Cosmology and astronomy
Hubble Image of Galaxies. Created by Sal Khan.
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- I'm thinking about buying a small telescope right now. But then again: I live in a big city, so, would I be able to see any stars at all, or only orange blur? What stars (and planets) could I expect to see in a perfect night sky with an off-the-shelf telescope? Can one recognize details of the planets (venus, jupiter, saturn, ...), or would they still be mere dots?(75 votes)
- Well, i live in a not particularly dark bit of England and have a 6" reflector and just the other night managed to see Saturns rings, the stormy colour bands of Jupiter and a glorious view of the Orion nebula as well as countless star clusters. My advice to you would be first find your local astronomy group and go out observing with them that'll give you a chance to try out a load of telescopes and get an idea of what you can see. also this gives you the opportunity to speak to some people who really know there stuff. if there's one thing astronomers love more than looking at the universe its talking about it so i'm sure they would be happy to help you. Most of the time you'll be looking at the faintest little blob of fuzzyness suspended upon a never ending darkness which some people get disappointed with, i tend to look at it in a different way. Each little photon, every little quanta sized packet of light has made an immense journey across the universe for millions or sometimes even billions of years. The end of this epic journey is the retina in the back of your eye, a million year quest to end up in my eyeball. That makes the view special everytime. Hope that helps(156 votes)
- Is it possible the birth of new galaxies in our time?(42 votes)
- Galaxies are not exactly objects(like stars or planets for example) but clusters of hundred of billions of stars. So if a bunch of stars suddenly clustered around a point or something, and maybe even started a SMG (SuperMassive Blackhole), then that would be a galaxy
One of the best ways to think about a galaxy being formed id probable when galaxies collide (The Milky Way and Andromeda will collide in 5 billion years from now). When galaxies collide, they throw of immense amounts of matter. Take the example of Andromeda and the Milky Way (Milky for now). When they crash, they will for an immense super galaxy (Andromeda is NOT a small galaxy), however, amounts of matter will be thrown off. If those chunks combine, it could form another galaxy, hence, giving a birth to a galaxy
Also, who knows what's happening at the site of the big bang? The 'point' could still be banging and throwing matter. after all, the universe IS expanding. so it could create more galaxies(50 votes)
- If we got a rocket to go faster than the speed of light what would we see if we some how got a picture of the outside space? In theory because we see the past at slower than light speed shouldn' t we be able to see the future? But how does the universe know whats going to happen?(7 votes)
- We can't go at the speed of light but if we could, then looking outside would be weird. In front, it would be extremely bright as compressed light waves blend together into jumbles of meaningless light that we won't be able to identify things in. Looking back, it would be pitch black.(19 votes)
- What other telescopes have been launched into space?(6 votes)
- There are dozens of orbiting telescopes, here are some of the more known ones.
Chandra is like Hubble except it detects x-rays.
Swift Gamma Ray Burst Explorer is extremely flexible and can see many forms of light.
COROT and Kelper search for extrasolar planets.
Spitzer detects infrared waves.
COBE took pictures of the cosmic microwave background(12 votes)
- Sal mentions that the universe is expanding, but I've also been told that the Andromeda and Milky Way galaxies will collide in 4-5 billion years. Shouldn't the two galaxies be moving away from each other?(11 votes)
- It is correct that the universe is expanding and also that the Milky Way and Andromeda galaxies will collide in 4-5 billion years but because of the gravity they're fastly coming to each other.(4 votes)
- So, why does the galaxy/star at the bottom of the screen in2:24look like a bloated plus sign? I haven't heard of galaxies with four perpendicular arms. Also, why does the sun sometimes look like it has straight arms when you look at it for a second or through video?
