-white star +5
  • A named variable star +3
  • Barely variable (under 0.05 mag) +2
Total score 33

1 more point to reach Rare.

Badges

  • Variable star · +5
  • Hot blue B-type star · +6
  • Bright giant · +12
  • Blue-white star · +5
  • Barely variable (under 0.05 mag) · +2
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads B3II-III — a blue-white B-type star, with a surface tens of thousands of degrees hot and a life measured in tens of millions of years.
  • Where it is in life. It is a bright giant, well on its way to the largest stars there are.
  • 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 6.2 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Monoceros.
  • 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 January — 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 -0.1) — 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.

Properties

absmag
-13.84
bv
-0.134
constellation
Mon
luminosity
29922646.3661
mag
6.16
name
HR 2517
spect
B3II-III
var amplitude
0.03
var designation
V715
var max
6.142
var min
6.172

Nearby objects

About HR 2517

HR 2517 is an uncommon variable star. It sits in the constellation Mon, shines at apparent magnitude 6.16 and has spectral type B3II-III.

Its spectrum reads B3II-III — a blue-white B-type star, with a surface tens of thousands of degrees hot and a life measured in tens of millions of years.

How to see it

Look for HR 2517 in the constellation Mon. At apparent magnitude 6.16, it is an easy target for binoculars.

Like any astronomical target, HR 2517 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 HR 2517 is an uncommon variable star

HR 2517 scores 33 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 1 point would lift it into a rarer tier.

That score comes from 6 science badges — Variable star, Hot blue B-type star, Bright giant, Blue-white 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.