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Epic exoplanet 59 EP

HD 181720 b

RA 290.7212° · Dec -32.9208° · exoplanet

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Score breakdown

· 5 badges
59 pts · Epic
Epic 78 pts → Anomaly
  • In the habitable zone +30
  • Puffy low-density world +12
  • Orbits a Sun-like star +8
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 59

19 more points to reach Anomaly.

Badges

  • Confirmed exoplanet · +5
  • In the habitable zone · +30
  • Gas giant · +4
  • Puffy low-density world · +12
  • Orbits a Sun-like star · +8

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 7.8 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 July — that's when to go looking.

Properties

density gcc
0.255
diameter km
178586.8
discovery facility
La Silla Observatory
discovery method
Radial Velocity
discovery year
2009
dist ly
196.3609
eccentricity
0.26
eq temp k
249.06
habitable zone
yes
host star teff
5736
insolation
0.5671
mag
7.84
mass earth
127.132
name
HD 181720 b
orbital period days
956
radius earth
14
semi major au
1.85
spect
G1 V
sys num planets
1
sys num stars
1

Nearby objects

About HD 181720 b

HD 181720 b is an epic exoplanet. It lies about 196.4 light-years from Earth, shines at apparent magnitude 7.84, has spectral type G1 V and has an equilibrium temperature near 249 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 7.84, it is an easy target for binoculars.

Like any astronomical target, HD 181720 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 181720 b is an epic exoplanet

HD 181720 b scores 59 points on Spacedle's rarity scale, which places it in the epic tier. Another 19 points would lift it into a rarer tier.

That score comes from 5 science badges — Confirmed exoplanet, In the habitable zone, Gas giant, 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.