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Rare exoplanet 43 EP

HD 191939 e

RA 302.0256° · Dec 66.8503° · exoplanet

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Score breakdown

· 5 badges
43 pts · Rare
Rare 50 pts → Epic
  • Richly packed system +14
  • Puffy low-density world +12
  • Orbits a Sun-like star +8
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 43

7 more points to reach Epic.

Badges

  • Confirmed exoplanet · +5
  • Gas giant · +4
  • Puffy low-density world · +12
  • Richly packed system · +14
  • Orbits a Sun-like star · +8

Trivia

Hard to believe

  • It would float. It is less dense than water. Drop it in a big enough ocean and the whole world would bob on the surface.

What it actually is

  • 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
0.281
diameter km
165830.6
discovery facility
W. M. Keck Observatory
discovery method
Radial Velocity
discovery year
2022
dist ly
174.8486
eccentricity
0.031
eq temp k
390
host star teff
5348
inclination
88.7
insolation
3.9
mag
8.97
mass earth
112.2
name
HD 191939 e
orbital period days
101.12
radius earth
13
semi major au
0.407
spect
G9 V
sys num planets
6
sys num stars
1

Nearby objects

About HD 191939 e

HD 191939 e 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 390 K.

Lighter than Neptune — a puffed-up ball of hydrogen and helium with no surface anywhere on it to stand on.

How to see it

At apparent magnitude 8.97, it is an easy target for binoculars.

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

HD 191939 e scores 43 points on Spacedle's rarity scale, which places it in the rare tier. Another 7 points would lift it into a rarer tier.

That score comes from 5 science badges — Confirmed exoplanet, Gas giant, Puffy low-density world, Richly packed system 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.