I recently read a Scientific American magazine that had been gathering dust in my bedroom’s stack of reading materials. The issue contained an interesting article about how the universe is expanding. Of course, it has been known that the universe is expanding since the early 1900s when an astronomer named Edwin Hubble discovered this phenomenon based on his studies of the light emitted from distant galaxies. However, as described in the article, recent observations by a new generation of astronomers show that the expansion of the universe is accelerating. So, not only is the universe expanding, but it is expanding faster today than in the past. This is a very counterintuitive finding. I remember learning in college that large-scale gravitational forces might slow the expansion sometime in the distant future. Back then, textbooks speculated that the universe might even stop expanding or eventually collapse on itself. The findings described in the article were so revolutionary that the astronomers who performed the original research earned the 2011 Noble Prize in physics.
Reading this made me think of one of my favorite pictures of all time. In my opinion, it is the most important picture that virtually nobody knows about. It does not contain a sunrise or sunset or a mountain, but it captures billions and billions of stars and undoubtedly even more planets with their own sunrises, sunsets, or mountains beyond our imagination. The picture I’m talking about is what is known as an “extreme deep-field” image and it was taken by the Hubble Space Telescope. You probably know that the Hubble Space Telescope orbits the earth and has been a workhorse of astronomy research for almost 30 years. Of course, it is named after the astronomer that I mentioned earlier.
We have all seen pictures from the Hubble Space Telescope. The images brilliantly illustrate exploding stars, colliding galaxies, and other galactic marvels in glorious displays of light. While the primary goal of the images is to provide astronomers with information for new scientific insights, of course I just see the beauty in these pictures. If you are not familiar with pictures from Hubble, I encourage you to search the internet to explore the volumes and volumes of amazing pictures that have been produced by this remarkable camera. I think you will see the beauty in them too!
It goes without saying that the Hubble telescope is pointed at something when astronomers use it to take pictures. The subject might be a nebula or a star cluster, or one of the phenomenon I mentioned above. But for the picture I’m talking about, they pointed Hubble at nothing—nothing in our Milky Way, at least. It turns out that they really had to work hard to locate such a spot. This is because the Milky Way galaxy, our home galaxy, contains many clouds and other objects that block the view outside to the rest of the universe. It is sort of like being in the middle of a dense forest and trying to find a gap within the trees to provide a view outside the forest. In the case of the Hubble Space Telescope, the Milky Way is like a dense forest with very few gaps in the trees. And for this picture, the astronomers wanted to aim Hubble “through the gaps in the trees” to see what is outside our Milky Way. This is why they refer to this picture as a “deep-field” image in their terminology.
The Hubble astronomers successfully located a tiny section of outer space that is about one-tenth the width of the full moon and essentially devoid of Milky Way objects. Then they pointed Hubble at this area and collected data for days and days—50 days, to be exact, scattered over a period of about 10 years. If Hubble were a digital camera (it is), it would be like taking many pictures of the same subject for a decade with the cumulative time that the shutter is open totaling something like 550 hours. Of course, all this while Hubble is orbiting the earth at 17,000 miles/hour with no tripod! Yes, the photographer geek in me realizes that the Hubble Space Telescope is the most spectacular camera ever built!
After collecting all that data, the resulting picture is stunning. I’ve downloaded a copy of it from NASA’s website and shared it below. As you can see in the picture, that tiny section of empty space is not empty all! Instead, that space was filled with thousands of specks of light! This is important: virtually every little speck of light in this picture is an entire galaxy that is located outside our Milky Way galaxy. That is worth repeating: virtually each little speck of light is an entire galaxy that is located outside our Milky Way. In turn, since a galaxy contains billions and billions of stars, this picture represents hundreds of trillions of individual stars! Now, stay with me, but imagine if each tiny section of outer space contained a similar number of galaxies as those shown in the Hubble extreme deep-field image. Then, the universe as a whole would contain billions and billions of galaxies, each with billions and billions of individual stars. Now, keep hanging in there, but imagine further still that many of those stars are just like our own sun! How many sun-like stars are out there in the universe? How many planets are out there? The numbers quickly become too large to comprehend, but the implications regarding our place in the universe are staggering.
Human beings are capable of understanding many complex things, but I think the size of the universe is more than anyone can possibly fathom. Sure, the vocabulary of math and science can describe the scale of the universe, but I contend that no one really comprehends the size of it. And our earth, our planet, is a microscopic speck of cosmic dust in the infinite expanse of space. As I noted in a previous post: we are insignificant. And merely knowing that is very, very significant. Nothing demonstrates the significance of insignificance like Hubble’s extreme deep-field image. And that is why this picture is one of the most profound pictures ever created.
I hope you enjoy the accompanying picture as much as I do. I wish I could say that I took it. 🙂 I discussed a lot of technical stuff in this missive and I hope you enjoyed that as well. If you have any questions or if you find any mistakes, please let me know! If you’d like to learn more about Hubble’s extreme deep-field images, check out this website:
Image credit: NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa Cruz), R. Bouwens (Leiden University), and the HUDF09 Team