Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all
When black holes stop eating, galaxies fade away.
“I’ll never, ever be full. I’ll always be hungry. Obviously, I’m not talking about food.” –Dwayne ‘The Rock’ Johnson
Most large galaxies are illuminated by billions of stars, but some cosmic monstrosities have an even greater source of light: an active, supermassive, feeding black hole.
The active supermassive black hole at the center of galaxy Centaurus A produces two massive, bipolar jets in opposite directions. Image credit: NASA/CXC/CfA/R. Kraft et al.
They outshine all others in terms of brightness, and show unique signs over the entire electromagnetic spectrum.
The looping, swirling filaments of the galaxy at the heart of the Centaurus cluster were shocked by central emissions. Someday, they may yet be devoured by the black hole. Image credit: NASA, ESA/Hubble, A. Fabian.
Physically, the intense outburst heats up and shocks the surrounding matter as the black hole devours matter.
The galaxy NGC 1275, as imaged by Hubble, shows incredible signs of an active, feeding black hole at its center. Image credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration.
After the black hole stops feeding, some intense emission remains, even extending beyond the galaxy’s stars.
The bright emissions extending past the edge of the galaxies are evidence of prior AGN activity, but the central black holes are too dim now. Image credit: NASA / ESA / W. Keel, University of Alabama.
The orientation of an active galactic nucleus determines what we observe, but they’re fundamentally a single class of object.
For the first time, we’ve witnessed a single galaxy brighten and fade in detail: from inactive to active and back.
This galaxy in the constellation of Cetus, Markarian 1018, was viewed across the electromagnetic spectrum.
The galaxy Markarian 1018, at the center of a wide-field image from the Digitized Sky Survey. Image credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin, edits by E. Siegel.
From GALEX (UV) to the VLT (radio) and many other bands, the entire galaxy brightened in the 1980s and faded in the 2010s.
Data from Chandra and other telescopes suggest that the supermassive black hole within this galaxy is no longer being fed enough fuel to make its surroundings shine brightly. Image credit: NASA/CXC/Univ of Sydney/R.McElroy et al.
But it’s the X-rays, from Chandra, that are most revealing: dimming by a factor of 8 from 2010 to 2016.
Optical image of galaxy Markarian 1018, with an overlay of VLT (radio) data. Image credit: ESO/CARS Survey.
Starve the black hole, and your galaxy dims. An incredible cosmic lesson that we’ve now seen firsthand!
Mostly Mute Monday tells the cosmic story of a single astronomical phenomenon or object in visuals and no more than 200 words.
