First picture of a black hole is one of those great, self-negating concepts, like the sound of silence, the presence of absence or the lives of the dead.
The nature of one refutes the other. But a picture of a black hole has arrived nonetheless — revealed Wednesday morning in simultaneous press conferences held in six different locations around the world.
The image reveals at the center of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This hole resides 55 million light-years from Earth and has a mass 6.5-billion times that of the Sun.
National Science Foundation
“We are delighted to report to you that we have seen what was thought to be unseeable”; said Shep Doeleman, Harvard University senior research fellow and director of the Event Horizon Telescope (EHT); at the announcement at Washington’s National Press Club.
True to the nature of the science
The picture does not show the black hole itself. The defining feature of all black holes is that they are so dense; generating a gravity field so powerful, that nothing, not even electromagnetic energy; which, of course, includes visible light — can escape their pull. What the picture reveals instead is the black hole’s so-called event horizon; the swirl of gas and dust and stars and light itself, circling the gravitational drain; before they’re sucked inside never, ever to reemerge.
In April of 2017, a global web of eight radio telescopes located in six places; (Chile, Mexico, Spain, Hawaii, Arizona and the Antarctic).
The light from the M87
“The light from the M87 black hole has to travel for 60,000 years through its own galaxy, then for 55 million years across interstellar space,” said Doeleman. “Then it had to make it through our atmosphere, where the greatest enemy of the photons is water vapor.”
The black hole at the center of our galaxy goes by the name Sagittarius A*. It has a mass equivalent to about 4.1 million of our suns. While that earns it the sobriquet “supermassive black hole”; (more common black holes can be as small as five solar masses); it’s actually something of a pipsqueak as these things go. It measures perhaps 24 million miles across, or about a 50 billionth the size of the galaxy. Trying to take an image of that from the 26,000 light year distance at which the Earth; sits from the center of the Milky Way is like trying to spot an orange on the surface of the moon; with the naked eye.
The black hole at the center of M87, by contrast, has a mass equivalent to 6.5 billion suns, or 1,585 times bigger than our own black hole. But at 2,700 times the distance, it was even harder to see.
The collection of the data was completed in barely a week; but the collation and analysis of it took the better part of the past two years. The researchers from the different observatories divided into four teams and worked independently. Sharing no information among themselves about preliminary results, lest they influence or contaminate one another’s data. Each team generated its own image of the M87 black hole from the data it had collected; and then they regrouped.
The black hole at the center of M87, meantime, is ravenous, sucking in matter and blowing out jets of supercharged particles; that approach light speed and extend for 5,000 light years. “It’s really a monster,” said astrophysicist Sera Markoff of the University of Amsterdam, another member of the EHT team. “It’s almost the size of our entire solar system, with jets that can penetrate its entire galaxy.”
The EHT is by no means finished with its black hole work.
Three new telescopes are being online—in Greenland, France and another in Arizona. And a second observing run was already conducted in April 2018.
That data is now being analyzed, too, with much more surely to come. Virtually all large galaxiesare thought to be organized around a central black hole. The known universe contains anywhere from 200 billion to 2 trillion galaxies, and while there’s a great deal of debate on the exact number. There’s no denying that the sample group is huge. We will never survey them all; we will surely survey more. And now, at last, we know how to do it.