Space telescopes map globular clusters and ancient galaxies
The Spitzer and Hubble telescopes in Earth orbit use their different qualities to peer very deeply and very precisely into the depths of space. Hubble mapped a relatively nearby globular cluster over several years and analyzed the motions and masses of the stars clustered there; Spitzer spotted the oldest, most distant galaxies ever seen.
The globular cluster observed by the Hubble telescope in the constellation Toucan is one of the richest in stars in the southern sky. Using the high-resolution Hubble optics, the astronomers recorded the movements of around 15,000 stars in the cluster over a period of seven years and analyzed the masses of the objects. As it turns out, light stars are accelerating and moving toward the edge of the globular cluster, while massive suns gather in the center.
Such a "mass segregation" of the stars in globular clusters was only suspected, but not proven. One of the causes of the sorting is collisions between stars, which are statistically more common in the dense center of the cluster than further out. During the investigations, Hubble was also able to unmask 23 unusually hot and bright stars, which, as products of precursors that collided and thereby merged, moved more slowly than lower-mass average stars in the peripheral region.
The Spitzer Space Telescope looked much deeper into space with its highly sensitive infrared camera and spotted the most distant galaxies that have ever been studied in more detail at a distance of about 12.7 billion light years. From this distance, light reaches us from a time 700 million years after the Big Bang. Both objects were probably between 50 and 300 million years old at the time. So they must be among the first galaxies to be born around the end of the so-called "dark ages" of the universe, which lasted until about half a billion years after the Big Bang. In this early age of space, the early stars and galaxies were still eclipsed by an omnipresent nebula of hydrogen gas.
Astronomers have only very few galaxies from this period as objects of study. The next generation of space telescopes should remedy this and detect a larger number of such galaxies from the early days of the universe. The researchers believe that their number must be higher than previously ascertainable: Otherwise, the radiation pressure of the sparsely scattered stars and galaxies would hardly have been sufficient to rupture the dense curtain of hydrogen gas, which is what the current theory assumes.
