How Galaxies Took Shape
The first clumps of matter to form in the universe began to pull themselves together within a few hundred million years after the Big Bang. Each of these giant clouds of gas and dust included an enormous amount of material, aggregating perhaps a trillion times the mass of our Sun. Within the first billion years or so after their formation, these newly formed galaxies had given birth to their first generation of stars. But even these youngest galaxies are sites of star death as well as star birth. Within a few million years after the first galaxies had formed, the most massive of the galaxies' earliest generation of stars had already burnt themselves out. These stars exploded as supernovas to seed their galaxies with the heavy elements synthesized within their nuclear-fusing cores.
To observe galaxies as they form and during their earliest youth requires infrared-detecting telescopes. Except for the most distant ones, young galaxies reveal themselves in the light from their newly formed blue stars. The expansion of the universe shifts all the light from young galaxies toward the red end of the spectrum, so that today we observe as red the light that their stars emitted as blue billions of years ago. These young galaxies, so distant that their light must travel billions of light-years to reach us, can be observed with a new generation of advanced telescopes on the ground and in space. Ground-based telescopes can observe the portions of the infrared domain closest to visible light, making highly detailed spectroscopic measurements using complex instruments too large and heavy to launch into orbit.
Read More About The Giant Segmented Mirror Telescope (GSMT)