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Dead galaxy discovered by Hubble space telescope challenges galactic evolution theory


Theory of evolution of galaxies has been challenged by a new study that describes discovery of a distant dead galaxy using the Hubble space telescope and power of a “natural lens” in space.

Researchers say that when they discovered the galaxy 10 billion light years from Earth they were expecting a chaotic ball of stars formed through galaxies merging together. However, what they found was that the stars were born in a pancake-shaped disk. This effectively mean that some of the earliest so-called “dead” galaxies somehow evolve from a Milky Way-shaped disk into the giant elliptical galaxies we see today.

Astronomers involved with the study published in journal Nature say their finding is surprising because until now evidence have suggested that elliptical galaxies contain older stars, while spiral galaxies typically contain younger blue stars. The discovery of the dead galaxy means that some of these early “dead” disk galaxies must have gone through major makeovers to the point that not only changed their structure, but also the motions of their stars to make a shape of an elliptical galaxy.

The newly discovered remote galaxy is three times as massive as the Milky Way but only half the size. Rotational velocity measurements made with the European Southern Observatory’s Very Large Telescope (VLT) showed that the disk galaxy is spinning more than twice as fast as the Milky Way.

If we look back at the studies that have been made with respect to galactic evolution, almost all of them have assumed that structure of dead galaxies is similar to the local elliptical galaxies they will evolve into. While a direct observation of distant dead galaxies isn’t something that is technologically possible today, “gravitational lensing,” is something that helped astronomers observe the distant galaxy. A massive, foreground cluster of galaxies acts as a natural “zoom lens” in space by magnifying and stretching images of far more distant background galaxies. By joining this natural lens with the resolving power of Hubble, scientists were able to see into the center of the dead galaxy.

Why this galaxy stopped forming stars is still unknown. It may be the result of an active galactic nucleus, where energy is gushing from a supermassive black hole. This energy inhibits star formation by heating the gas or expelling it from the galaxy. Or it may be the result of the cold gas streaming onto the galaxy being rapidly compressed and heated up, preventing it from cooling down into star-forming clouds in the galaxy’s center.