Using NASA's Hubble Space Telescope, an international team of astronomers discovered that mature-looking galaxies existed more than 11.5 billion years ago when the Earth was only about 2.5 billion years old.
NASA's Hubble Space Telescope has been very useful in studying the evolution and anatomy of many galaxies. In a new study, researchers from the University of Massachusetts, Amherst, found that "mature" galaxies existed earlier than previously believed, as early as 11.5 billion years ago. The discovery was made using two cameras - Wide Field Camera 3 (WFC3), and Advanced Camera for Surveys (ACS). Researchers also studied observations made by the Hubble's Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS).
Data from CANDELS allowed the researchers to analyze about 1,671 galaxies in detail. Lead researcher BoMee Lee found that mature galaxies existed even before the shapes and colors of these extremely distant young galaxies fit the visual classification system introduced in 1926 by Edwin Hubble
The Hubble Sequence categorizes galaxies into two prominent groups - elliptical and spirals, with lenticular galaxies as a transitional group. This categorization is based on a galaxy's ability to form new stars, which determines its colors, shape and size.
"Another piece of the puzzle is that we still do not know why today 'red and dead' elliptical galaxies are old and unable to form stars, while spirals, like our own Milky Way, keep forming new stars," Mauro Giavalisco, advisor to Lee, said in a press statement. "This is not just a classification scheme, it corresponds to a profound difference in the galaxies' physical properties and how they were formed."
Galaxies as large as the Milky Way are very few in the Universe. This makes it difficult to gather enough information on matured stars to properly characterize them. Galaxies that formed as early as the Milky Way appear to be mostly irregular systems with no clearly defined morphology.
After the study, Lee and her colleagues confirmed that all galaxies this far back fitted into the sequence that dates back to a mere 2.5 billion years after the Big Bang.
"Clearly, the Hubble Sequence formed very quickly in the history of the cosmos, it was not a slow process," Giavalisco said. "Now we have to go back to theory and try to figure out how and why."
