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Uncommon exoplanet 28 EP

HD 39855 b

RA 88.6261° · Dec -19.7044° · exoplanet

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Score breakdown

· 4 badges
28 pts · Uncommon
Uncommon 34 pts → Rare
  • Tidally locked +10
  • Orbits a Sun-like star +8
  • Confirmed exoplanet +5
  • Sub-Neptune +5
Total score 28

6 more points to reach Rare.

Badges

  • Confirmed exoplanet · +5
  • Sub-Neptune · +5
  • Tidally locked · +10
  • Orbits a Sun-like star · +8

Trivia

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. 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. Inside our stellar backyard: every radio broadcast humanity has ever made has already swept past it.

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 December — 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. ≈ 1.3 million years at Voyager 1's speed (17 km/s).

Properties

density gcc
2.02
diameter km
36355.17
discovery facility
Las Campanas Observatory
discovery method
Radial Velocity
discovery year
2019
dist ly
75.8636
eccentricity
0.14
eq temp k
1145.89
host star teff
5576
insolation
287.2
mag
7.51
mass earth
8.5
name
HD 39855 b
orbital period days
3.2498
radius earth
2.85
semi major au
0.041
spect
G8 V
sys num planets
1
sys num stars
1
tidally locked
yes
tidally locked inferred
yes

About HD 39855 b

HD 39855 b is an uncommon exoplanet. It lies about 75.9 light-years from Earth, shines at apparent magnitude 7.51, has spectral type G8 V and has an equilibrium temperature near 1,146 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 7.51, it is an easy target for binoculars.

Like any astronomical target, HD 39855 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 39855 b is an uncommon exoplanet

HD 39855 b scores 28 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 6 points would lift it into a rarer tier.

That score comes from 4 science badges — Confirmed exoplanet, Sub-Neptune, Tidally locked 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.