New Delhi: The 8.2 metre optical-infrared Subaru telescope located at the summit of Maunakea in Hawaii has captured a spectacular image of the polar ring galaxy designated as NGC 660 at a distance of 130 million lightyears in the constellation of Pisces. There ‘polar ring’ in the galaxy is a ring structure that is nearly perpendicular to the main disc of the galaxy. The stars in the ring are likely to have been stolen from a galactic neighbour during an interaction about a billion years ago. The complexity of the structure are revealed by the intersections of the dark lanes of gas and dust between the disc of the galaxy and its polar ring.
Gas and dust are the raw material from which baby stars are born, and the ring contains energetic light pouring out of baby stars, encouraged by the interaction in the past. The central bulge of the galaxy is lopsided, and is believed to contain significant amount of dark matter. The visible stars in the galaxy cannot be sufficiently massive to maintain the structural integrity of the galaxy, suggesting the presence of a mysterious invisible substance, or dark matter. There is a supermassive black hole lurking in the core of NGC 660, that erupted with the energy of 660 supernovas or dying stars in late 2012.
Polar Ring Galaxies and Dark Matter
There are only about 100 polar ring galaxies known. In such galaxies, the rings of stellar nurseries brimming with the light of newborn stars act as natural probes moving through the halos of galaxies, providing scientists with the valuable opportunity of mapping the distribution of dark matter. The polar ring is under the gravitational influence of both the main disc of stars in the galaxy, as well as the dark matter in its halo. The alignment of the ring in relation to the rotation of the ring allows scientists to better understand the combination of gravitational tugs, and subsequently map the distribution of dark matter. NGC 660 is sitting in a field of even more distant galaxies of all shapes and sizes, some of which are interacting.
