For 10 straight days in 1995, Hubble stared at a tiny and nearly empty patch of sky near the Big Dipper. The telescope gathered all the light it could, slowly building a picture. What emerged — the Hubble Deep Field — revealed galaxies fainter than had ever been seen before. The light from some of these has traveled for 10 billion years to reach us.
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00:00The Hubble Space Telescope is an outstanding time machine in a sense.
00:29Because, of course, in astronomy, anything we look at in space, we're seeing it as it was when the light from that object, be it a planet, a star, or a galaxy, began its journey to us.
00:42Now, normally, we don't really think about that when we're just looking at the night sky.
00:48But it's incredibly important for our studies with the Hubble Space Telescope to realize that when we're looking at a galaxy, we're seeing it as it was millions of years ago, sometimes billions of years ago.
01:01It's taken that long for the light to get to us.
01:31One of the neat things about the Hubble Ultra Deep Field, and one of the things that made it so unique, was how long it took us to take that image.
01:44There's an exposure time that's expressed. I think it's 11.2 days. It's a very, very long exposure time.
01:49But probably what's more important is how many orbits it took us to do that.
01:53400 orbits of Hubble data to take that image. That's a lot of orbits.
02:00It was a lot of Hubble time. You only get 15 orbits a day. To take 400 orbits and say, we're going to observe this one spot in the sky for 400 orbits, and I think the results from the science, I mean, it was amazing.
02:12What they saw was spectacular.
02:15We see some of the faintest objects showing up in these images, and those faint objects are often distant galaxies.
02:23These deep fields have revealed visually to us a universe absolutely teeming with galaxies, hundreds of billions of galaxies.
02:32In one deep field alone, we can see a thousand of these little smudges of light, which are distant galaxies.
02:39By doing that, we can compare galaxies that are shining to us from billions of light years away with galaxies closer to us, or even to our own Milky Way, and see if they're similar or different.
02:53What Hubble has revealed is that the universe has, in fact, changed over these billions of years of time.
03:00We looked at the darkest part of the sky, a very small part of that, and we were amazed at how many galaxies we found.
03:08And we continue to go back to that portion of the sky to even increase that visibility.
03:15And we've seen tens of thousands of galaxies.
03:18Just, it's amazing.
03:21Hubble spent two weeks taking pictures of empty places in the sky, and they saw they weren't empty at all, they were thousands and thousands of galaxies.
03:28In astronomy, there's what we knew before Hubble, and now there's what we know after Hubble. They're so different.
03:33Basically, every page of an astronomy textbook now says something about discoveries made with Hubble. Every page.
03:41Hubble has given us this picture of the universe evolving over billions of years of time into a place where now we have galaxies with plenty of stars and interesting chemical makeup.
03:53So this is something that I'm grateful to the Hubble Space Telescope for opening our eyes to.