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These are just charged particles that are going out at super high velocities from the sun. I'm even going into the idea of the solar wind because to some degree, they can help us with one definition of maybe the limits of the solar system. And that's the limits of how far the solar wind is getting before it kind of com... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
This right here shows a depiction of that. So the Oort cloud, at least the edges of the dense part of it, is way outside of this. As we saw, this is just where Voyager 1, Voyager 2, if we wanted the orbit of Sedna, it would be something like, the close part would be something over here and then it would go out. But the... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
But the Oort cloud is much, much further out. So if you look at this kind of view of the solar system as the extent of the solar wind, it's much smaller than the Oort cloud, but it's still fairly large. So this is right here, this heliopause right here, and I got this from Wikipedia. This is essentially where the veloc... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
This is essentially where the velocity and the forces of the solar wind are counteracted. The pressure is so diluted at this point that it's counteracted by mainly the hydrogen and the helium that's in the interstellar medium that's just kind of out there. After this point, it's not really being injected out anymore. T... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
There's this kind of pause, I guess you could say. Voyager 1 and Voyager 2 have essentially gotten pretty close to, people believe, that pause over there. So that's one view of the edges of the solar system. There's never going to be any hard edge to it. Another view would be something like the Oort cloud, the area whe... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
There's never going to be any hard edge to it. Another view would be something like the Oort cloud, the area where you have the still objects out there. This is all actually, we haven't directly observed objects in the Oort cloud. We think that they are out there. Then maybe the most abstract definition would be a sign... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
We think that they are out there. Then maybe the most abstract definition would be a significant influence from the sun's gravitational pull. All of those ways are to imagine the extent of the solar system, but they all kind of leave a gray area for what is and what is not in the solar system. My whole point here, what... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
My whole point here, what I want to do is start exploring a little bit outside of the solar system and just give you a sense of the scale as we just go to the closest star. If we go right over here, this shows our local neighborhood from a stellar point of view. Even though these stars look pretty big, if you actually ... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
You might be saying, oh, maybe that's the sun. No, the sun, if you were to draw it here, it wouldn't even make up one pixel. In fact, the entire orbit of Pluto, everything inside of it, still would not make up one pixel on the screen right here. What we see right here, which is a radius of about, give or take, a light ... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
What we see right here, which is a radius of about, give or take, a light year, this is roughly maybe the radius of the Oort cloud. We saw in the last video how huge that was, especially relative to the radius of, say, Pluto's orbit, which is roughly like that. That itself is a huge, huge diameter or a huge distance aw... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
That wouldn't even make a pixel on this diagram right over here. Just to give you an idea of how far we are, we're a speck of a speck of a speck inside here, of a pixel of a pixel in the center here. We're in the center here to make it from our solar system, or in particular from Earth maybe, to the nearest star, or ma... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
They're the nearest cluster of stars. There's three stars, Alpha Centauri A, which is the largest, Alpha Centauri B, and then there's one that you can't observe with the naked eye, Alpha Proximus, or I think it's Proximus Centauri, I think is what it's called, not Alpha Proximus. Proximus Centauri. That's a much smalle... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
That's a much smaller star, but that's the closest star. You can view it as this whole cluster of stars right here. They're the closest. It's about 4.2 light years away. Or another way to think about it, if someone were to shine a light on one of these planets, and assuming that light could get to us, it would take 4.2... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
It's about 4.2 light years away. Or another way to think about it, if someone were to shine a light on one of these planets, and assuming that light could get to us, it would take 4.2 years to get to us. If these guys just disappeared or blew up, we wouldn't know it for 4.2 years. We'd say, hey, that's not too bad. We ... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
We'd say, hey, that's not too bad. We should take a trip over there and check them out, see if there are any other people there that we can meet and exchange technologies with or whatnot. But this is a huge distance. Just this 4.2 light years is an unbelievably ridiculous distance. Just to give you a sense, the Voyager... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
Just this 4.2 light years is an unbelievably ridiculous distance. Just to give you a sense, the Voyager 1 and 2, we talked about in the last video, and we can even see how far they've gotten. They've gotten pretty much to the heliopause. These guys are traveling at 60,000 kilometers an hour, which is the same thing as ... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
These guys are traveling at 60,000 kilometers an hour, which is the same thing as 17 kilometers per second. If we were able to get up to those type of velocities, and these guys got up to those type of velocities by leveraging the gravitational pull of some of the larger planets to accelerate and keep accelerating. Thi... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
But if you were able to reach that velocity and go straight in the direction of the Alpha Centauri system, the closest stars to Earth, it would take you 80,000 years traveling at the same velocity as Voyager 1, which is the fastest of the Voyagers. It's a ridiculously long time. We're going to have to figure out some b... | Scale of distance to closest stars Scale of the universe Cosmology & Astronomy Khan Academy.mp3 |
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