The star collections known as galaxies formed much sooner in the early universe than previously estimated, according to an analysis of data from the Hubble Space Telescope. Galaxies were well established within 2.5 billion years of the big bang.
European Space Agency/NASA/ESA Hubble Space Telescope/Handout via Reuters
Galaxies appear to have matured much sooner in the early universe than previously estimated, adding intriguing twists to the history that astronomers are compiling of the growth and evolution of these vast collections of stars.
Using data gathered by the Hubble Space Telescope, a team of scientists found that galaxies of all sizes had fallen into two main shapes – disks and spherical – by 2.5 billion years after the big bang (an enormous release of energy that cosmologists say gave rise to the universe humans observe today).
The analysis by BoMee Lee at the University of Massachusetts at Amherst and her colleagues clearly shows that these galactic geezers not only were common some 11 billion years ago, but also had emerged as a distinct group within a couple of billion years after the earliest known galaxies formed, says Mauro Giavalisco, an astronomy professor at UMass Amherst and Ms. Lee's PhD adviser.
The challenge to understanding galaxy evolution: Spherical galaxies essentially are "red and dead." Their stars are almost as old the universe. And some process has quenched their star formation – a process that could involve supermassive black holes at their galactic centers or the cumulative effect of intense star formation prior to becoming spherical galaxies.
The new analysis "provides compelling evidence that quenching is fast and incredibly effective in spheroids," Dr. Giavalisco says. Now researchers have to figure out why.
The results stem from the Hubble Space Telescope's CANDELS project, short for the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. It's the largest observing program in the storied observatory's history. Its main objective is to track the evolution of galaxies from less than 1 billion years after the big bang through today.