The Universe we can see doesn’t go on forever. Everything we observe originated no more than 13.7 billion years ago, so even accounting for the expansion of the Universe, the farthest objects we can see are less than 46 billion light-years away. However, I could forgive you for thinking we can see forever, especially when we look at images like this:The Hubble eXtreme Deep Field (XDF) survey is the result of over 10 years of data, observing a single patch of sky roughly 1/15 the size of the full Moon (2 arcminutes, for the experts). The image encompasses 22.5 days worth of exposure time (though not all at once!), with the Hubble Space Telescope aimed at a dark spot in the constellation of Fornax. As with the earlier Hubble Deep Field (HDF) and Ultra Deep Field (HUDF)surveys, a lot of real science lies in this beautiful photo mosaic. Approximately 5,500 galaxies are within the field of view, with perhaps even more to be revealed via gravitational lensing.
As with most astronomical photos, the XDF survey draws together images using filters (in this case 8 separate but overlapping filters) to recreate the colors above. The image even includes infrared light, which our eyes can’t perceive, but which carries important information, so its inclusion is less to show what we could see than to demonstrate what Hubble can see—which is a much broader part of the spectrum.
On a more personal note, I get lost in images like the XDF. Nearly every object in this image is a galaxy—a huge gravitational island containing hundreds of billions of stars. That alone is a staggering thought, but perhaps even more striking is that we are looking back in time as well. The light from some of those galaxies left billions of years ago, perhaps before Earth formed—and we are just receiving that light now. Our unaided eyes can’t see any of them, but through the Hubble Space Telescope, we have a time machine of sorts, enabling us to peer into earlier times and far-off places.
We live in a beautiful Universe. Science can help us discover that beauty, and understanding it—far from detracting from its aesthetic value—enhances its joy and wonder.