← Back to dex
Rare exoplanet 46 EP

HD 191939 b

RA 302.0256° · Dec 66.8503° · exoplanet

Loading sky survey…
🌌 View in 3D star map
Tonight’s visibility

Computing the sky for your location…

Score breakdown

· 6 badges
46 pts · Rare
Rare 50 pts → Epic
  • Richly packed system +14
  • Tidally locked +10
  • Orbits a Sun-like star +8
  • Confirmed exoplanet +5
  • Sub-Neptune +5
  • Found by TESS +4
Total score 46

4 more points to reach Epic.

Badges

  • Confirmed exoplanet · +5
  • Sub-Neptune · +5
  • Tidally locked · +10
  • Richly packed system · +14
  • 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.
  • What it is made of. Lighter than Neptune — a puffed-up ball of hydrogen and helium with no surface anywhere on it to stand on.
  • Crowded system. One of at least 6 planets orbiting its star.

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 it is just past naked-eye reach — ordinary binoculars will pull it in.
  • Never sets. So far north that from Britain, Canada or northern Europe it never dips below the horizon — it is up every clear night of the year.
  • 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
1.4
diameter km
43498.642
discovery facility
Transiting Exoplanet Survey Satellite (TESS)
discovery method
Transit
discovery year
2020
dist ly
174.8486
eccentricity
0.031
eq temp k
880
host star teff
5348
inclination
88.1
insolation
100
mag
8.97
mass earth
10
name
HD 191939 b
orbital period days
8.8803
radius earth
3.41
semi major au
0.0804
spect
G9 V
sys num planets
6
sys num stars
1
tidally locked
yes
tidally locked inferred
yes

About HD 191939 b

HD 191939 b is a rare exoplanet. It lies about 174.8 light-years from Earth, shines at apparent magnitude 8.97, has spectral type G9 V and has an equilibrium temperature near 880 K.

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 8.97, it is an easy target for binoculars.

Like any astronomical target, HD 191939 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 HD 191939 b is a rare exoplanet

HD 191939 b scores 46 points on Spacedle's rarity scale, which places it in the rare tier. Another 4 points would lift it into a rarer tier.

That score comes from 6 science badges — Confirmed exoplanet, Sub-Neptune, Tidally locked, Richly packed system, 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.