Which planet has the most flattened orbit or most eccentric orbit?

The Wonkiest Orbit in the Solar System: A Tale of Flattened Paths

Ever wondered which planet has the most squashed, stretched-out orbit? Well, in astronomy lingo, we’re talking about eccentricity. Think of it this way: a circle is a perfect “0” on the eccentricity scale. Anything above that, up to 1, is an ellipse – an oval shape. The closer you get to 1, the more flattened the orbit becomes. So, who’s the winner (or loser?) in this cosmic race?

Our Solar System’s Oddball

Turns out, Mercury takes the cake, or should I say, the flattened pancake. Its eccentricity clocks in at roughly 0.2056. Now, that might not sound like much, but compared to Earth’s nearly circular path (a measly 0.0167), Mercury’s orbit is noticeably oval. Venus is even more circular, with an eccentricity of about 0.0068. This wacky orbit means Mercury’s distance from the Sun varies quite a bit, leading to some wild swings in temperature. Imagine roasting one minute and shivering the next – Mercury’s life in a nutshell!

Now, before you jump in with “What about Pluto?”, you’re right, Pluto used to hold this title. Before its demotion to dwarf planet status, Pluto’s orbit was even more eccentric, clocking in at 0.248. It also has a seriously tilted orbit compared to the other planets – over 17 degrees off the main plane. Pluto may be a dwarf planet, but it still has a more eccentric orbit than any of the current eight planets.

But wait, there’s more! Beyond the main planets, things get even weirder. Take Eris, another dwarf planet chilling out in the Kuiper Belt. Its eccentricity is around 0.44. That’s a seriously stretched-out path! It swings from 37.8 astronomical units (AU) from the Sun at its closest, all the way out to 95.5 AU at its farthest. Talk about a long commute!

Then there’s Sedna, way out there, with an extreme eccentricity of 0.855.

And let’s not forget comets! These icy wanderers often have incredibly eccentric orbits, some almost reaching a value of 1. Halley’s Comet, a familiar face in our skies, has an eccentricity of 0.967. Some comets even have eccentricities greater than 1, meaning they’re on a one-way trip out of the solar system. Comet C/1980 E1 has the largest eccentricity of any known hyperbolic comet of solar origin, with an eccentricity of 1.057.

Exoplanet Extremes

But hold on, the real craziness happens beyond our solar system. When we look at exoplanets – planets orbiting other stars – we find some truly bonkers orbits. One example is HD 20782 b, an exoplanet with an eccentricity of about 0.96! This planet’s orbit is so elongated, it’s practically comet-like. It zooms far away from its star before whipping around for a super-close encounter. It’s like a cosmic slingshot!

Why Should We Care?

So, why all this fuss about eccentricity? Well, a planet’s orbit shape can have a huge impact on its climate, seasons, and whether it could even support life. Imagine living on a planet where one half of the year is scorching hot and the other is freezing cold! Understanding these orbital quirks is key to figuring out how planetary systems work and whether other worlds might be habitable. It’s just another piece of the puzzle in our quest to understand the universe and our place in it.