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Rare exoplanet 37 EP

GJ 3138 b

RA 32.2977° · Dec -16.3392° · exoplanet

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Score breakdown

· 4 badges
37 pts · Rare
Rare 50 pts → Epic
  • Earth-sized +16
  • Tidally locked +10
  • Multi-planet system +6
  • Confirmed exoplanet +5
Total score 37

13 more points to reach Epic.

Badges

  • Confirmed exoplanet · +5
  • Earth-sized · +16
  • Tidally locked · +10
  • Multi-planet system · +6

Trivia

What makes it special

  • Earth-sized. Genuinely comparable to Earth in size. Worlds in this narrow band are the ones every next-generation telescope is being pointed at.

What it actually is

  • Hugging its star. It orbits closer to its star than Mercury does to the Sun, completing a lap in less time than Mercury takes.
  • What it is made of. Denser than Earth — a solid world of rock and iron, with no meaningful atmosphere to speak of by mass.
  • Crowded system. One of at least 3 planets orbiting its star.

Sense of scale

  • In perspective. Inside our stellar backyard: every radio broadcast humanity has ever made has already swept past it.

Find it in the sky

  • How to spot it. At magnitude 10.8 you'll want a small backyard telescope.
  • Southern sky. It rides the southern half of the sky — an easier target the further south you are.
  • Best time of year. It stands highest in the middle of the night around October — that's when to go looking.

Properties

density gcc
5.95
diameter km
15052.316
discovery facility
La Silla Observatory
discovery method
Radial Velocity
discovery year
2017
dist ly
92.8605
eccentricity
0.19
eq temp k
902.98
host star teff
3717
insolation
118.1
mag
10.8275
mass earth
1.78
name
GJ 3138 b
orbital period days
1.22
radius earth
1.18
semi major au
0.0197
spect
M0
sys num planets
3
sys num stars
1
tidally locked
yes
tidally locked inferred
yes

About GJ 3138 b

GJ 3138 b is a rare exoplanet. It lies about 92.9 light-years from Earth, shines at apparent magnitude 10.83, has spectral type M0 and has an equilibrium temperature near 903 K.

Genuinely comparable to Earth in size. Worlds in this narrow band are the ones every next-generation telescope is being pointed at.

How to see it

At apparent magnitude 10.83, a small backyard telescope will bring it into view.

Like any astronomical target, GJ 3138 b 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 GJ 3138 b is a rare exoplanet

GJ 3138 b scores 37 points on Spacedle's rarity scale, which places it in the rare tier. Another 13 points would lift it into a rarer tier.

That score comes from 4 science badges — Confirmed exoplanet, Earth-sized, Tidally locked and Multi-planet system — 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.