How Small Our Solar System Really Is

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Our solar system may be physically large, but in the grand scheme of things it is actually surprisingly small. Find out how small our solar system really is with help from an astrophysics professional in this free video clip.

Part of the Video Series: Moons & Planets
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Video Transcript

Hi, my name is Eylene Pirez, and I'm an astrophysicist and this is "how small our solar system really is." So, the best way to figure out how small something really is is to compare it with the rest of the universe. So, first, let's talk about the solar system and the components of the solar system, and where do we mark the end of the solar system. So, the end of the solar system, some people refer as to Neptune, but it is actually not true because we have the ort cloud which is where the comets come from and they're still orbiting the sun. So, let's mark the end of the solar system where the gravitational pull of the sun no longer is strong enough to have anything orbiting it. And, the radius, the distance from the sun to the ort cloud is 50,000 astronomical units. And, to be clear, one astronomical unit is the distance from Earth to the sun. So, the entire radius from the sun to the ort cloud is 50,000 times that distance. And, if you look at it because of the orbit, it goes both ways, so the entire diameter of the solar system will be twice the amount of that, so it would be 100,000 astronomical units. Now, where is the nearest star? The nearest star is Alpha Centuri, and that is four point four light years away, meaning that you can fit the solar system about two point six times between the sun and Alpha Centuri. So, it's very, very far away. Now, let's put it in perspective with the entire galaxy. So, our galaxy is the Milky Way, and where are we in the Milky Way? We are about one third into the arm, so right here, is our solar system. Now, how big is our actual galaxy, compared to us? So, here, we even have to drop the units of astronomical units because it no longer makes sense to talk about anything in astronomical units because this is way bigger than anything in the solar system. So, it actually, the diameter, the size of the disk if you were to look at a galaxy sideways, is 100,000 light years across. So, that's very, very large, and we are practically just a spec along the arm. Now, let's put how big is our galaxy compared to others, and how small are we compared to the whole universe? So, the nearest galaxy to us is Andromeda, and let's call this "Andromeda." And, this is the Milky Way. The distance between them is 2,538,000 light years. That means we can fight our entire galaxy over two times across from them. So, it's very, very far away, and that's the nearest galaxy. Now, it's been estimated to have at least 500 billion galaxies in the entire universe, and this is the closest one. That means that in terms of how small we really are, we are a grain of sand in an ocean. It's really, the scaling, the system between the solar system and the rest of the universe is very large. My name is Eylene Pirez, and I'm an astrophysicist and this is "how small our solar system really is."


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