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Uncommon exoplanet 31 EP

HAT-P-18 b

RA 256.3464° · Dec 33.0123° · exoplanet

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Score breakdown

· 4 badges
31 pts · Uncommon
Uncommon 34 pts → Rare
  • Puffy low-density world +12
  • Tidally locked +10
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 31

3 more points to reach Rare.

Badges

  • Confirmed exoplanet · +5
  • Gas giant · +4
  • Tidally locked · +10
  • Puffy low-density world · +12

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 12.6 it is far too faint for the eye: this one belongs to cameras and long exposures.
  • Northern sky. It rides the northern half of the sky — an easier target the further north you are.
  • Best time of year. It stands highest in the middle of the night around June — that's when to go looking.

Could we get there?

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

Properties

density gcc
0.25
diameter km
142269.8986
discovery facility
HATNet
discovery method
Transit
discovery year
2010
dist ly
526.4158
eccentricity
0.084
eq temp k
852
host star teff
4803
inclination
88.8
insolation
82.2407
mag
12.597
mass earth
62.61
name
HAT-P-18 b
orbital period days
5.508
radius earth
11.153
semi major au
0.0559
spect
K2
sys num planets
1
sys num stars
1
tidally locked
yes
tidally locked inferred
yes

About HAT-P-18 b

HAT-P-18 b is an uncommon exoplanet. It lies about 526.4 light-years from Earth, shines at apparent magnitude 12.6, has spectral type K2 and has an equilibrium temperature near 852 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 12.6, it takes a larger telescope or a long-exposure image to capture.

Like any astronomical target, HAT-P-18 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 HAT-P-18 b is an uncommon exoplanet

HAT-P-18 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, Tidally locked and Puffy low-density world — 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.