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Rare exoplanet 39 EP

HD 137388 b

RA 233.9151° · Dec -80.2044° · exoplanet

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Score breakdown

· 3 badges
39 pts · Rare
Rare 50 pts → Epic
  • In the habitable zone +30
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 39

11 more points to reach Epic.

Badges

  • Confirmed exoplanet · +5
  • In the habitable zone · +30
  • Gas giant · +4

Trivia

What makes it special

  • Goldilocks zone. Sits where it's neither too hot nor too cold — liquid water could exist on a surface here.

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

  • 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.
  • What the zone means. The habitable zone is only about temperature: it is the band where liquid water could survive on a surface. It is a promising address, not evidence of anything living.

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 8.7 it is just past naked-eye reach — ordinary binoculars will pull it in.
  • Southern sky only. So far south it never rises for most of the northern hemisphere. To see it you'd have to travel to Chile, South Africa or Australia.
  • Best time of year. It stands highest in the middle of the night around May — that's when to go looking.

Properties

density gcc
0.431
diameter km
118887.784
discovery facility
La Silla Observatory
discovery method
Radial Velocity
discovery year
2011
dist ly
132.0413
eccentricity
0.36
eq temp k
248.42
habitable zone
yes
host star teff
5181
insolation
0.5807
mag
8.71
mass earth
63.566
name
HD 137388 b
orbital period days
330
radius earth
9.32
semi major au
0.89
spect
K2 IV
sys num planets
1
sys num stars
1

Nearby objects

About HD 137388 b

HD 137388 b is a rare exoplanet. It lies about 132 light-years from Earth, shines at apparent magnitude 8.71, has spectral type K2 IV and has an equilibrium temperature near 248 K.

Sits where it's neither too hot nor too cold — liquid water could exist on a surface here.

How to see it

At apparent magnitude 8.71, it is an easy target for binoculars.

Like any astronomical target, HD 137388 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 137388 b is a rare exoplanet

HD 137388 b scores 39 points on Spacedle's rarity scale, which places it in the rare tier. Another 11 points would lift it into a rarer tier.

That score comes from 3 science badges — Confirmed exoplanet, In the habitable zone and Gas giant — 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.