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Uncommon exoplanet 31 EP

HD 1397 b

RA 4.4472° · Dec -66.3589° · exoplanet

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Score breakdown

· 5 badges
31 pts · Uncommon
Uncommon 34 pts → Rare
  • Hot Jupiter +10
  • Orbits a Sun-like star +8
  • Confirmed exoplanet +5
  • Gas giant +4
  • Found by TESS +4
Total score 31

3 more points to reach Rare.

Badges

  • Confirmed exoplanet · +5
  • Gas giant · +4
  • Hot Jupiter · +10
  • Found by TESS · +4
  • 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 7.8 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 September — that's when to go looking.

Could we get there?

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

Properties

density gcc
0.477
diameter km
146701.8362
discovery facility
Transiting Exoplanet Survey Satellite (TESS)
discovery method
Transit
discovery year
2018
dist ly
259.523
eccentricity
0.251
eq temp k
1228.3
host star teff
5521
inclination
88.99
insolation
356
mag
7.79
mass earth
131.8995
name
HD 1397 b
orbital period days
11.5353
radius earth
11.5004
semi major au
0.1097
spect
G5 III/IV
sys num planets
1
sys num stars
1

About HD 1397 b

HD 1397 b is an uncommon exoplanet. It lies about 259.5 light-years from Earth, shines at apparent magnitude 7.79, has spectral type G5 III/IV and has an equilibrium temperature near 1,228 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 7.79, it is an easy target for binoculars.

Like any astronomical target, HD 1397 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 1397 b is an uncommon exoplanet

HD 1397 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 5 science badges — Confirmed exoplanet, Gas giant, Hot Jupiter, Found by TESS 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.