How some galaxies formed rapidly in early universe

In a boost to the theory that some galaxies in early universe grew up in a hurry, astronomers have discovered 15 mature galaxies at a record-breaking average distance of 12 billion light years - when the universe was just 1.6 billion years old.

Most of the galaxies that have been observed from the early days of the universe were young and actively forming stars.

An international team of astronomers have now discovered galaxies that were already mature and massive in early days.

"The newly discovered galaxies must have formed very rapidly in roughly one billion years, with explosive rates of star-formation. The rate of star formation must have been several hundred times larger than observed in the Milky Way today," explained lead author Caroline Straatman from Leiden University in the Netherlands.

The team, including Eric Persson and Andy Monson from Pennsylvania-based Carnegie Mellon University, used deep images at near-infrared wavelengths to search for galaxies in the early universe with red colours.

"In the new near-infrared light images, the galaxies are easily measured, from which it can be inferred that they already contained as many as 100 billion stars on average per galaxy," added principal investigator Ivo Labbe.

The finding raises new questions about how these galaxies formed so rapidly and why they stopped forming stars so early.

Another big question is what caused the galaxies to mature at such a young age and if some dramatic event might have caused premature aging.

The galaxies were discovered using Magellan Baade Telescope at Carnegie's Las Campanas Observatory in Chile.

Using special filters to produce images that are sensitive to narrow slices of the near-infrared spectrum, the team was able to measure accurate distances to thousands of distant galaxies at a time, providing a 3D map of the early universe.

Today, the universe is filled with galaxies that have largely stopped forming stars, a sign of galactic maturity.

But in the distant past, galaxies were still actively growing by consuming gas and turning it into stars.

This means that mature galaxies should have been almost non-existent when the universe was still young, said the finding published in the Astrophysical Journal Letters.