From Ethan Siegel: “What Is The Biggest Black Hole As Seen From Earth?”

From Ethan Siegel


The supermassive black hole at the core of galaxy NGC 1277 weighs in at 17 billion solar masses. But it’s too distant to be resolved from Earth. Image credit: NASA / ESA / Andrew C. Fabian / Remco C. E. van den Bosch (MPIA).

If you collapse a large enough mass into a small enough volume, you’ll create a black hole.

The anatomy of a very massive star throughout its life, culminating in a Type II Supernova. Image credit: Nicole Rager Fuller for the NSF.

Every object has a gravitational field, and without enough speed, you can’t leave it; you can’t reach escape velocity.

For black holes, where escape velocity is bigger than the speed of light at the event horizon, nothing can escape, not even light.

Black holes may still emit light from outside the event horizon, as accelerated matter either falls in or is funneled into jets, but nothing inside the event horizon can ever escape. Image credit: ESO/L. Calçada, of an illustration of the quasar SDSS J1106-1939.

Black holes are formed from the collapse of incredibly massive objects: ultramassive stars imploding in supernovae at the end of their lives.

But common, stellar mass black holes, at 1-100 times the Sun’s mass, are surpassed by rarer, supermassive ones.

The core of galaxy NGC 4261, like the core of a great many galaxies, show signs of a supermassive black hole in both infrared and X-ray observations. Image credit: NASA / Hubble and ESA.

Almost every galaxy has one, including our Milky Way.

Sag A*  NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way
Sag A* NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way

The largest flare ever observed from the supermassive black hole at our galaxy’s center. Image credit NASA/CXC/Stanford/I. Zhuravleva et al.

At 4 million solar masses, our black hole is only 26,000 light years away.

Andrea Ghez, UCLA

Other, larger, more distant galaxies, like Messier 87, have even larger black holes, reaching into the billions of solar masses.

Three views of the center of Messier 87 and its central, 6.6 billion solar mass black hole. Images credit: Top, optical, Hubble Space Telescope / NASA / Wikisky, via Wikimedia Commons user Friendlystar; lower left, radio, NRAO / Very Large Array (VLA); lower right, X-ray, NASA / Chandra X-ray telescope.

Later this decade, an array of radio telescopes — the Event Horizon Telescope — comes online.

Event Horizon Telescope Array

Event Horizon Telescope map

The locations of the radio dishes that will be part of the Event Horizon Telescope array. Image credit: Event Horizon Telescope sites, via University of Arizona at

Arizona Radio Observatory
Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

Atacama Pathfinder EXperiment (APEX)

CARMA Array no longer in service
Combined Array for Research in Millimeter-wave Astronomy (CARMA)

Atacama Submillimeter Telescope Experiment (ASTE)
Atacama Submillimeter Telescope Experiment (ASTE)

Caltech Submillimeter Observatory
Caltech Submillimeter Observatory (CSO)

IRAM NOEMA interferometer
Institut de Radioastronomie Millimetrique (IRAM) 30m

James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

Large Millimeter Telescope Alfonso Serrano
Large Millimeter Telescope Alfonso Serrano

CfA Submillimeter Array Hawaii SAO
Submillimeter Array Hawaii SAO

Future Array/Telescopes


Plateau de Bure interferometer
Plateau de Bure interferometer

South Pole Telescope SPTPOL
South Pole Telescope SPTPOL

With a resolution of 10 micro-arc-seconds (μas), it should see the Milky Way’s supermassive black hole’s event horizon.

The expected view of the Milky Way’s supermassive black hole through the Event Horizon Telescope. It should be the only one directly visible. Image credit: S. Doeleman et al., via

With an angular size of 19 μas, no other black hole appears larger from Earth.

See the full article here .

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“Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan