File:Caldwell 77.jpg

English: Caldwell 77, also cataloged as NGC 5128 and commonly called Centaurus A, is a peculiar elliptical galaxy. Centaurus A is apparently the result of a collision between two otherwise normal galaxies, which led to a fantastic jumble of star clusters and dark, imposing dust lanes. Near the galaxy's center, leftover cosmic debris is steadily being consumed by a central supermassive black hole, making Centaurus A something astronomers call an active galaxy. As in other active galaxies, the black hole’s feeding process generates bursts of radio, X-ray and gamma-ray light.

“Only” about 11 million light-years away (not far in cosmic terms), Centaurus A is the closest active galaxy to Earth. The galaxy is about 60,000 light-years wide, but this Hubble image zooms in on a region that is about 8,500 light-years wide. The image combines observations taken in visible, infrared and ultraviolet light using Hubble’s Wide Field Camera 3 in 2010. Hubble’s observations of Centaurus A have provided insights into star formation in the galaxy, peering into regions typically obscured by dust and revealing the vibrant glow of young, blue star clusters. Using its infrared vision, Hubble also discovered that a tilted disk of hot gas 130 light-years across is encircling the black hole at the heart of Centaurus A, which is likely supplying material to a smaller, inner accretion disk that feeds the black hole. In addition, astronomers have used Hubble to probe the galaxy’s outskirts, finding that Centaurus A’s vast halo of stars extends much farther out than previously imagined.

In 1986, Centaurus A got the world’s attention when amateur astronomer Robert Evans discovered a Type Ia supernova in the bizarre galaxy. Supernovae like this one erupt after a compact star called a white dwarf siphons material off of a companion star, resulting in an uncontrolled fusion reaction that ultimately detonates the white dwarf. Since then, Centaurus A has produced just one more known supernova, observed in 2016.

Centaurus A was discovered by astronomer James Dunlop in 1826. It is the fifth brightest galaxy in the sky, making it an ideal target for amateur astronomers. It is best spotted from the Southern Hemisphere in autumn and can be found in the Centaurus constellation. Northern Hemisphere observers will need to be as far south as possible and look for the galaxy low in the southern sky during late spring. With a magnitude of 6.7, it’s visible in binoculars, but a telescope is recommended for ideal viewing. Through a telescope the galaxy will appear nearly circular, with its prominent, dark dust lane crossing the center.

For more information about Hubble’s observations of Caldwell 77, see:

hubblesite.org/contents/news-releases/2011/news-2011-18.h...

Credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: R. O’Connell (University of Virginia) and the WFC3 Scientific Oversight Committee

For Hubble's Caldwell catalog site and information on how to find these objects in the night sky, visit:

www.nasa.gov/content/goddard/hubble-s-caldwell-catalog