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Rare exoplanet 41 EP

HD 21749 c

RA 51.7502° · Dec -63.5002° · exoplanet

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Score breakdown

· 5 badges
41 pts · Rare
Rare 50 pts → Epic
  • Earth-sized +16
  • Tidally locked +10
  • Multi-planet system +6
  • Confirmed exoplanet +5
  • Found by TESS +4
Total score 41

9 more points to reach Epic.

Badges

  • Confirmed exoplanet · +5
  • Earth-sized · +16
  • Tidally locked · +10
  • Multi-planet system · +6
  • Found by TESS · +4

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.

Hard to believe

  • Denser than iron. It is packed tighter than solid iron — whatever it is made of, it is not ordinary rock.

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 2 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 8.1 it is just past naked-eye reach — ordinary binoculars will pull it in.
  • Southern sky only. So far south it never rises for most of the northern hemisphere. To see it you'd have to travel to Chile, South Africa or Australia.

Properties

density gcc
31.93
diameter km
11378.5304
discovery facility
Transiting Exoplanet Survey Satellite (TESS)
discovery method
Transit
discovery year
2019
dist ly
53.2287
eq temp k
701
host star teff
4640
inclination
88.9
insolation
305.9425
mag
8.08
mass earth
3.7
name
HD 21749 c
orbital period days
7.7899
radius earth
0.892
semi major au
0.0695
spect
K4.5
sys num planets
2
sys num stars
1
tidally locked
yes
tidally locked inferred
yes

Nearby objects

About HD 21749 c

HD 21749 c is a rare exoplanet. It lies about 53.2 light-years from Earth, shines at apparent magnitude 8.08, has spectral type K4.5 and has an equilibrium temperature near 701 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 8.08, it is an easy target for binoculars.

Like any astronomical target, HD 21749 c 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 HD 21749 c is a rare exoplanet

HD 21749 c scores 41 points on Spacedle's rarity scale, which places it in the rare tier. Another 9 points would lift it into a rarer tier.

That score comes from 5 science badges — Confirmed exoplanet, Earth-sized, Tidally locked, Multi-planet system and Found by TESS — 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.