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Common exoplanet 21 EP

81 Cet b

RA 39.4244° · Dec -3.3964° · exoplanet

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Score breakdown

· 3 badges
21 pts · Common
Common 22 pts → Uncommon
  • Its star is visible to the naked eye +12
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 21

1 more point to reach Uncommon.

Badges

  • Confirmed exoplanet · +5
  • Gas giant · +4
  • Its star is visible to the naked eye · +12

Trivia

What it actually is

  • What it is made of. Too light to be solid rock and too heavy to be all gas: most likely a deep global ocean or a thick steamy envelope over a rocky core.

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 5.6 you can see it with your own eyes from a dark site.
  • Seen from everywhere. It sits almost on the celestial equator, so it can be seen from essentially anywhere on Earth.
  • Best time of year. It stands highest in the middle of the night around October — 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. ≈ 5.8 million years at Voyager 1's speed (17 km/s).
  • Fastest probe ever. ≈ 515.7 thousand years even at the Parker Solar Probe's 192 km/s.

Properties

density gcc
2.57
diameter km
167106.22
discovery facility
Okayama Astrophysical Observatory
discovery method
Radial Velocity
discovery year
2008
dist ly
330.2656
eccentricity
0.037
eq temp k
526.92
host star teff
4734
insolation
13.0071
mag
5.6431
mass earth
1051.0585
name
81 Cet b
orbital period days
1005.57
radius earth
13.1
semi major au
2.104
spect
G5 III
sys num planets
1
sys num stars
1

About 81 Cet b

81 Cet b is a common exoplanet. It lies about 330.3 light-years from Earth, shines at apparent magnitude 5.64, has spectral type G5 III and has an equilibrium temperature near 527 K.

Too light to be solid rock and too heavy to be all gas: most likely a deep global ocean or a thick steamy envelope over a rocky core.

How to see it

At apparent magnitude 5.64, it can be glimpsed with the unaided eye under dark skies.

Like any astronomical target, 81 Cet 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 81 Cet b is a common exoplanet

81 Cet b scores 21 points on Spacedle's rarity scale, which places it in the common tier. Another 1 point would lift it into a rarer tier.

That score comes from 3 science badges — Confirmed exoplanet, Gas giant and Its star is visible to the naked eye — 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.