What is the temperature of Eris?

What’s the Deal with Eris’s Temperature? It’s Colder Than You Think!

Eris. Ever heard of it? Officially, it’s 136199 Eris, but what you really need to know is that it’s a dwarf planet way, way out there, hanging out in the boonies of our solar system. As a trans-Neptunian object – basically, it chills beyond Neptune – it’s seriously cold. I’m talking face-numbingly, can’t-even-imagine cold. Let’s dive into just how frigid it gets on Eris, what makes it so darn cold, and what that means for its surface and maybe even an atmosphere.

Seriously, How Cold Are We Talking?

Okay, picture this: the temperature on Eris can swing from a bone-chilling -243°C to a slightly “warmer” -217°C. That’s -405°F to -359°F for those of us who prefer Fahrenheit. To put it mildly, you wouldn’t want to vacation there. This crazy temperature range? Blame Eris’s wild orbit, which sends it swinging closer and then much, much farther from the sun over its super-long 557-Earth-year journey around our star.

What Makes Eris So Incredibly Cold?

So, what’s the secret recipe for such extreme cold? A few things stack up against Eris:

• Distance, Distance, Distance: Eris is just plain far away from the sun. We’re talking about three times farther than Pluto! On average, it’s a staggering 10.1 billion kilometers (6.3 billion miles) away. At that distance, sunlight is basically a rumor, and Eris gets only a tiny trickle of solar warmth.
• A Wonky Orbit: Eris doesn’t just circle the sun in a nice, neat circle. Nope, its orbit is seriously eccentric, meaning it’s stretched out like a rubber band. At its closest, it’s “only” 38.4 AU (astronomical units) from the sun. But at its farthest? A whopping 97.7 AU! That huge swing in distance means a huge swing in temperature.
• Super Reflective Surface: Now, here’s a weird one. Eris is super shiny! It has an albedo of about 0.96. Think of it like this: it’s like a giant, icy mirror reflecting almost all the sunlight that hits it. So, instead of soaking up the sun’s energy and warming up, it just bounces it all back into space.

Ice, Ice, Maybe a Little Atmosphere?

All that cold has a major impact on what Eris looks like and what’s going on up there:

• Frozen Solid: The surface is probably mostly nitrogen ice, with a sprinkle of methane and carbon monoxide thrown in for good measure. Some studies even suggest that much of the surface has pure methane ice on it, with the rest being a mix of methane, nitrogen, water ices, and something called “ice tholin”. That high albedo we talked about? Some scientists think it’s because the surface ice is constantly being refreshed as Eris’s temperature changes during its orbit.
• Poof, There Goes the Atmosphere: Here’s a crazy thought: Eris might have an atmosphere sometimes! Because it’s so cold, any atmosphere it could have pretty much freezes and falls as snow. But, as Eris gets a bit closer to the sun, some of that ice might warm up just enough to turn into a gas, creating a super-thin, temporary atmosphere. Pretty wild, huh? The JWST didn’t find any ethane, which supports the idea that Eris’s surface is always refreshing itself.

The Bottom Line?

Eris is one seriously cold place, with temperatures ranging from a teeth-chattering -243°C to -217°C. Its distance from the sun, its crazy orbit, and its super-reflective surface all play a part in making it so frigid. And those temperatures? They shape everything about the dwarf planet, from its icy surface to its maybe-sometimes atmosphere. We still have a lot to learn about this distant, icy world, and I, for one, am excited to see what we discover next!