Astronomy Science

Giant, ‘Dead’ Galaxy Puzzles Astronomers

Giant, ‘Dead’ Galaxy Puzzles Astronomers

We may often find it difficult to observe objects in the distant universe. The objects can be seen only through a magnifying glass. Astronomers located MACS 2129-1, a galaxy cluster using the Hubble Space Telescope. The MACS 2129-1 galaxy cluster is considered as a dead galaxy as it has stopped making new stars a few billion years ago. This galaxy is disk-shaped, unlike other galaxies that appear like a fuzzy ball of stars.

Giant, ‘Dead’ Galaxy Puzzles AstronomersMACS 2129-1, a massive disk-shaped dead galaxy next to Milky Way. (Image Source)

An article published in the journal Nature describes the galaxy to be half the size of the Milky Way but three times massive. The galaxy has red stars spinning fast almost two times the speed of the stars orbiting the center of our galaxy. Astronomers observed this through a phenomenon called as the gravitational lensing. Gravitational lensing happens when a massive object like a galaxy cluster bends the light from an object in the distance traveling towards the earth and magnifies the image on the sky. Based on the data received from the Cluster Lensing and Supernova survey with Hubble (CLASH), the astronomers found that the galaxy can measure the ages of the stars along with its total stellar mass and rate of star formation.

Astonishing Results of MACS 2129-1

Disk-shaped galaxies like ours make stars throughout their youth. These galaxies appear blue and have bright stars before turning into red and dead galaxies. When galaxies die, they get an elliptical shape because of mergers and randomizing of the star orbits. Thus, old galaxies are elliptical balls of stars and not coherent disks.

Giant, ‘Dead’ Galaxy Puzzles AstronomersDisk-shaped galaxy (Image Source)

According to the lead researcher, Sune Toft of the Dark Cosmology Center at the Niels Bohr Institute, University of Copenhagen, “this new insight about the galaxy makes us think about how the galaxies burn out early and turn into local elliptical shaped galaxies.”

Giant, ‘Dead’ Galaxy Puzzles AstronomersCloseup of M31 and one of its companion galaixes, an elliptical galaxy called M32 (Image Source)

The question that arises here is the reason that leads to this galaxy’s burn out and retaining its disk shape. Although the exact cause is not known, the possibility is that of an active central supermassive black hole or streams of cold gas flowing into the galaxy may have led to the prevention of the birth of new stars.

Astronomers assume that distant dead galaxies resemble their local universe counterparts. However, MACS 2129-1 is the only exception. Since distant galaxies are hard to be seen, these assumptions of the astronomers can be incorrect.
Toft adds that since the scientists were unable to resolve them, the early dead galaxies could be disks. Toft and his team hope that with the launch of the James Webb Space Telescope, the astronomers will gain a powerful tool to view the faraway and hard-to-resolve objects without relying only on the lensing technology.

Galaxies similar to the MACS 2129-1 will give ideas to the astronomers on galaxy formation and their evolution. In fact, it will also help them understand the reason behind the abrupt stop of star formation in these galaxies.


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