Which exoplanet has the most eccentric orbit?
The most eccentric orbit known belongs to HD 20782 b, at an eccentricity of 0.950, a path so stretched that the planet swings in close enough to roast and back out far enough to freeze on every circuit. Everything about HD 20782 b →
| # | World | Eccentricity | Distance |
|---|---|---|---|
| ★ 1 | HD 20782 b | 0.950 | 117 ly |
| 2 | HD 28254 b | 0.950 | 180 ly |
| 3 | HIP 66074 b | 0.948 | 116 ly |
| 4 | TIC 241249530 b | 0.941 | 1,058 ly |
| 5 | HD 80606 b | 0.932 | 217 ly |
| 6 | GJ 3222 b | 0.929 | 59.5 ly |
| 7 | HD 80869 b | 0.924 | 279 ly |
| 8 | HD 26161 b | 0.922 | 133 ly |
| 9 | Kepler-1704 b | 0.920 | 2,725 ly |
| 10 | HD 4113 b | 0.899 | 137 ly |
| 11 | BD+63 1405 b | 0.880 | 124 ly |
| 12 | TOI-6716 b | 0.880 | 61.6 ly |
| 13 | HD 76920 b | 0.878 | 600 ly |
| 14 | HD 98649 b | 0.852 | 138 ly |
| 15 | GJ 2126 b | 0.850 | 124 ly |
| 16 | HD 108341 b | 0.850 | 160 ly |
| 17 | HD 128717 b | 0.850 | 240 ly |
| 18 | HD 156846 b | 0.850 | 156 ly |
| 19 | KIC 3526061 b | 0.850 | 1,309 ly |
| 20 | K2-312 c | 0.844 | 358 ly |
| 21 | HR 5183 b | 0.840 | 103 ly |
| 22 | TOI-4504 b | 0.840 | 1,117 ly |
| 23 | Kepler-1656 b | 0.838 | 606 ly |
| 24 | WASP-53 c | 0.837 | 657 ly |
| 25 | Kepler-419 b | 0.833 | 3,299 ly |
Showing the top 25 of 2,175 that qualify.
Eccentricity runs from 0, a perfect circle, to just under 1, a path so elongated the planet barely returns. Earth's is 0.017, near enough to circular that our seasons come from axial tilt rather than distance. A world at 0.9 spends most of its year far out in the cold and then whips through its closest approach in days, with the starlight it receives changing by a factor of a hundred or more.
These orbits are measured from the shape of a star's velocity wobble, which is one of the most reliable things a spectrograph can extract, so the numbers here are trustworthy in a way that masses and radii often are not. Disputed rows are excluded. What could unseat this record: eccentric planets are easiest to spot in long radial-velocity campaigns, and each new decade of monitoring reaches further out.
Which exoplanet has the most eccentric orbit?
The most eccentric orbit known belongs to HD 20782 b, at an eccentricity of 0.950, a path so stretched that the planet swings in close enough to roast and back out far enough to freeze on every circuit.
What does an eccentricity of 0.9 actually feel like?
Like a year with a furnace at one end and a freezer at the other. At closest approach the planet may be receiving a hundred times the starlight it gets at its furthest point, so an atmosphere would be violently redistributed on every pass. Nothing in our solar system comes close: even Pluto only reaches 0.25.
How do planets end up on orbits like this?
Usually by a gravitational fight. A close pass with another giant planet, or a long-term tug from a distant companion star, can trade a circular orbit for a stretched one and sometimes throw the loser out of the system entirely. An eccentric giant is often the surviving evidence of a violent history.
Which planet in our solar system has the most eccentric orbit?
Mercury, at 0.206, among the eight planets, though Pluto beats it at about 0.25. Both are nearly circular next to the worlds on this table.
Keep exploring: all records · the widest orbit known · the longest year known