About HD 21520 b
HD 21520 b is a trash exoplanet. It lies about 258.3 light-years from Earth, has an equilibrium temperature near 637 K, spans roughly 2.7 Earth radii and weighs about 17.7 Earth masses.
About 2.7× the width of Earth.
Trash exoplanet 14 EP
HD 21520 b
RA 51.6403° · Dec -43.6137° · exoplanet
Score breakdown
· 3 badgesTrash 15 pts → Common
- Confirmed exoplanet +5
- Sub-Neptune +5
- Found by TESS +4
Total score 14
1 more point to reach Common.
Badges
- Confirmed exoplanet · +5
- Sub-Neptune · +5
- Found by TESS · +4
Trivia
Could we get there?
- Verdict. Hopelessly far for any craft humanity can build today.
Getting there
- Aboard Voyager 1. ≈ 4.5 million years at Voyager 1's speed (17 km/s).
- Fastest probe ever. ≈ 403.4 thousand years even at the Parker Solar Probe's 192 km/s.
- At 10% light speed. ≈ 2583 years in a starship at a tenth of light speed.
- Distance. 258 light-years from Earth.
Look-back time
- Look-back time. The light you'd see left around the year 1768.
Saying hello
- Say hello. A radio message and its reply would take 517 years round-trip.
Standing on it
- A year here. A full year lasts just 25.1 Earth days.
By the numbers
- Size. About 2.7× the width of Earth.
- Volume. About 19.6 Earths could fit inside it.
- Mass. About 17.7× the mass of Earth.
- Your weight. You'd weigh about 2.4× your Earth weight standing here.
- Temperature. A scorching 364°C on average.
How we found it
- Discovery. Found by Transiting Exoplanet Survey Satellite (TESS) using the transit method.
Properties
- density gcc
- 1.35
- discovery facility
- Transiting Exoplanet Survey Satellite (TESS)
- discovery method
- Transit
- dist ly
- 258.3416
- eccentricity
- 0
- eq temp k
- 637
- insolation
- 25.7431
- mass earth
- 17.7
- name
- HD 21520 b
- orbital period days
- 25.1292
- radius earth
- 2.697
- sys num planets
- 1
How to see it
Like any astronomical target, HD 21520 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 21520 b is a trash exoplanet
HD 21520 b scores 14 points on Spacedle's rarity scale, which places it in the trash tier. Another 1 point would lift it into a rarer tier.
That score comes from 3 science badges — Confirmed exoplanet, Sub-Neptune and Found by TESS — 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.