Today’s guest post is by Dr. Mario Livio, Hubble astrophysicist and author of the blog “A Curious Mind.” A version of this post appeared previously on Dr. Livio’s blog.
During the Christmas season of 1995, the Hubble Space Telescope was pointed for 10 consecutive days at an area in the sky not larger than the one you would see through a drinking straw.The region of sky, in the Ursa Major constellation, was selected so as to be as “boring” as possible — empty of stars in both our own Milky Way galaxy and in relatively nearby galaxies.The idea was for Hubble to take as deep an image of the distant universe as possible.The resulting image was astounding. With very few exceptions, every point of light in this image is an entire galaxy, with something like 100 billion stars like the Sun.
The original Hubble Deep Field image.
Detailed analysis revealed that the very remote galaxies were physically smaller in size than today’s galaxies, and that their morphologies were more disturbed. Unlike the grand-design spirals or smooth elliptical shapes that we see in relatively close galaxies, the distant objects look like train wrecks. Both of these observations fit nicely into the ...