New image reveals spiral galaxy’s secrets
Washington: Combination of data from NASA/ESA Hubble Space Telescope and observations by amateur astronomers has produced one of the best images yet of nearby spiral galaxy Messier 106.
Located a little over 20 million light-years away, practically a neighbor by cosmic standards, Messier 106 is one of the brightest and nearest spiral galaxies to our own.
Despite its appearance, which looks much like countless other galaxies, Messier 106 hides a number of secrets. Thanks to the new image, they are revealed as never before.
At its heart, as in most spiral galaxies, is a supermassive black hole, but this one is particularly active. Unlike the black hole at the center of the Milky Way, which pulls in wisps of gas only occasionally, Messier 106’s black hole is actively gobbling up material.
As the gas spirals towards the black hole, it heats up and emits powerful radiation. Part of the emission from the center of Messier 106 is produced by a process that is somewhat similar to that in a laser -- although here the process produces bright microwave radiation.
As well as this microwave emission from Messier 106’s heart, the galaxy has another startling feature -- instead of two spiral arms, it appears to have four.
Although the second pair of arms can be seen in visible light images as ghostly wisps of gas, as in this image, they are even more prominent in observations made outside of the visible spectrum, such as those using X-ray or radio waves.
Unlike the normal arms, these two extra arms are made up of hot gas rather than stars, and their origin remained unexplained until recently.
Astronomers think that these, like the microwave emission from the galactic center, are caused by the black hole at Messier 106’s heart, and so are a totally different phenomenon from the galaxy’s normal, star-filled arms.
The extra arms appear to be an indirect result of jets of material produced by the violent churning of matter around the black hole. As these jets travel through the galactic matter they disrupt and heat up the surrounding gas, which in turn excites the denser gas in the galactic plane and causes it to glow brightly.
This denser gas closer to the center of the galaxy is tightly-bound, and so the arms appear to be straight. However, the looser disc gas further out is blown above or below the disc in the opposite direction from the jet, so that the gas curves out of the disc -- producing the arching red arms.
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