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Scale of Distance to Closest Stars
相關課程
- Before we start going off into things outside of our solar system
- I wanna take a few steps back because I found this neat picture of
- the sun over here, and the reason why at least in my mind it's kinda
- mindblowing it's because at this scale the sun is obviously still a huge object
- at this scale, the Earth would be roughly, and this is an approximation,
- roughly that big, so for me at least, this is mindblowing because this idea
- that our whole planet, everything we could fit into one of these kind of plasma flares
- coming off of the sun, and you can only imagine, we can't realistically
- be there but if you were in some type of protective capsule what it would be like
- to be in this type of an enviroment
- so I just thought this was kind of a fascinating concept, but anyway,
- with that out of the way, let's just think about what it means to be
- at the boundary of the Solar System, in the last video we explored the
- Oort Belt which was about, it started a little under 1 light year away from the Sun
- but depending on what you view as a boundary it could be something way
- further in or as far out as something like the Oort Cloud
- So if the Sun, well we see this things being ejected, but even in unseen ways
- unseen particles, super high energy electrons and protons are also
- being ejected from the Sun at super high velocities, 400 km/s, let me write that down
- 400 km/s
- and on Earth we're protected from this highly energetic particles
- because of Earth's magnetic field, but if you're on the surface of the Moon
- when the Sun is on top of the Moon, and you're in the dark side of the Moon
- you'll have direct contact with this, and you can imagine, not the best thing
- to hang around in too long, but the whole reason why I'm talking about this,
- this charged particles that are coming out at huge velocities
- from the surface of the Sun, these are considered the Solar Wind
- these are the Solar Wind, and I'll put the "Wind" in quotes
- 'cause it's really very different that out tradicional asociation of a nice breeze
- these are just charged particles that are going out at super high velocities from the Sun
- and 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 kinda comes in confrontation with the interstellar medium
- and this right here shows a depiction of that, so the Oort Cloud is way
- at least the edges of the dense part is way
- outside of this, as we saw this is just where Voyager I and Voyager II,
- 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 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
- farely large, so this is right here this heliopause right here, and I got this from
- Wikipedia, this is essentially where the velocity and the forces of the Solar Wind are
- counteracted, the preassure is so diluted at this point that it's counteracted
- by mainly the hydrogen and the helium that's in the interstellar kind of
- 'medium', that's just kind of out there, after this point it's not being ejected out anymore
- it's just kind of, there's this kind of 'pause' there, I guess you could say
- and Voyager I and Voyager II have essentially gotten pretty close to
- people believe, that 'pause' over there, and 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, you know, the area where you have the still objects out there
- and this is all, actually we haven't directly observed objects in the Oort Cloud,
- we think they're out there, and then maybe the most abstract definition would be
- the significant influence from the Sun's gravitational pull, so all of those ways
- are to imagine the extent of the Solar System, but they all kinda leave a gray area
- for what is and what is not in the Solar System, but my whole point here,
- what I wanna do is start explaining a little bit outside of the Solar System
- and just give you a sense of the scale as we just go to the closest start
- so if we go right over here, this shows our local neighbourhood
- from a stellar point of view, and even though this stars look pretty big, if you
- actually were to draw, this is our Solar System right here, but clearly,
- oh and you might be saying 'oh 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 it still wouldn't make up
- one pixel on the screen right here, what we see right here, which is a radius
- it's roughly a radius of about, give or take, a light year, this is roughly
- maybe the radius of the Oort Cloud, and 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, and that itself it's a huge, huge diameter, a huge distance away from the Sun
- and that wouldn't even make a pixel on this diagram right over here.
- But just to give you an idea of how far we are, we're a speck of a speck of a speck inside here,
- a pixel of a pixel in the center here, to make it from our Solar System, or in particular from Earth maybe
- to the nearest star, or maybe the nearest cluster of stars, the Alpha Centauri
- they're the nearest cluster of stars, there's 3 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 Proximus Centauri I think it's called,
- not Alpha Proximus, Proximus Centauri, so that's a much smaller star,
- but that's the closest star, and this whole cluster of stars, and they're the closest,
- is about 4.2 lightyears 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, or if this guys were to dissapear or blew up we wouldn't know it for 4.2 years
- and you might say 'hey, that's not too bad, we should take a trip over there and check them out
- and 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 lightyears is an unbelievably ridiculous
- distance, and just to give you a sense, the Voyager I and II, we talked about them
- in the last video and we an even see how far they've gotten, they've gotten
- pretty much to the heliopause, this guys are traveling at 60,000km/h
- which is the same thing as 17km/s, if we were able to get up to those type of velocities,
- and this guys got up to this type of velocities by leveraging the gravitational
- pull of some of the larger planets to keep accelerating, so this is
- a pretty hard velocity to actually reach, but if you were able to reach that velocity
- and go straight to the direction of the Alpha Centauri system, the closest starts to Earth,
- it would take you 80,000 years travelling at the same velocity as Voyager I, which is the fastest of
- the Voyagers, so it's a ridiculously long time, so we're gonna have to figure out some better way to
- do that.
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