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Common exoplanet 17 EP

HD 217958 b

RA 346.1366° · Dec -25.6918° · exoplanet

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Score breakdown

· 3 badges
17 pts · Common
Common 22 pts → Uncommon
  • Orbits a Sun-like star +8
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 17

5 more points to reach Uncommon.

Badges

  • Confirmed exoplanet · +5
  • Gas giant · +4
  • 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.

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 8.1 it is just past naked-eye reach — ordinary binoculars will pull it in.
  • 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. ≈ 3.5 million years at Voyager 1's speed (17 km/s).

Properties

density gcc
0.32
diameter km
181138.04
discovery facility
Multiple Observatories
discovery method
Radial Velocity
discovery year
2022
dist ly
201.5504
eccentricity
0.156
eq temp k
169.89
host star teff
5930.64
inclination
91.357
insolation
0.1388
mag
8.05
mass earth
166.5421
name
HD 217958 b
orbital period days
2560.1977
radius earth
14.2
semi major au
3.758
sys num planets
1
sys num stars
1

Nearby objects

About HD 217958 b

HD 217958 b is a common exoplanet. It lies about 201.6 light-years from Earth, shines at apparent magnitude 8.05, has an equilibrium temperature near 170 K and spans roughly 14.2 Earth radii.

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 8.05, it is an easy target for binoculars.

Like any astronomical target, HD 217958 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 217958 b is a common exoplanet

HD 217958 b scores 17 points on Spacedle's rarity scale, which places it in the common tier. Another 5 points would lift it into a rarer tier.

That score comes from 3 science badges — Confirmed exoplanet, Gas giant 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.