Celestial objects with interesting orbits

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Some objects with orbits that I find interesting:

Ferdinand (Uranus XXIV)
Nereid (Neptune II)
Neso (Neptune XIII)
Comet Hale-Bopp
90377 Sedna
2015 TG387 ("The Goblin")

Wow, I looked up Ferdinand's NASA page, I love how it was named after the Tempest!

What, exactly, makes these orbits interesting to you?

They're just real-universe examples of Keplerian/Newtonian physics, after all.

the first one is a moon that has an orbit that is both highly elliptical, and is retrograde (the moon moves the wrong way)

Some of the objects listed are transneptunian dwarf planets (recently discovered cousins of Pluto, but even farther out than Pluto). Some of these objects have highly oval, and eccentric orbits.

Transneptunian objects are also somewhat comet like, and some of the objects listed above are also comets.

Comets are notorious for having extremely elliptical and eccentric orbits, and also for having orbits at a high angle to the ecliptic (the plane of the Earth's orbit around the Sun). All of the eight planets orbit in (more or less) the same plane as the earth and, as each other, and all orbit on (more or less) the same plane as the equator of the Sun. Pluto is at somewhat of an angle to the ecliptic in its orbit. But comets come into the solar system from every crazy angle from above and below the ecliptic.

(does some looking up.) I had no idea Nereid has such a spectacular orbital eccentricity! If I've understood that right, its orbit is an ellipse 7 times as long as it is wide, which is not what you expect from a moon. Most of what I've read about the Neptune system focuses on Triton, a very large moon in a retrograde orbit.

I remember hearing about the discovery of Sedna, and feeling a sense of vertigo at just how cold, tiny and distant that world was. Pluto is close to us by comparison.

Just looked up Sedna.

Its at 85 AU distance from the Sun as we speak. At its closest its 76 AU, but it goes out to 937 AU. An AU being the distance from the Earth to the Sun. A very eccentric orbit. Like 12 to 1. Also its titled at 11 degrees to the ecliptic. And its orbit takes eleven thousand years to complete.

sedna's calendars are as thick as a phone book

145,000th of May: gaseous nitrogen season begins. Clocks go fowards to Sedna Summer Time.

Yes. Its summertime on Sedna.

Well...its not quite analogous to summer on earth. The change of seasons here on earth is caused by the tilt of the planet. We are actually slightly closer to the sun when its winter here in the northern hemisphere.

But Sedna's orbit is SO extremely elliptical that it would have to be a lot warmer now than when its at its farthest point in its orbit.

So its now summer time when the livin is easy on Sedna. Even though its colder there than on Pluto (only like 40 AUs from the Sun). And in five thousand years you might wanna take a winter vacation from Sedna to the balmy beaches of Pluto!

I don't believe there is data about Sedna's obliquity, for now at least, but that would definitely influence the seasonal temperature discrepancy (like you said). Another factor would be presence and composition of an atmosphere, but it is not confirmed. Many of the gases were are familiar with being part of an atmosphere are well-below freezing point on Sedna. A hazy atmosphere on Sedna?
This article discusses the possibility of a neon atmosphere!

And as it is summer there at this point in time, some ice-tholin mixtures, N and Ch4 ices will likely sublime.

Also, if humans wanted to send a probe or any spacecraft to it, our best chance would be in 2075-2076, when Sedna is at its perihelion.

Two from this list, Sedna and "The Goblin", along with the slightly less remote 2012 VP113, were mentioned in this article today: https://www.theguardian.com/science/202 ... nth-planet

Apparently, there's a whole group of Extreme Trans-Neptunian Objects with elongated orbits like that, with their furthest points from the Sun skewed towards one side of the Solar System. This could be due to the influence of an undiscovered planet with a mass somewhere between Earth's and Neptune's. Both the trend and the explantion for it are disputed, but it's an excitingly plausible idea.