Turbulent Cauldron Of Starbirth In Nearby Galaxy Centaurus A
NASA's Hubble Space Telescope offers a stunning unprecedented close-up view of a turbulent firestorm of starbirth along a nearly edge-on dust disk girdling the galaxy Centaurus A. This is the nearest active galaxy to Earthonly 10 million light-years away.
[UPPER LEFT] - A ground-based telescopic view shows that the dust lane girdles the entire elliptical galaxy. This lane has long been considered the dust remnant of a smaller spiral galaxy that merged with the large elliptical galaxy. The spiral galaxy deposited its gas and dust into the elliptical galaxy, and the shock of the collision compressed interstellar gas, precipitating a flurry of star formation.
[CENTER] - The dramatic dust disk is thought to be the remnant of a smaller spiral galaxy that merged with the large elliptical galaxy. The shock of the collision compressed interstellar gas, precipitating a flurry of star formation and giving the material a fleecy pattern. Resembling looming storm clouds, dark filaments of dust mixed with cold hydrogen gas are silhouetted against the incandescent yellow-orange glow from hot gas and stars behind it. Brilliant clusters of young blue stars lie along the edge of the dark dust rift. Outside the rift the sky is filled with the soft hazy glow of the galaxy's much older resident population of red giant and red dwarf stars. The dusty disk is tilted nearly edge-on, its inclination estimated to be only 10 or 20 degrees from our line-of-sight. The dust lane has not yet had enough time since the recent merger to settle down into a flat disk. At this oblique angle, bends and warps in the dust lane cause us to see a rippled "washboard" structure.
The picture is a mosaic of two Hubble Space Telescope images taken with the Wide Field Planetary Camera 2, on Aug. 1, 1997 and Jan. 10, 1998. The approximately natural color is assembled from images taken in blue, green and red light. Details as small as seven light-years across can be resolved. The blue color is due to the light from extremely hot, newborn stars. The reddish-yellow color is due in part to hot gas, in part to older stars in the elliptical galaxy and in part to scattering of blue light by dust -- the same effect that produces brilliant orange sunsets on Earth.
[LOWER RIGHT] - Hubble's Near Infrared Camera and Multi-Object Spectrometer was used to peer past the dust to discover a tilted disk of hot gas at the galaxy's center (white bar running diagonally across image center). This 130 light-year diameter disk encircles a suspected black hole which may be one billion times the mass of our Sun. This mass is packed into a small region of space not much larger than our Solar System. The disk feeds material to presumably an inner, unresolved accretion disk that is made up of gas entrapped by the black hole. The red blobs near the disk are glowing gas clouds which have been heated up and ionized by the powerful radiation from the active nucleus.
Resolving features as small as seven light-years across, Hubble has shown astronomers that the hot gas disk is tilted in a different direction from the black hole's axis -- like a wobbly wheel around an axle. The black hole's axis is identified by the orientation of a high-speed jet of material, glowing in X-rays and radio frequencies, blasted from the black hole at 1/100th the speed of light. This gas disk presumably fueling the black hole may have formed so recently it is not yet aligned to the black hole's spin axis, or it may simply be influenced more by the galaxy's gravitational tug than by the black hole's.
The false-color NICMOS image was taken on Aug. 11, 1997 at a wavelength of 1.87 microns ("Paschen alpha"), characteristic of ionized Hydrogen.
Click here for a look at the central supermassive black hole in the X-ray part of the spectrum.