Weekly Psalm 19: Centaurus A

Here is your weekly reminder of Psalm 19 — Centaurus A.

Colour composite image of Centaurus A, revealing the lobes and jets emanating from the active galaxy’s central black hole. This is a composite of images obtained with three instruments, operating at very different wavelengths. The 870-micron submillimetre data, from LABOCA on APEX, are shown in orange. X-ray data from the Chandra X-ray Observatory are shown in blue. Visible light data from the Wide Field Imager (WFI) on the MPG/ESO 2.2 m telescope located at La Silla, Chile, show the stars and the galaxy’s characteristic dust lane in close to

Centaurus A is an active galaxy, also known as an AGN (active galactic nucleus). This means an unusually large amount of energy is radiating from its central region (i.e. its nucleus) compared with normal, quiescent galaxies like our own Milky Way. There is strong evidence that every AGN is powered by a supermassive black hole actively feeding on gaseous material; that material becomes superheated as it spirals down and releases a huge amount of radiation. The supermassive black hole in Centaurus A is measured to be 55 million times the mass of our Sun.

An extreme case of an AGN is a quasar, which can outshine a thousand Milky Way-type galaxies. Centaurus A is a less-extreme type of AGN called a radio galaxy, which means it emits an unusually large amount of radiation in the radio part of the spectrum.

The image above is a composite image showing the galaxy in visible light, with submillimeter emission in orange and X-ray emission in blue. Submillimeter radiation falls between the infrared and microwave parts of the electromagnetic spectrum; neither submillimeter nor X-ray emission can be detected with the human eye, so this is what’s called a false-color image. If we had eyes that could detect this sort of emission, this is what the galaxy might look like to us.

Centaurus A is about 12 million light-years from Earth, appearing in the constellation Centaurus. Its brightness makes it the fifth-brightest galaxy in the sky.

Image credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)