It’s a bottomless sky
The Hubble Ultra Deep Field. Source: S. Beckwith & the HUDF Working Group/HST/ESA/NASA. Click on the image for a nice high-resolution 19 MB version. It may take a minute to load, but once you have it you can have a boatload of fun getting lost among the jillions of distant and colorful galaxies. Of course, my wife would say I don’t need the picture to do that
Every now and again I like to post an astronomy image or video that, in my opinion, has nice spiritual resonances. If ever there was a photo of the sky that had such, it’s this one: It’s called the Hubble Ultra Deep Field, and it is the deepest (meaning most distant and faintest) image ever taken of the universe. Once you meditate on it while, it’s enough to knock your knickers off, if you were to wear knickers. I would like to share a little about what you’re looking at when you stand in front of this thing.
1. The area covered by the image is about one-tenth that covered by the full moon. That is, ten of these images put together would look as “big” as the moon as seen from your back yard. Or your front yard. Or anywhere else on Earth. The section of sky is in the southern constellation of Fornax, to the south and west of the more famous Orion.
2. Almost every spot you see on this image is a galaxy, which is a collection of anywhere from a million to a trillion stars. There are about 10,000 galaxies in the field. There ARE a few individual stars in the picture, though: These are the bright points of light with so-called “diffraction spikes” radiating from them. An example is the star near middle right; it carries the rather romantic name USNO-A2.0 0600-01400432 and is a pale yellow-white color. This star and the others in the field are part of our own Milky Way Galaxy and are in the extreme foreground. It’s like looking at a mountain range 100 miles away through a car window; the stars are like spots on the windshield, a few inches from your nose.
3. About 800 exposures were taken by the Advanced Camera for Surveys instrument on board Hubble. The total exposure time is just under 1 million seconds (about 11.5 days).
4. Perhaps the most important — and interesting — thing to know is that, as one looks further back in space, one is looking further back in time. When we look at the Moon we see it as it was a couple of seconds earlier; when we look at the Sun we see it as it was 8 minutes earlier; when we look at nearby stars we see them as they were a handful of years earlier; when we look at the closest galaxies we see them as they were several million years earlier. Light takes time to travel, is the point, and we can’t see anything until light from it enters our eyes. So when we look at the HUDF, we are seeing the nearest galaxies (like the beautiful spiral near the lower right-hand corner), which are perhaps several hundred million light years away, as they were hundreds of millions of years ago. And the most distant ones? We are seeing them as they were about 13 billion years ago! This is just a few hundred million years after the big bang. Thus, by moving from the most distant galaxies to the nearest ones, we can learn about how galaxies are built up over time; that is, we can study galactic evolution. When we look down this deep well of the sky, we are not only looking across unimaginable distances; we are looking deep into the past as well.
5. This patch of sky is not unusual in any way; we see the same basic picture no matter which direction we look. We will see different galaxies, to be sure, but the overall distribution of galaxy types and colors and distances will be the same.
6. A typical galaxy has about 100 billion stars in it, and this image contains 10,000 galaxies. Therefore there are about 10^15 (that’s 1,000,000,000,000,000) stars in this picture. Many of these stars, if not most of them, have planets orbiting them. What kind of life is has developed or is developing on these planets? How much extraterrestrial life are we looking at? How many advanced civilizations are contained in this wonderful image? Just a thought.
Before I sign off, I thought I’d share a few relevant links. First, there’s a nice scalable and interactive version. Next, a NASA site with animations. Over at APOD they have an infrared image of the same patch of sky. And here’s a fun 3D voyage through the image.
That’s all I have for now. If I think of other cool stuff to mention about the HUDF, I will add it to the list. I hope this helps each of you meditate a bit on how strange and surprising a place we have found ourselves living in. We didn’t even ask for it! It’s enough to freak you out a little, and I mean that in the best possible way.
There are 1 Comments to "It’s a bottomless sky"
So I started teaching my new course on galactic astronomy today (and the honors section of the course yesterday). In both cases I showed them the Hubble Ultra Deep Field, as well as the recent animation on the scale of the universe produced by the AMNH. It’s basically the Total Perspective Vortex from Hitchhiker’s Guide to the Galaxy. Makes you feel very small (which is a drastic understatement).
But as I told my student there is another way to look at it. When we take a picture like the HUDF, all that actually shows up on the film (well, the CCD chip) is some fuzzy patches of light. But we are able to interpret these fuzzy patches into the amazing picture of the universe that you describe above. It is the human mind which has constructed this picture, a picture we have many reasons for believing is an accurate representation of at least certain aspects of the actual universe.
I think this way of looking at the HUDF also carries an important spiritual message. How are we able to know such things about the universe? What does it tell us that we have been able to construct this amazing picture? Maybe it tell us something deep. Maybe even something ultra deep….