Astronomers have made a breakthrough in understanding the mystery behind the burning out of a number of elliptical galaxies back when the universe was fairly young.

The discovery was brought to light after scientists gathered and analyzed the data collected by the Hubble Space Telescope regarding burned out galaxies. There are numerous compact elliptical galaxies scattered throughout the universe. However, many of these galaxies have something in common. Back when the universe was still around 3 billion years old, these "red and dead" galaxies suddenly stopped producing new stars. Unlike galaxies that are still active in producing new stars, these burned "red and dead" galaxies are characterized by a reddish color.

"We at last show how these compact galaxies can form, how it happened, and when it happened. This basically is the missing piece in the understanding of how the most massive galaxies formed, and how they evolved into the giant ellipticals of today," said Niels Bohr Institute cosmology and astrophysics professor Sune Toft. "This had been a great mystery for many years because just 3 billion years after the big bang we see that half of the most massive galaxies have already completed their star formation."

Our home galaxy is around 12 billion years old but it is still actively producing new stars. While "red and dead" galaxies are a lot smaller, NASA astronomers believe that they used to be just as massive as our own galaxy when they were younger. Once these galaxies stopped producing new stars, however, they started to contract and become more dense.

"This means that the density of stars was 10 times greater," said Toft. "Further more, the galaxies were already dead, so they were no longer forming new stars. It was a great mystery."

Based on the latest findings from Toft and his colleagues, these burned out galaxies were initially starburst galaxies. A starburst galaxy is a type of galaxy that underwent a period of rapid star formation. These galaxies consumed vast amounts of gas in the early life of the universe to quickly form stars. After burning out, many of these galaxies merged together to form the giant elliptical galaxies that we see today. Astronomers were able to reach these conclusions after studying data gathered by Hubble Space Telescope as well as a number of ground-based telescopes.

The data gathered by Hubble has brought about numerous discoveries about the early universe. However, scientists are also looking forward to the completion of the new James Webb Space Telescope (JWST), which is currently undergoing construction. Once completed, the JWST will be a hundred times more powerful than Hubble.