M106

Also known as NGC 4258, Messier 106 was discovered by Pierre Méchain in 1781. It is a spiral Seyfert II galaxy in the northern constellation of Canes Venatici (the Hunting Dogs), and is about 22 to 25 million light-years away from Earth. M106 is one of the largest and brightest nearby galaxies, similar in size and luminosity to the Andromeda Galaxy. The galaxy is about 80,000 light-years across and receding from us at nearly 500 km/sec; and like most galaxies, it will continue to disappear from view as the Universe expands.

M106 is famous, however, for something that our Galaxy doesn’t have – two extra spiral arms that glow in X-ray, optical, and radio light. These anomalous arms are not aligned with the plane of the galaxy, but instead intersect with it. The arms seen in this new composite image of NGC 4258, where X-rays from NASA’s Chandra X-ray Observatory are blue, radio data from the NSF’s Karl Jansky Very Large Array are purple, optical data from NASA’s Hubble Space Telescope are yellow and blue, and infrared data from NASA’s Spitzer Space Telescope are red.

In 1995, investigations with the Very Large Baseline Array radio telescope evidenced that M106 is possibly the home of a massive dark object: 36 million solar masses apparently reside within a volume of about 1/24 to 1/12 light year radius (27,000 to 54,000 AU) – then one of the densest matter concentration ever detected. Typical in grand spiral galaxies, dark dust lanes, youthful blue star clusters, and pinkish star forming regions trace spiral arms that converge on the bright nucleus of older yellowish stars. Seen here in red hues, sweeping filaments of glowing hydrogen gas seem to rise from the central region of the galaxy, evidence of energetic jets of material blasting into its disk. The jets are likely powered by matter falling into a massive central black hole. The dense disk around this object works as a maser (Microwave Amplifier by Stimulated Emission of Radiation, i.e. a microwave laser).

A new study of these anomalous arms made with Spitzer shows that shock waves, similar to sonic booms from supersonic planes, are heating large amounts of gas – equivalent to about 10 million Suns. What is generating these shock waves? The Chandra X-ray image reveals huge bubbles of hot gas above and below the plane of the galaxy. These bubbles indicate that much of the gas that was originally in the disk of the galaxy has been heated to millions of degrees and ejected into the outer regions by the jets from the black hole. Researchers estimate that all of the remaining gas will be ejected within the next 300 million years – very soon on cosmic time scales – unless it is somehow replenished. Because most of the gas in the disk has already been ejected, less gas is available for new stars to form. Because NGC 4258 is relatively close to Earth, astronomers can study how this black hole is affecting its galaxy in great detail. The supermassive black hole at the center of NGC 4258 is about ten times larger than the one in the Milky Way, and is also consuming material at a faster rate.

Credits: NASA, Universe Today, Wikipedia.