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04/10/2019 – Ephemeris Extra – Event Horizon Telescope reveals the black hole in galaxy M87

April 10, 2019 Comments off

At 10 a.m. I found the live feed from the National Science Foundation presenting the results of the Event Horizon Telescope.  It was one of four simultaneous presentations around the world at that hour.  The buzz beforehand was that they would present the image of the black hole in our galaxy Sagittarius A*.  It was not.  The image presented was of the black hole in the galaxy M87, some 55 million light years away.  It turns out that The black hole in M87 is easier to image.  Our black hole appears to be too variable in brightness for this first attempt.  The M87 black hole has a mass of 6.5 billion times that of our sun.  Our black hole has a mass of about 3 million suns.  The size of a black hole’s event horizon is proportional to its mass.  So the M87 black hole is about 2,000 times larger than our black hole, but about 2,000 times farther away.  So they would appear to be the same size on the sky.

Black hole in M87

The first image of the black hole in M87. Credit Event Horizon Telescope/Katie Bouman*.

The round spot in the center is not a shadow, but the event horizon itself.  It is black because no light can escape it.  The ring around it is the accretion disc of material spiraling in to the black hole.  I believe the disc is close to perpendicular to our line of sight, but not close.  The brightest part near the bottom is material that is approaching us, while the dimmer part above is material flowing away.

There are many articles and a video of the news conference by pointing you favorite search engine to M87 black hole.

About M87:  More formally Messier 87, is a galaxy near the center of a vast cluster of galaxies about 55 million light years from us.  Charles Messier found it in 1781 while searching for comets.  He recorded it as object number 87 on his list of fuzzy objects that didn’t move and thus were not a comet.   We amateur astronomers use his Messier Catalog to view these, what we call, deep sky objects.  M87 is a giant elliptical galaxy that was also a radio source called Virgo A.

The Wikipedia article Messier 87 has already been updated to include the results presented of earlier today.

* Update:  Dr. Katherine Bouman AKA Katie Bouman lead the team that created the algorithm that processed the data from the eight radio telescopes of the Event Horizon Telescope.  Her ideas on how to perform this feat of mathematical and computer wizardry were presented in a TED Talk in 2016.