Hey, sky fans! Should that be capitalized? I’m not very good about keeping it consistent.
Hey, Sky Fans!
Let’s get right to it so I can get back to having some fried food with my family. It’s time for #4 on our list of 2016’s best natural satellites!
There are about 200 moons in our solar system, spread out across the major planets and dwarf planets. Jupiter leads the way with 67 by itself. Earth has the fewest of all of the planets with moons.
That kind of sounds like an ad for sugar-free gum: Four out of five dentists surveyed say of all the objects in the solar system that have moons, Earth is tied for having the fewest. You’re right, that’s sort of how math works. You can’t really have fewer than one moon while still having any at all. How do you have half a moon?
I can only think of four objects that have exactly one, and three—Makemake, the asteroid 243 Ida, and Eris—are dwarf planets. Tiny Ida’s even tinier moon, Dactyl, was the first asteroid discovered orbiting an asteroid.
My mind kept wandering out into the deepest parts of the solar system, though. I kept thinking about Eris, the object whose discovery in the early 2000s let to it and Pluto, rightly, being reclassified as dwarf planets. If there’s one thing that there never seems to be enough of in astronomy, it’s superlatives. Biggest this, iciest that. You know how it is.
Dysnomia, Eris’s moon, is the most distant natural satellite in the solar system. Eris orbits far off in the Scattered Disc, which is a region of the solar system that’s beyond the far-out Kuiper Belt, which, itself, is out beyond Neptune. Pluto is in the Kuiper Belt, and averages about 40 astronomical units from the Sun. An astronomical unit (AU) is a measure of distance equal to the average distance from the Earth to the Sun, about 92.9 million miles. Eris averages about 70 AU from the Sun.
Since Eris and Dysnomia are so far away, and are difficult to study, there’s a lot we don’t know about Dysnomia, but the fact that we know about it at all is what grabs me. The idea of being able to see something that size at that distance just makes my eyes widen. Plus, its name makes me feel like it’s saying it’s name means it has no name (that’s not really what its name mean).
So, thanks to the hard work of Hubble and the astronomers who use it, #5 on the list is Dysnomia!
Rest in peace, Carrie Fisher, and thank you.