A Hybrid Galaxy
What happens when a massive elliptical galaxy and a spiral galaxy meet? In the case of the galaxy Centaurus A, the spiral galaxy gets ripped apart! The stunning new image of Centaurus A, also known as NGC 5128, reveals more about the nature of interacting galaxies and how supermassive black holes affect the surrounding galactic neighborhood. Centaurus A, at 12 million light years away in the southern constellation Centaurus, is known as being the most prominent radio galaxy in the sky. The bright core of the galaxy emits extremely large and strong amounts of radio energy which is believed to be evidence of a supermassive black hole roughly 100 million times more massive than the Sun. Black holes often have eyes bigger than their stomachs and swallow more matter from the galaxy than they can handle and the excess matter gets blasted out millions of miles into space in massive jets of radiation, in this case, radio energy. Evidence of the jets can be seen in the upper left portion of the image where there is a thin redish filament. When imaged through red, blue, and green filters we can see the optical portion of the radio jets where there are high levels of oxygen and hydrogen and young star formation.
Since Centaurus A is an elliptical galaxy it has all the markings a good elliptical should have…a bright core and a almost uniformly distributed cloud of stars which are older and cooler than stars in spiral galaxies. However, Centaurus A is a strange one in that it has a dark band of cloud obscuring the galaxy’s core. The cloud is the same kind of cloud you would see in a typical spiral galaxy with spiral arms. These clouds are rich in the stellar building block element hydrogen which glows red within the cloud. Here stars are being formed within the clouds and this part of the galaxy is much younger than the rest of the elliptical part. This seems to be the leftover of a massive collision or interaction between the giant elliptical and a less massive spiral galaxy. The spiral picked a fight it couldn’t win and is in the process of being ripped apart by the elliptical.
Score another awesome image for the European Southern Observatory! The joint government institution is celebrating its 50th anniversary this year. Many happy returns and many more awe-inspiring and educational images to come!