EDIT: thanks to branyon for linking a page to the diffraction spikes and thanks to everyone else as well/(6 votes)
- The object is a star, not a galaxy. The perpendicular arms are called "diffraction spikes" and are a result of the optical components in the telescope (Hubble Space Telescope for this specific case). Here is a quick web page that describes them: http://apod.nasa.gov/apod/ap010415.html, and has lots of cool images every day.(6 votes)
- If their still far away how can we tell it is a galaxy or star(8 votes)
- Galaxies are so bright and have billions of stars. A star is puny to a galaxy but BIG to us. A galaxy is HUGE! ! ! ! ! ! ! ! ! !(0 votes)
- I've heard some theories that the colors of hubble pictures are photo shopped to make the pictures more colorful, so are they really that colorful, or did they just add that in?(6 votes)
- hubble is black/white so they get a really powerful telescope and look at it through that other telescope then they add the colors they see(4 votes)
- i get bullied in school ):(5 votes)
- this is mind-blowing. im only one lesson in to this class and ive already had at least 5 existential crises(7 votes)
The whole point of this video is really just to look at, what in my mind is one of the coolest pictures ever taken by anything, and this was actually taken by the Hubble telescope and what they did is, they pointed the telescope at this area of our night sky and obviously the Hubble telescope, it's out in orbit, so it doesn't have to worry about all the interference from our actual atmosphere, so it gets a nice good look at things, but it's right over here, relative to the moon, and obviously the moon is moving around, but on that day, it was here, relative to the moon and they picked this location. They picked this location right over here because there weren't that many nearby stars there so it really allowed the telescope, because if there were nearby stars that light would've kind of outshone things that are behind it further away maybe perhaps galaxies. So just keep in mind everything you're going to see is in this little patch of the night sky, and I think the main point for showing the moon here. Obviously the moon is moving around so I'm not going to tell you which exact patch of sky this is. But to really give you an idea of how small of a patch of sky that really is. You really could've done this with any patch of sky, but in other patches of sky there wouldve been nearby stars that would've blocked things, but the galaxies are there, beyond that. The clusters of galaxies, and the super clusters of galaxies. So with that said out of the way, just remember everything we're talking about in this video is in this little patch of sky right over here. The whole point of this, once again like all of these videos is really to kind of just blow your mind. So this right here is what the Hubble telescope saw in that patch. Everything, everything that I'm showing you right here. I just want to be clear, some of these things are nearby stars, but most of these things are galaxies. That's a galaxy. That is a galaxy. That is a galaxy. That's a galaxy, and that's a galaxy. The reason I want to draw you this, obviously in the last video I showed you our local group, I showed you the Virgo super cluster, I showed you the kind of clusters of clusters and I even showed you the depiction of the observable universe. But what is amazing about this, is this is an actual picture. This is actually an image of a galaxy. Hey there is another galaxy. Oh look there's another galaxy up here. That you can keep doing that forever and this is just in that little patch of sky, and this is obviously not all of the galaxies of the universe. These are just the ones that we could see. There ones that might be even further, or there definitely are ones that are further back and their light is just even more. We could probably even focus on a patch of sky like that and see that many galaxies again. You can kind of keep, keep zooming in, but I just this thing, and I encourage you I mean there's so many unbelievable images you can look up. They're all on NASA's website, a lot of these are on Wikipedia. But these images are just unbelievable. You can see a galaxy, another galaxy, another galaxy, another galaxy. I suspect some of this stuff might actually be clusters of galaxies. Galaxy, another galaxy. And remember I'm just circling these galaxies, just left and right, and you kind of lose sight of what each galaxy actually is. These galaxies have hundred of billions of stars. That even from you know one pixel on these galaxies is unimaginable distance. Something that we could never, based with current technology, or even current science, we could ever hope to traverse in the lifetime of humanity. Not, much left in a lifetime of one individual. So these are just enormous things, and they're just an infinite number of them. So I just wanted to highlight this with you, and really just look at it. Its kind of breathtaking. Another galaxy right over there. I'm not going to keep doing it the whole day. I feel kind of bad for drawing on it, it kind of ruins the picture. But look at that, that's a nice looking galaxy right there. You got a bunch right over here. It really is just, you know. This video its probably the least dense with actual instruction, but hopefully the most dense with inspiration. Anyway, hopefully you enjoyed that. Let me just finish looking at the entire picture. I mean it just keeps going ,and going we can keep looking at it.