About HD 81817 c
HD 81817 c is a rare exoplanet. It lies about 877.8 light-years from Earth, has an equilibrium temperature near 1,199 K, spans roughly 12 Earth radii and weighs about 7,185.78 Earth masses.
Packed denser than solid iron.
Rare exoplanet 43 EP
HD 81817 c
RA 144.2716° · Dec 81.3263° · exoplanet
Score breakdown
· 5 badgesRare 46 pts → Epic
- Denser than iron +18
- Hot Jupiter +10
- Multi-planet system +6
- Confirmed exoplanet +5
- Gas giant +4
Total score 43
3 more points to reach Epic.
Badges
- Confirmed exoplanet · +5
- Gas giant · +4
- Hot Jupiter · +10
- Denser than iron · +18
- Multi-planet system · +6
Trivia
What makes it special
- Heavyweight. Packed denser than solid iron.
Could we get there?
- Verdict. Hopelessly far for any craft humanity can build today.
Getting there
- Aboard Voyager 1. ≈ 15.4 million years at Voyager 1's speed (17 km/s).
- Fastest probe ever. ≈ 1.4 million years even at the Parker Solar Probe's 192 km/s.
- At 10% light speed. ≈ 8778 years in a starship at a tenth of light speed.
- Distance. 878 light-years from Earth.
Look-back time
- Look-back time. The light you'd see left around the year 1148.
Saying hello
- Say hello. A radio message and its reply would take 1756 years round-trip.
Standing on it
- A year here. A full year lasts just 623 Earth days.
By the numbers
- Size. About 12× the width of Earth.
- Volume. About 1728 Earths could fit inside it.
- Mass. Roughly 7186× Earth's mass — about 22.6 Jupiters.
- Your weight. You'd weigh about 49.9× your Earth weight standing here.
- Density. Denser than solid iron.
- Temperature. Around 925°C — hotter than a self-cleaning oven.
How we found it
- Discovery. Found by Multiple Observatories using the radial velocity method.
Cosmic context
- Crowded system. One of at least 2 planets orbiting its star.
Properties
- density gcc
- 22.9
- discovery facility
- Multiple Observatories
- discovery method
- Radial Velocity
- dist ly
- 877.7706
- eccentricity
- 0.095
- eq temp k
- 1198.52
- insolation
- 337.2228
- mass earth
- 7185.7825
- name
- HD 81817 c
- orbital period days
- 622.978
- radius earth
- 12
- sys num planets
- 2
How to see it
Like any astronomical target, HD 81817 c 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 81817 c is a rare exoplanet
HD 81817 c scores 43 points on Spacedle's rarity scale, which places it in the rare tier. Another 3 points would lift it into a rarer tier.
That score comes from 5 science badges — Confirmed exoplanet, Gas giant, Hot Jupiter, Denser than iron and Multi-planet 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.