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Rare exoplanet 39 EP

K2-129 b

RA 289.1485° · Dec -25.6463° · exoplanet

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Score breakdown

· 4 badges
39 pts · Rare
Rare 50 pts → Epic
  • Earth-sized +16
  • Tidally locked +10
  • Orbits a red dwarf +8
  • Confirmed exoplanet +5
Total score 39

11 more points to reach Epic.

Badges

  • Confirmed exoplanet · +5
  • Earth-sized · +16
  • Tidally locked · +10
  • Orbits a red dwarf · +8

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. Its density says rock, though lighter than Earth's mix: probably less iron, or a thick shell of water and ice over the top.

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 13.6 it is far too faint for the eye: this one belongs to cameras and long exposures.
  • 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 July — that's when to go looking.

Could we get there?

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

Properties

density gcc
5.47
diameter km
13266.448
discovery facility
K2
discovery method
Transit
discovery year
2017
dist ly
90.6573
eccentricity
0.13
eq temp k
419.19
host star teff
3459.09
inclination
89.21
insolation
4.5
mag
13.639
mass earth
1.12
name
K2-129 b
orbital period days
8.2395
radius earth
1.04
semi major au
0.057
sys num planets
1
sys num stars
1
tidally locked
yes
tidally locked inferred
yes

About K2-129 b

K2-129 b is a rare exoplanet. It lies about 90.7 light-years from Earth, shines at apparent magnitude 13.64, has an equilibrium temperature near 419 K and spans roughly 1.04 Earth radii.

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 13.64, it takes a larger telescope or a long-exposure image to capture.

Like any astronomical target, K2-129 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 K2-129 b is a rare exoplanet

K2-129 b scores 39 points on Spacedle's rarity scale, which places it in the rare tier. Another 11 points would lift it into a rarer tier.

That score comes from 4 science badges — Confirmed exoplanet, Earth-sized, Tidally locked and Orbits a red dwarf — 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.