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Uncommon exoplanet 27 EP

K2-391 b

RA 356.2260° · Dec -7.7015° · exoplanet

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Score breakdown

· 4 badges
27 pts · Uncommon
Uncommon 34 pts → Rare
  • Super-Earth +8
  • Orbits a Sun-like star +8
  • Distant (over 1,000 light-years) +6
  • Confirmed exoplanet +5
Total score 27

7 more points to reach Rare.

Badges

  • Confirmed exoplanet · +5
  • Distant (over 1,000 light-years) · +6
  • Super-Earth · +8
  • Orbits a Sun-like star · +8

Trivia

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

Could we get there?

  • Verdict. Impossible with our current technology — and the next millennium of it.

Getting there

  • Aboard Voyager 1. ≈ 29.1 million years at Voyager 1's speed (17 km/s).

Properties

density gcc
5.22
diameter km
17488.7502
discovery facility
K2
discovery method
Transit
discovery year
2022
dist ly
1656.6768
host star teff
5543
mag
12.527
mass earth
2.45
name
K2-391 b
orbital period days
4.6227
radius earth
1.371
spect
G7
sys num planets
1
sys num stars
1

About K2-391 b

K2-391 b is an uncommon exoplanet. It lies about 1,656.7 light-years from Earth, shines at apparent magnitude 12.53, has spectral type G7 and spans roughly 1.37 Earth radii.

It orbits closer to its star than Mercury does to the Sun, completing a lap in less time than Mercury takes.

How to see it

At apparent magnitude 12.53, it takes a larger telescope or a long-exposure image to capture.

Like any astronomical target, K2-391 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 K2-391 b is an uncommon exoplanet

K2-391 b scores 27 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 7 points would lift it into a rarer tier.

That score comes from 4 science badges — Confirmed exoplanet, Distant (over 1,000 light-years), Super-Earth and Orbits a Sun-like 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.