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Uncommon exoplanet 31 EP

HD 18438 b

RA 46.5318° · Dec 79.4186° · exoplanet

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Score breakdown

· 4 badges
31 pts · Uncommon
Uncommon 34 pts → Rare
  • Its star is visible to the naked eye +12
  • Hot Jupiter +10
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 31

3 more points to reach Rare.

Badges

  • Confirmed exoplanet · +5
  • Gas giant · +4
  • Hot Jupiter · +10
  • Its star is visible to the naked eye · +12

Trivia

Hard to believe

  • Denser than iron. It is packed tighter than solid iron — whatever it is made of, it is not ordinary rock.

What it actually is

  • What it is made of. Denser than Earth — a solid world of rock and iron, with no meaningful atmosphere to speak of by mass.

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 5.5 you can see it with your own eyes from a dark site.
  • Never sets. So far north that from Britain, Canada or northern Europe it never dips below the horizon — it is up every clear night of the year.
  • Best time of year. It stands highest in the middle of the night around November — 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. ≈ 12.8 million years at Voyager 1's speed (17 km/s).

Properties

density gcc
20.7
diameter km
154350.02
discovery facility
Bohyunsan Optical Astronomical Observatory
discovery method
Radial Velocity
discovery year
2023
dist ly
731.0656
eccentricity
0.1
eq temp k
1208.15
host star teff
3860
insolation
210.6576
mag
5.5047
mass earth
6674.3965
name
HD 18438 b
orbital period days
803
radius earth
12.1
semi major au
2.1
spect
M2.5 III
sys num planets
1
sys num stars
1

About HD 18438 b

HD 18438 b is an uncommon exoplanet. It lies about 731.1 light-years from Earth, shines at apparent magnitude 5.5, has spectral type M2.5 III and has an equilibrium temperature near 1,208 K.

Denser than Earth — a solid world of rock and iron, with no meaningful atmosphere to speak of by mass.

How to see it

At apparent magnitude 5.5, it can be glimpsed with the unaided eye under dark skies.

Like any astronomical target, HD 18438 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 18438 b is an uncommon exoplanet

HD 18438 b scores 31 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 3 points would lift it into a rarer tier.

That score comes from 4 science badges — Confirmed exoplanet, Gas giant, Hot Jupiter 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.