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Epic exoplanet 65 EP

HD 187123 b

RA 296.7429° · Dec 34.4190° · exoplanet

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Score breakdown

· 7 badges
65 pts · Epic
Epic 78 pts → Anomaly
  • Found before the year 2000 +18
  • Lava world +14
  • Tidally locked +10
  • Orbits a Sun-like star +8
  • Multi-planet system +6
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 65

13 more points to reach Anomaly.

Badges

  • Confirmed exoplanet · +5
  • Gas giant · +4
  • Lava world · +14
  • Tidally locked · +10
  • Multi-planet system · +6
  • Orbits a Sun-like star · +8
  • Found before the year 2000 · +18

Trivia

What makes it special

  • Lava world. Its surface is almost certainly an ocean of molten rock, kept liquid by the star it hugs.

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.
  • Crowded system. One of at least 2 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 7.8 it is just past naked-eye reach — ordinary binoculars will pull it in.
  • Northern sky. It rides the northern half of the sky — an easier target the further north you are.

Properties

density gcc
0.319
diameter km
181138.04
discovery facility
W. M. Keck Observatory
discovery method
Radial Velocity
discovery year
1998
dist ly
149.8843
eccentricity
0.0103
eq temp k
1450.9
host star teff
5790
inclination
79
insolation
738.4255
mag
7.83
mass earth
166.218
name
HD 187123 b
orbital period days
3.0966
radius earth
14.2
semi major au
0.0426
spect
G3 V
sys num planets
2
sys num stars
1
tidally locked
yes
tidally locked inferred
yes

About HD 187123 b

HD 187123 b is an epic exoplanet. It lies about 149.9 light-years from Earth, shines at apparent magnitude 7.83, has spectral type G3 V and has an equilibrium temperature near 1,451 K.

Its surface is almost certainly an ocean of molten rock, kept liquid by the star it hugs.

How to see it

At apparent magnitude 7.83, it is an easy target for binoculars.

Like any astronomical target, HD 187123 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 187123 b is an epic exoplanet

HD 187123 b scores 65 points on Spacedle's rarity scale, which places it in the epic tier. Another 13 points would lift it into a rarer tier.

That score comes from 7 science badges — Confirmed exoplanet, Gas giant, Lava world, Tidally locked, Multi-planet system, Orbits a Sun-like star and Found before the year 2000 — 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.