Hey all, I spelt "Epimetheus" wrong in this tweet of some amazing image processing, so to make up for it, I'm gonna tweet a thread of little factoids about the moon.
1) it looks like a potato that's been swiss cheesed.
(This image was taken by Cassini (❤) in 2007. Credit: NASA/JPL/Space Science Institute)
2) it's small, only about 72 miles (or 116 km) across!
3) at about 94,000 miles (151,000 km) from Saturn, it takes just 17 hours to make one full orbit about the planet. Plugging these into a calculator tells me it has an orbital speed of ~55,000 km/h! (But wait---the distance thing gets really interesting because gravity is awesome)
4) Epimetheus has a dance partner. They swing each other throughout this dance so that they swap spots in their orbital game: Janus. Janus is a total potato.
(Image taken by Cassini (❤) in 2010. Credit: NASA / Jet Propulsion Laboratory / Space Science Institute)
(Yes I'll always put a ❤ in any time I mention Cassini. ❤ =') )
5) the two moons only differ by about 31 miles (50 km) in distance from Saturn, so that their gravitational interaction is strong enough to keep them in this "co-orbital resonance".
6) When one (let's say it's Epimetheus) is closer in, it orbits just a bit faster than the other (Janus) does. And here's where the distance thing gets interesting: this difference in orbital speed is such that it takes about 4 years for Janus to catch up to Epimetheus.
7) when the two get close, their gravitational attraction increases enough for them to sort of swap orbital angular momentum, which is when they swing each other and swap spots!
(It's a bit more involved than that since Janus is more massive. And Saturn has particles in its orbit, so Epimetheus and Janus tug on house too. Check out @elakdawalla's post on this gravitational dance, here: planetary.org/blogs/emily-la…)
8) so, not only is Epimetheus a cute swiss cheesed potato moon, but it has a friend to dance with throughout its journey around the ringed planet! =)
Missing some Tweet in this thread?
You can try to force a refresh.

Like this thread? Get email updates or save it to PDF!

Subscribe to Sophia Nasr 🏳️‍🌈
Profile picture

Get real-time email alerts when new unrolls are available from this author!

This content may be removed anytime!

Twitter may remove this content at anytime, convert it as a PDF, save and print for later use!

Try unrolling a thread yourself!

how to unroll video

1) Follow Thread Reader App on Twitter so you can easily mention us!

2) Go to a Twitter thread (series of Tweets by the same owner) and mention us with a keyword "unroll" @threadreaderapp unroll

You can practice here first or read more on our help page!

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just three indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member and get exclusive features!

Premium member ($3.00/month or $30.00/year)

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!