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Rare exoplanet 49 EP

HD 154391 b

RA 255.3201° · Dec 60.6489° · exoplanet

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Score breakdown

· 4 badges
49 pts · Rare
Rare 50 pts → Epic
  • In the habitable zone +30
  • Long-period world +10
  • Confirmed exoplanet +5
  • Gas giant +4
Total score 49

1 more point to reach Epic.

Badges

  • Confirmed exoplanet · +5
  • In the habitable zone · +30
  • Gas giant · +4
  • Long-period world · +10

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

  • 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.
  • 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 6.2 it is just past naked-eye reach — ordinary binoculars will pull it in.
  • 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 June — that's when to go looking.

Properties

density gcc
8.14
diameter km
159452.5
discovery facility
Multiple Observatories
discovery method
Radial Velocity
discovery year
2023
dist ly
329.2447
eccentricity
0.2
eq temp k
253.57
habitable zone
yes
host star teff
4909
inclination
47
insolation
0.685
mag
6.1552
mass earth
2892.2385
name
HD 154391 b
orbital period days
5163
radius earth
12.5
semi major au
7.46
spect
K1 III
sys num planets
1
sys num stars
1

Nearby objects

About HD 154391 b

HD 154391 b is a rare exoplanet. It lies about 329.2 light-years from Earth, shines at apparent magnitude 6.16, has spectral type K1 III and has an equilibrium temperature near 254 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 6.16, it is an easy target for binoculars.

Like any astronomical target, HD 154391 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 154391 b is a rare exoplanet

HD 154391 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 4 science badges — Confirmed exoplanet, In the habitable zone, Gas giant and Long-period 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.