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Rare exoplanet 49 EP

WASP-39 b

RA 217.3266° · Dec -3.4445° · exoplanet

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Score breakdown

· 6 badges
49 pts · Rare
Rare 50 pts → Epic
  • Puffy low-density world +12
  • Hot Jupiter +10
  • Tidally locked +10
  • Orbits a Sun-like star +8
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 49

1 more point to reach Epic.

Badges

  • Confirmed exoplanet · +5
  • Gas giant · +4
  • Hot Jupiter · +10
  • Tidally locked · +10
  • Puffy low-density world · +12
  • Orbits a Sun-like star · +8

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 12.1 it is far too faint for the eye: this one belongs to cameras and long exposures.
  • 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 April — that's when to go looking.

Could we get there?

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

Properties

density gcc
0.167
diameter km
182876.8504
discovery facility
SuperWASP
discovery method
Transit
discovery year
2011
dist ly
697.9151
eccentricity
0
eq temp k
1166
host star teff
5485
inclination
87.32
insolation
316.269
mag
12.095
mass earth
89.3102
name
WASP-39 b
orbital period days
4.0553
radius earth
14.3363
semi major au
0.0483
sys num planets
1
sys num stars
1
tidally locked
yes
tidally locked inferred
yes

About WASP-39 b

WASP-39 b is a rare exoplanet. It lies about 697.9 light-years from Earth, shines at apparent magnitude 12.1, has an equilibrium temperature near 1,166 K and spans roughly 14.34 Earth radii.

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 12.1, it takes a larger telescope or a long-exposure image to capture.

Like any astronomical target, WASP-39 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 WASP-39 b is a rare exoplanet

WASP-39 b scores 49 points on Spacedle's rarity scale, which places it in the rare tier. Another 1 point would lift it into a rarer tier.

That score comes from 6 science badges — Confirmed exoplanet, Gas giant, Hot Jupiter, Tidally locked, Puffy low-density world 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.