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Uncommon exoplanet 32 EP

TOI-251 b

RA 353.0621° · Dec -37.2559° · exoplanet

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Score breakdown

· 5 badges
32 pts · Uncommon
Uncommon 34 pts → Rare
  • Tidally locked +10
  • Orbits a Sun-like star +8
  • Confirmed exoplanet +5
  • Sub-Neptune +5
  • Found by TESS +4
Total score 32

2 more points to reach Rare.

Badges

  • Confirmed exoplanet · +5
  • Sub-Neptune · +5
  • Tidally locked · +10
  • Found by TESS · +4
  • 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.

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 9.9 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 September — 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. ≈ 5.7 million years at Voyager 1's speed (17 km/s).
  • Fastest probe ever. ≈ 506.8 thousand years even at the Parker Solar Probe's 192 km/s.

Properties

diameter km
34951.988
discovery facility
Transiting Exoplanet Survey Satellite (TESS)
discovery method
Transit
discovery year
2021
dist ly
324.6002
eccentricity
0
eq temp k
1041.19
host star teff
5875
inclination
87.52
insolation
277.7462
mag
9.887
mass earth
317.83
name
TOI-251 b
orbital period days
4.9378
radius earth
2.74
semi major au
0.0574
sys num planets
1
sys num stars
1
tidally locked
yes
tidally locked inferred
yes

About TOI-251 b

TOI-251 b is an uncommon exoplanet. It lies about 324.6 light-years from Earth, shines at apparent magnitude 9.89, has an equilibrium temperature near 1,041 K and spans roughly 2.74 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 9.89, a small backyard telescope will bring it into view.

Like any astronomical target, TOI-251 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 TOI-251 b is an uncommon exoplanet

TOI-251 b scores 32 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 2 points would lift it into a rarer tier.

That score comes from 5 science badges — Confirmed exoplanet, Sub-Neptune, Tidally locked, Found by TESS 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.