Galaxy Messier 106, located a little over 20 million light-years away, is one of the brightest and nearest spiral galaxies
to our own. Despite its appearance, which looks much like countless
other galaxies, it has 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 seen here.
Despite carrying his name, Messier 106 was neither discovered nor
catalogued by the renowned 18th century astronomer Charles Messier.
Discovered by his assistant, Pierre Méchain,
the galaxy was never added to the catalogue in his lifetime. Along with
six other objects discovered but not logged by the pair, Messier 106
was posthumously added to the Messier catalog in the 20th century.
Amateur astronomer Robert Gendler
retrieved archival Hubble images of M 106 to assemble a mosaic of the
centre of the galaxy. He then used his own and fellow astrophotographer
Jay GaBany's observations of M 106 to combine with the Hubble data in
areas where there was less coverage, and finally, to fill in the holes
and gaps where no Hubble data existed.
The center of the galaxy is composed almost entirely of Hubble data taken by the Advanced Camera for Surveys, Wide Field Camera 3, and Wide Field and Planetary Camera 2 detectors. The outer spiral arms are predominantly HST
data colourised with ground-based data taken by Gendler's and GaBany's
12.5-inch and 20-inch telescopes, located at very dark remote sites in
New Mexico, USA. Gendler was a prizewinner in the recent Hubble's Hidden
Treasures image processing competition.
Source: The Daily Galaxy via ESA/Hubble Information Centre
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