Scientists have revealed for the first time that galaxies can change their structure over the course of their lifetimes.
A team of researchers used the Hubble and Herschel telescopes to reveal how the majority of galaxies have undergone a major "metamorphosis" since they were formed in the Big Bang, Cardiff University reported. The researchers hope the new insights will help shed light on the processes that led to these changes.
"Many people have claimed before that this metamorphosis has occurred, but by combining Herschel and Hubble, we have for the first time been able to accurately measure the extent of this transformation," said Professor Steve Eales, from Cardiff University's School of Physics and Astronomy.
To make their findings, the researchers looked at about 10,000 galaxies included in the Herschel ATLAS and GAMA projects. The galaxies were classified into two main types: "flat, rotating, disc-shaped" galaxies similar to the Milky Way; and "large, spherical" galaxies containing a high number of disordered stars.
The findings revealed 83 percent of all stars that have formed since the Big Bang originated in disc-shaped galaxies.Only 49 percent of these stars remain in disc-shaped galaxies today, and the remaining exist in spherical galaxies. The results suggest a major metamorphosis occurred in which disc-shaped galaxies became spherical-shaped galaxies.
Researchers believe the metamorphosis occurs because of a number of catastrophic events, such as two disk-dominated galaxies staying too close to each other until gravity merges them into one single galaxy with a major pileup of stars. Another theory suggests the galaxies merged in a much more peaceful manner in which the stars formed a disc and gradually moved to the galactic center, creating a pileup.
"Galaxies are the basic building blocks of the Universe, so this metamorphosis really does represent one of the most significant changes in its appearance and properties in the last [eight] billion years," Eales concluded.
The findings were published in a recent edition of the Monthly Notices of the Royal Astronomical Society.
