Which exoplanet has the longest year?
The confirmed exoplanet with the longest year is COCONUTS-2 b: a single orbit of its star takes about 1,100,616 years. Everything about COCONUTS-2 b →
| # | World | Year length | Distance |
|---|---|---|---|
| ★ 1 | COCONUTS-2 b | 1,100,616 years | 35.5 ly |
| 2 | CFHTWIR-Oph 98 b | 22,012 years | distance unknown |
| 3 | Oph 11 b | 19,986 years | 444 ly |
| 4 | VHS J125601.92-125723.9 b | 15,880 years | 41.4 ly |
| 5 | b Cen AB b | 4,901 years | 320 ly |
| 6 | HR 8799 b | 465 years | 135 ly |
| 7 | HD 143811 AB b | 320 years | 446 ly |
| 8 | HIP 81208 C b | 285 years | 481 ly |
| 9 | Pluto | 248 years | 0.0 ly |
| 10 | Charon | 248 years | 0.0 ly |
| 11 | HD 105618 c | 211 years | 229 ly |
| 12 | HR 8799 c | 189 years | 135 ly |
| 13 | Neptune | 165 years | 0.0 ly |
| 14 | Triton | 165 years | 0.0 ly |
| 15 | PZ Tel b | 120 years | 154 ly |
| 16 | PDS 70 b | 119 years | 369 ly |
| 17 | HD 153557 d | 111 years | 58.5 ly |
| 18 | HR 8799 d | 101 years | 135 ly |
| 19 | HD 12235 c | 99.5 years | 104 ly |
| 20 | HD 72659 c | 97.2 years | 169 ly |
| 21 | bet Pic d | 90.9 years | 64.4 ly |
| 22 | HIP 54515 b | 90.3 years | 270 ly |
| 23 | HD 11505 b | 89.4 years | 127 ly |
| 24 | HIP 39017 b | 84.9 years | 216 ly |
| 25 | Uranus | 84.0 years | 0.0 ly |
Showing the top 25 of 5,979 that qualify.
The longest confirmed years belong to worlds orbiting so far out that no one has ever watched them complete a single orbit: the period comes from the physics of the measured orbit rather than a stopwatch. Disputed rows are excluded.
For comparison, Neptune takes about 165 years to circle the Sun; the worlds on this table make that look brisk. What could unseat this record: directly imaged giants at extreme separations, whose orbits are pinned down a fraction at a time.
Which exoplanet has the longest year?
The confirmed exoplanet with the longest year is COCONUTS-2 b: a single orbit of its star takes about 1,100,616 years.
How long is the longest year?
COCONUTS-2 b takes about 1,100,616 years to complete a single orbit. Nobody has ever watched it finish one, and nobody will: the number comes from the physics of the measured orbit rather than from waiting.
How is an orbit measured if it has never been seen to complete?
From the geometry. Measure how far the planet sits from its star and how heavy the star is, and Kepler's third law gives the period directly. A short arc of observed motion is enough to pin the orbit down.
What is it like on a planet with a year that long?
Cold and dark. A world takes that long to orbit only if it is enormously far out, where its star is a bright point rather than a disc and delivers a tiny fraction of the light Earth receives.
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