About K2-138 f
K2-138 f is an uncommon exoplanet. It lies about 660.7 light-years from Earth, has an equilibrium temperature near 653 K, spans roughly 2.9 Earth radii and weighs about 1.63 Earth masses.
Crammed into a system of five or more planets.
Uncommon exoplanet 30 EP
K2-138 f
RA 348.9490° · Dec -10.8497° · exoplanet
Score breakdown
· 4 badgesUncommon 33 pts → Rare
- Richly packed system +14
- Multi-planet system +6
- Confirmed exoplanet +5
- Sub-Neptune +5
Total score 30
3 more points to reach Rare.
Badges
- Confirmed exoplanet · +5
- Sub-Neptune · +5
- Multi-planet system · +6
- Richly packed system · +14
Trivia
What makes it special
- Packed system. Crammed into a system of five or more planets.
Could we get there?
- Verdict. Hopelessly far for any craft humanity can build today.
Getting there
- Aboard Voyager 1. ≈ 11.6 million years at Voyager 1's speed (17 km/s).
- Fastest probe ever. ≈ 1 million years even at the Parker Solar Probe's 192 km/s.
- At 10% light speed. ≈ 6607 years in a starship at a tenth of light speed.
- Distance. 661 light-years from Earth.
Look-back time
- Look-back time. The light you'd see left around the year 1365.
Saying hello
- Say hello. A radio message and its reply would take 1321 years round-trip.
Standing on it
- A year here. A full year lasts just 12.8 Earth days.
By the numbers
- Size. About 2.9× the width of Earth.
- Volume. About 24.5 Earths could fit inside it.
- Mass. About 1.6× the mass of Earth.
- Your weight. You'd weigh about 0.2× your Earth weight standing here.
- Density. Less dense than water — drop it in a big enough ocean and it would float.
- Temperature. A scorching 380°C on average.
How we found it
- Discovery. Found by K2 using the transit method.
Cosmic context
- Crowded system. One of at least 6 planets orbiting its star.
Properties
- density gcc
- 0.4
- discovery facility
- K2
- discovery method
- Transit
- dist ly
- 660.7431
- eccentricity
- 0.062
- eq temp k
- 653
- insolation
- 51
- mass earth
- 1.63
- name
- K2-138 f
- orbital period days
- 12.7576
- radius earth
- 2.904
- sys num planets
- 6
How to see it
Like any astronomical target, K2-138 f 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 K2-138 f is an uncommon exoplanet
K2-138 f scores 30 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 4 science badges — Confirmed exoplanet, Sub-Neptune, Multi-planet system and Richly packed system — 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.