Hubble finds tiny and giant galaxies in the process of merging

Gravitational interaction is triggering star formation in both galaxies.
By Laurel Kornfeld | Jul 29, 2017
NASA's Hubble Space Telescope has captured images of two local neighborhood galaxies merging, one a giant barred spiral and the other a tiny dwarf galaxy.

NGC 1512, the spiral, and NGC 1510, the tiny dwarf, have been in the process of merging for about 400 million years.

In spite of their major size differences, each galaxy has gravitationally affected the other, initiating star formation in both and slowly altering their appearances.

Barred spiral galaxies are so named because a central bar comprised of stars, gas, and dust runs across them. Raw materials required for star formation are channeled from the central bar into the galaxy's outer ring.

The Hubble image shows two bright blue-colored areas in NGC 1512, one an inner disk within the bar and the other an outer ring surrounding the galaxy; both of these are areas of active star formation.

Known as a circumnuclear starburst ring, the inner disk is estimated to have a diameter of 2,400 light years.

Scientists believe both the bar and the outer ring are the result of gravitational interaction between the large galaxy and its dwarf neighbor.

Previous Hubble observations of NGC 1512 have shown a second, calmer star-forming region in the outer ring, which is dotted with Hill regions, areas of ionized interstellar atomic hydrogen where stars formed relatively recently.

Beyond the outer ring, NGC 1512 extends even further, with features that appear to be malformed spiral arms surrounding NGC 1510.

The thin, arm-like tendrils may be composed of material stripped from the dwarf galaxy.

A 2015 observation of NGC 1512 indicated the outer regions of its spiral arms likely originated in an older galaxy that the spiral ripped apart.

Because galaxy mergers play a key role in galactic evolution, scientists seek to better understand the dynamics and processes that occur during these events.

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