← Back to dex
Uncommon star 30 EP

121 Tau

RA 83.8630° · Dec 24.0396° · star

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

Computing the sky for your location…

Score breakdown

· 6 badges
30 pts · Uncommon
Uncommon 34 pts → Rare
  • Naked-eye visible +8
  • Hot blue B-type star +6
  • Subgiant (leaving the main sequence) +5
  • Blue-white star +5
  • Star +3
  • On the zodiac +3
Total score 30

4 more points to reach Rare.

Badges

  • Star · +3
  • Naked-eye visible · +8
  • On the zodiac · +3
  • Hot blue B-type star · +6
  • Subgiant (leaving the main sequence) · +5
  • Blue-white star · +5

Trivia

What it actually is

  • Spectral class. Its spectrum reads B2.5IV — 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 subgiant, caught in the act of leaving the main sequence as the hydrogen in its core runs out.

Sense of scale

  • In perspective. Far away by human standards, yet still a local address inside the Milky Way's spiral arms.

Find it in the sky

  • How to spot it. At magnitude 5.4 you can see it with your own eyes from a dark site, over in Taurus.
  • 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 December — that's when to go looking.

Could we get there?

  • Verdict. Hopelessly far for any craft humanity can build today.

Getting there

  • Aboard Voyager 1. ≈ 9.7 million years at Voyager 1's speed (17 km/s).

Properties

absmag
-0.776
bv
-0.092
constellation
Tau
dist ly
552.8067
luminosity
177.9918
mag
5.37
name
121 Tau
spect
B2.5IV

About 121 Tau

121 Tau is an uncommon star. It lies about 552.8 light-years from Earth, sits in the constellation Tau, shines at apparent magnitude 5.37 and has spectral type B2.5IV.

Its spectrum reads B2.5IV — 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 121 Tau in the constellation Tau. At apparent magnitude 5.37, it can be glimpsed with the unaided eye under dark skies.

Like any astronomical target, 121 Tau 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 121 Tau is an uncommon star

121 Tau scores 30 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 4 points would lift it into a rarer tier.

That score comes from 6 science badges — Star, Naked-eye visible, On the zodiac, Hot blue B-type star, Subgiant (leaving the main sequence) 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.