Science

NASA's Hubble Space Telescope Shed New Light on How Dead Galaxies Evolve

NASA's Hubble Space Telescope Shed New Light on How Dead Galaxies Evolve”

It is also one of the factors that contributed to experts thinking that spiral galaxies are younger and the earliest dead galaxies were elliptical.

This was a surprise, seeing as how astronomers did not expect to see this so early in the Universe.

Acting as a "natural telescope" in space, the gravity of the extremely massive foreground galaxy cluster MACS J2129-0741 magnifies, brightens, and distorts the far-distant background galaxy MACS 2129-1 (top box). It had stopped star formation a few billion years after the big bang. From astronomers' observations, older galaxies that have stopped producing stars take on an elliptical shape with star motions that are unpredictable, different from the Milky Way and other younger galaxies. Although three times as massive as the Milky Way, it is only half the size.

"This new insight may force us to rethink the whole cosmological context of how galaxies burn out early on and evolve into local elliptical-shaped galaxies", Dr. Toft said.

According to NASA, detecting such a galaxy from the universe's early history challenges what astronomers know about the evolution and formation of galaxies.

Combining rotational velocity measurements from the ESO's Very Large Telescope (VLT) with archival data from the Cluster Lensing And Supernova survey with Hubble (CLASH), they were able to determine the size of the galaxy, mass, and age as well as its (defunct) rate of star formation.

What they found was puzzling.

This is the first direct observational evidence that at least some of the earliest so-called "dead" galaxies-where star formation stopped-somehow evolve from a Milky Way-shaped disk into the giant elliptical galaxies we see today. This transition is largely thought to occur through mergers, which randomize the orbits of the stars in the resulting galaxy, transforming it from an ordered disk into an elliptical shape. However, the newly discovered ancient dead galaxy is spiral shaped and does not have the usual blue hue.

This finding is surprising because old, dead galaxies have always been thought to be elliptical rather than disk-shaped.

The galaxy in question, called MACS 2129-1, lies approximately 10 billion light-years away from Earth. But that could arise from the fact that astronomers have long assumed that distant dead galaxies look like their local universe counterparts.

"Speed limits also seem to differ somewhat between MACS 2129-1 and the Milky Way". Scientists are uncertain as to why this happens though they theorize it could be caused by an active galactic nucleus that releases high levels of energy that heat up and expel gases from which stars would form.

Toft's team hopes that with the launch of the James Webb Space Telescope, they'll gain a more powerful tool to see such faraway, hard-to-resolve objects without relying exclusively on lensing.



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