How long is a day on Eris?

So, How Long is a Day on Eris, Anyway?

Eris. It’s a name that just sounds distant, doesn’t it? And that’s fitting, because this dwarf planet hangs out way, way beyond Neptune, chilling in the scattered disc. It’s an icy little world, and honestly, still a bit of a mystery to us. But one thing we are starting to nail down is how long it takes to spin – in other words, how long a day is on Eris. Turns out, it’s around 25.9 hours. Pretty wild, huh? Almost like Earth!

Cracking the Code of Eris’s Spin

Now, figuring that out wasn’t exactly a walk in the park. I mean, think about it: Eris is something like 6.3 billion miles away. That’s so far that sunlight takes over nine hours just to get there! Being that distant and relatively small makes it tough to get a good look.

So, how did scientists manage to clock Eris’s rotation? Well, they used some clever tricks, like studying what we call “light curves.” Imagine watching a light bulb slowly dim and brighten. That’s kind of what they do, charting how Eris’s brightness changes over time. Those changes give clues about how fast it’s spinning. Pretty neat, right?

Dysnomia: Eris’s Partner in…Time?

And here’s another cool piece of the puzzle: Eris has a moon! We call her Dysnomia. By keeping an eye on Dysnomia’s orbit, we can learn a ton about Eris itself, like how massive it is. For a long time, the best guess was that Dysnomia took about 15.774 days to circle Eris. That helped scientists figure out that Eris is about 27% more massive than Pluto. Whoa!

But there’s a twist! Some researchers thought Eris might be spinning almost in sync with Dysnomia’s orbit, like maybe around 14.56 days. That’s a big difference, and it suggests that the relationship between Eris and Dysnomia is still evolving. You see, over billions of years, gravity can make planets and moons “lock” their spins and orbits together. It’s like they’re dancing to the same beat. But the latest data seems to point to the light curve period being the same as Dysnomia’s orbital period. So, the mystery continues!

Eris: The Goddess of…Dwarf Planets?

Eris wasn’t always a household name. It was discovered back in 2005 by Mike Brown and his team. And honestly, that discovery caused a huge ruckus. It kicked off a big debate about what really makes a planet a planet. Ultimately, it led to Pluto getting reclassified as a dwarf planet, along with Eris. Hence the name – Eris was the Greek goddess of discord and strife!

Eris is actually the ninth-biggest thing orbiting the Sun, and the sixteenth-biggest in the whole Solar System. We think it’s made of rock and ice, and it’s probably covered in a frosty mix of nitrogen and methane ice. It’s super reflective, too, bouncing back about 96% of the sunlight that hits it. That’s probably because its surface gets a fresh coat of ice every now and then, thanks to the temperature changes as it travels around the Sun.

Speaking of which, Eris takes a whopping 557 Earth years to orbit the Sun! And its orbit is really stretched out. At its closest, it’s “only” about 37.9 AU from the Sun (that’s astronomical units, or the distance from Earth to the Sun). But at its farthest, it’s way out there at 97.7 AU!

Even though we haven’t sent a spaceship to visit Eris yet, every new observation helps us understand this weird and wonderful dwarf planet a little better. And hey, maybe someday we’ll get a close-up view and solve all those mysteries once and for all!