NGC 1427A, an irregular galaxy in Eridanus

 
NGC 1427A, an irregular galaxy in Eridanus

Image Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

NGC 1427A is a dwarf irregular galaxy of more than 20,000 light-years long that lies about 52 million light-years away from Earth in the constellation of Eridanus, while it is receding from us at roughly 2028 kilometers per second. It is the brightest dwarf irregular member of the Fornax Cluster, a group of 58 galaxies.

This small, blueish galaxy is comparable in size, luminosity and color to the Large Magellanic Cloud. It shows lots of young blue star clusters and pink star-forming regions with numerous hot, blue stars that have been formed very recently, throughout the galaxy.

Galaxy clusters, like the Fornax cluster, contain hundreds or even thousands of galaxies. Under the gravitational grasp of other galaxies in the Fornax cluster, NGC 1427A is speeding through the cluster’s intergalactic gas at around 600 kilometers (nearly 400 miles) per second. The arrowhead shape of the galaxy has been forged by its rapid, upwards motion through the cluster. Its swept back outline points toward the top of this picture – and that is indeed the direction the galaxy is moving as it travels toward the center of the cluster.

Within the Fornax cluster, there is a considerable amount of gas lying between the galaxies. When the gas within NGC 1427A collides with the Fornax gas, it is compressed to the point that it starts to collapse under its own gravity. The resulting pressure is triggering violent episodes of star formation. The tidal forces of nearby galaxies (probably the central Fornax galaxies NGC 1404 and NGC 1399), may also play a role in triggering star formation on such a massive scale.

The interactions with cluster gas and the other cluster galaxies during its headlong flight through the cluster will disrupt NGC 1427A within the next billion years, spilling its stars and remaining gas into intergalactic space within the Fornax cluster.

The disruption of objects like NGC 1427A, and even larger galaxies like our own Milky Way, is an integral part of the formation and evolution of galaxy clusters. Such events are believed to have been very common during the early evolution of the Universe, but the rate of galaxy destruction is tapering off at the present time. Thus the impending destruction of NGC 1427A provides a glimpse of an early and much more chaotic time in our Universe.

To the upper left of NGC 1427A is a background galaxy that lies some 25 times further away. At even greater distances background galaxies of various shapes and colors are scattered across this image.

The Hubble Space Telescope’s Advanced Camera for Surveys was used to obtain images of NGC 1427A in visible (green), red, and infrared filters in January 2003. These images were then combined by the Hubble Heritage team to create the color rendition shown here.

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