← Back to dex
Trash star 13 EP

HD 239748

RA 325.9221° · Dec 58.2398° · star

Loading sky survey…
🌌 View in 3D star map
Tonight’s visibility

Computing the sky for your location…

Score breakdown

· 3 badges
13 pts · Trash
Trash 15 pts → Common
  • Hot blue B-type star +6
  • Never sets (northern circumpolar) +4
  • Star +3
Total score 13

2 more points to reach Common.

Badges

  • Star · +3
  • Never sets (northern circumpolar) · +4
  • Hot blue B-type star · +6

Trivia

Hard to believe

  • True brightness. It pours out about 2.7 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 B2 — 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.

Find it in the sky

  • How to spot it. At magnitude 8.8 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Cepheus.
  • 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 August — 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 0.2) — 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.

By the numbers

  • Surface temperature. Its colour puts the surface at roughly 8400 K, against the Sun's 5778 K.

Properties

absmag
-11.25
bv
0.17
constellation
Cep
luminosity
2754228.7033
mag
8.75
name
HD 239748
spect
B2

Nearby objects

About HD 239748

HD 239748 is a trash star. It sits in the constellation Cep, shines at apparent magnitude 8.75 and has spectral type B2.

Its spectrum reads B2 — 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 HD 239748 in the constellation Cep. At apparent magnitude 8.75, it is an easy target for binoculars.

Like any astronomical target, HD 239748 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 239748 is a trash star

HD 239748 scores 13 points on Spacedle's rarity scale, which places it in the trash tier. Another 2 points would lift it into a rarer tier.

That score comes from 3 science badges — Star, Never sets (northern circumpolar) and Hot blue B-type 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.