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Last time we talked about the orbits of the Earth and our Moon. But today we're going to go a little bigger... well, a lot better. Did you know that there is a massive black hole at the center of our galaxy? Or that Pluto's orbit is really... weird? Today, Sabrina talks about these things and more on Crash Course Kids.

This first series is based on 5th-grade science. We're super excited and hope you enjoy Crash Course Kids!

///Standards Used in This Video///
5-PS2-1. Support an argument that the gravitational force exerted by Earth on objects is directed down. [Clarification Statement: “Down” is a local description of the direction that points toward the center of the spherical Earth.] [Assessment Boundary: Assessment does not include mathematical representation of gravitational force.]

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Producer & Editor: Nicholas Jenkins
Cinematographer & Director: Michael Aranda
Host: Sabrina Cruz
Script Supervisor: Mickie Halpern
Writer: Kay Boatner

Executive Producers: John & Hank Green
Consultant: Shelby Alinsky
Script Editor: Blake de Pastino

Thought Cafe Team:
Stephanie Bailis
Cody Brown
Suzanna Brusikiewicz
Jonathan Corbiere
Nick Counter
Kelsey Heinrichs
Jack Kenedy
Corey MacDonald
Tyler Sammy
Nikkie Stinchcombe
James Tuer
Adam Winnik
     You already know how objects, like the moon and artificial satellites, manage to orbit the earth. But there's all kinds of stuff up there orbiting other stuff that's not the earth. So, how do those orbits in space work? Are they the same as here at home or different? Or maybe... both!

     Now as much as I enjoy our little chats, unfortunately I don't have the time to talk about every single object in space that orbits something else and explain how their orbits work.
So how about we just go over a few of the important kinds of orbit instead.

     Lets begin with what were most familiar with. And look at how and why the Earth orbits the sun. The sun might just be a medium sized star, but its gravity is strong enough to hold several planets in orbit. Not to mention countless comets, asteroids, and other things. And the planet orbits the sun sort of the same way the moon or artificial satellites orbit the Earth. It travels in a nearly circular path around the star. Completing the whole trip every 365 days. 

     But why do we orbit the sun and not the other way around? Well, lighter objects tend to orbit heavier ones. And the sun is the heaviest object in our solar system. Its about 1000 x heavier than Jupiter, our largest planet, and certainly heavier than Earth. So the earth, the lighter object in this scenario is easily drawn towards the larger object, the Sun,  by its intense force of gravity.

     As we learned earlier though, the earth doesn't totally get sucked into the sun, because its moving fast enough around it to avoid that very hot and probably very horrible fate. That's why the earth plus the other planets and all kinds of space rocks orbit around the sun.

     Okay, lets zoom out a little more. Why does our whole galaxy orbit a black hole?  What? You didn't know? Well its true, but its nothing to be freaked out about. Lets start by defining some of those terms. You know what a sun is, but what is a galaxy, and what is a black hole?  

     A galaxy is a group of stars, gas, and dust bound together by gravity. Our sun is just one of billions of stars that are hanging out together in what scientists call the milky way galaxy. If it shares its name with a chocolate bar, you know its gotta be a good galaxy!

     And a black hole is a object that has a gravitational pull stronger than anything else in space. Its so strong, even light can't escape it. That's why they say its black. Think of it like a bottomless pit swallowing up whatever other objects get near it.

     Our milky way galaxy has a black hole at its center. But don't freak out. Luckily Earth is located thousands and thousands light years away from this black hole. So we wont be swallowed up by it. But we are close enough to it that the mass of stars, planets, dust, and gas inside of our galaxy combined with the ginormous mass of this black hole, holds us in our orbit. So for us on Earth, the black hole is actually a good thing. 

Okay, so bringing things back to our solar system. You know why everything in it orbits our sun. But does everything orbit it in the same way?

Not so much. Lets visit one of our dwarf planets. Which has a super odd orbit, at least when compared to the other planets.

The eight main planets tend to orbit the sun in a relatively circular way in the same imaginary plane, or level.  But the orbit of the dwarf planet Pluto is weird. Because not only is it off center from the sun, but its also not on the same plane. depending on where it is on the path around the sun, it can be on a higher or lower level than the other eight planets. 

     Pluto! You rebel. So why does it do that?

     Well while orbiting the sun, Pluto passes through a orbital path of another planet. Because of its strange orbital path, Pluto is actually sometimes closer to the sun than Neptune is. It actually crosses Neptune's orbit. When this happens, Neptune's gravitational pull forces Pluto in a lower orbit for a short period before it swings back into its higher orbit.

     So gravity has a lot to do with Pluto's odd orbit. And its proof that not everything in our solar system orbits the sun in the same way

     Lets bring this back to our big question.  How do other orbits in space work? Well they work a lot like things that do orbit the earth.  And also...they sometimes don't.

     Each object in space follows orbital patterns we can sometimes predict. But there are always oddballs out there that keep us on our toes. So don't ever let me catch you saying space is boring.