About HD 128717 b
HD 128717 b is a rare exoplanet. It lies about 240.2 light-years from Earth, has an equilibrium temperature near 152 K, spans roughly 12.1 Earth radii and weighs about 6,293 Earth masses.
Packed denser than solid iron.
Rare exoplanet 36 EP
HD 128717 b
RA 219.0882° · Dec 57.5610° · exoplanet
Score breakdown
· 4 badgesRare 46 pts → Epic
- Denser than iron +18
- Eccentric orbit +9
- Confirmed exoplanet +5
- Gas giant +4
Total score 36
10 more points to reach Epic.
Badges
- Confirmed exoplanet · +5
- Gas giant · +4
- Eccentric orbit · +9
- Denser than iron · +18
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. ≈ 4.2 million years at Voyager 1's speed (17 km/s).
- Fastest probe ever. ≈ 375 thousand years even at the Parker Solar Probe's 192 km/s.
- At 10% light speed. ≈ 2402 years in a starship at a tenth of light speed.
- Distance. 240 light-years from Earth.
Look-back time
- Look-back time. The light you'd see left around the year 1786.
Saying hello
- Say hello. A radio message and its reply would take 480 years round-trip.
Standing on it
- A year here. A full year lasts about 9.4 Earth years.
By the numbers
- Size. About 12.1× the width of Earth.
- Volume. About 1772 Earths could fit inside it.
- Mass. Roughly 6293× Earth's mass — about 19.8 Jupiters.
- Your weight. You'd weigh about 43.0× your Earth weight standing here.
- Density. Denser than solid iron.
- Temperature. A frigid -121°C — colder than dry ice.
How we found it
- Discovery. Found by European Space Agency (ESA) Gaia Satellite using the astrometry method.
Cosmic context
- Wild orbit. Its highly elliptical path swings between scorching and frozen each lap.
Properties
- density gcc
- 19.5
- discovery facility
- European Space Agency (ESA) Gaia Satellite
- discovery method
- Astrometry
- dist ly
- 240.1682
- eccentricity
- 0.85
- eq temp k
- 151.9
- insolation
- 0.0892
- mass earth
- 6293.0025
- name
- HD 128717 b
- orbital period days
- 3420
- radius earth
- 12.1
- sys num planets
- 1
How to see it
Like any astronomical target, HD 128717 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 128717 b is a rare exoplanet
HD 128717 b scores 36 points on Spacedle's rarity scale, which places it in the rare tier. Another 10 points would lift it into a rarer tier.
That score comes from 4 science badges — Confirmed exoplanet, Gas giant, Eccentric orbit and Denser than iron — 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.