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Common exoplanet 17 EP

HD 102117 b

RA 176.2097° · Dec -58.7040° · 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

  • 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.

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 7.5 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 March — that's when to go looking.

Could we get there?

  • Verdict. Hopelessly far for any craft humanity can build today.

Properties

density gcc
0.489
diameter km
108045.014
discovery facility
La Silla Observatory
discovery method
Radial Velocity
discovery year
2005
dist ly
129.0899
eccentricity
0.12
eq temp k
780.86
host star teff
5655
insolation
63.8539
mag
7.47
mass earth
54.0311
name
HD 102117 b
orbital period days
20.8133
radius earth
8.47
semi major au
0.15
spect
G6 V
sys num planets
1
sys num stars
1

Nearby objects

About HD 102117 b

HD 102117 b is a common exoplanet. It lies about 129.1 light-years from Earth, shines at apparent magnitude 7.47, has spectral type G6 V and has an equilibrium temperature near 781 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 7.47, it is an easy target for binoculars.

Like any astronomical target, HD 102117 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 102117 b is a common exoplanet

HD 102117 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.