The stunning black hole photo: What you're seeing

Scientists have been using a global network of telescopes in an attempt to capture the first-ever photos of a black hole.

Posted: Apr 10, 2019 7:38 PM


Of all of the crazy sounding things in the pantheon of modern physics, it's hard to beat a black hole. Generally speaking, black holes are the burned-out hulks of long dead stars, with a strong enough gravitational field that not even light can escape them.

The gravity near a black hole is so strong that it warps the very fabric of space and time. Black holes sound more like science fiction than fact, but there has been considerable indirect evidence that they exist. They are accepted by the scientific community in spite of an embarrassing admission: nobody has ever directly seen one. Well, until now.

Scientists have announced the first direct observation of a black hole at the center of a galaxy named M87. M87 is a supergiant elliptical galaxy in the constellation Virgo. It is one of the largest galaxies in the nearby universe. (Where "nearby" is the staggering distance of 53 million light years. Astronomers really do think big.)

Now a little bit of care is necessary to understand exactly what was done. Black holes are, well, black. By definition, they do not emit any light. So, the black hole was not observed directly. However, black holes are also surrounded by ordinary matter that is caught in the hole's gravitational grip.

This matter, which is typically just gas of the same type that makes up our sun, orbits the black hole at very high speeds. All of that fast-moving gas gets heated up to the point where it glows and emits all sorts of forms of electromagnetic radiation, from heat to light to radio waves. Intervening gas blocks the visible heat and light, so astronomers look for the radio waves.

You'd think that astronomers would announce that they detected this halo of radio waves surrounding the hole, and that is part of the story. However, it's more complicated than that. Because of the very strong gravity near the black hole, some of the light and radio waves are captured by it and don't escape. The result is that a black hole looks like a ring of light, with a shadow in the middle. Essentially, from a distance, the picture astronomers released of the M87 black hole looks like a coffee ring left on a piece of paper, albeit a colored one.

Since the astronomers used radio waves to see the black hole, the colors aren't what you would see with your eye. But they do have meaning. What we are seeing is the gas surrounding the black hole. One side is bright and one is dim because the black hole is spinning. The yellow shows the side of the black hole spinning toward us and the reddish side is spinning away.

Aside from the difficulties associated with seeing something that is perfectly black, another difficulty is their size. Ordinary black holes, which have a mass the few times as big as our Sun, are only about as big as the city of Chicago. Combined with their great distances, they are simply too small to see with modern technology. Seeing the closest known black hole is as difficult as a telescope in New York City seeing a single molecule in Los Angeles. This is well beyond current technical capabilities.

Luckily, the center of nearly all galaxies contain an enormous black hole. For example, the one in the center of our Milky Way galaxy has the mass of about 4 million times that of our sun with a radius about 30 times that of the sun.

However, the black hole at the center of M87 is truly gigantic. Its mass is about 7 billion times the mass of our sun. And its dimensions are huge as black holes go. It is a sphere with a radius about 130 times that of the Earth's orbit or about three times bigger than the average orbit of Pluto.

That sounds large, but the distance to M87 is so huge that the black hole at the center of that galaxy subtends a tiny angle. It is unbelievably small -- it's equivalent to the width of a line drawn by a sharpened pencil seen from the distance separating New York and Los Angeles, a task that is possible if scientists use an incredibly clever technique that uses the entire Earth as a telescope. And, luckily, the shadow cast by the black hole is about 2.5 times wider than the hole itself.

In 2006, an international consortium of astronomers formed a group called the Event Horizon Telescope. The name is misleading, as their equipment isn't a telescope in the way we ordinarily think of it. Instead, the equipment they use is called a radio telescope, which is just an ultra-sensitive radio antenna.

And another level of confusion is that the group didn't employ a single antenna. Instead what they did was to tie together a web of radio telescopes spread across the entire planet. The reason they did that is simple. How small an object a telescope can see depends crucially on the size of the telescope. The bigger the telescope, the smaller objects it can resolve.

A world-class radio telescope is only a few hundred feet across. However, by tying together a worldwide network of radio receivers, astronomers can effectively make a telescope the size of the Earth -- essentially a radio telescope about 8,000 miles wide. And by using ultra-precise atomic clocks to synchronize the observations made from around the world, astronomers were able to resolve the shadow of the black hole at the center of the M87galaxy.

Science is all about pushing the limits -- studying what was once impossible to do. And, being perfectly black, tiny and very distant, black holes certainly qualify. Yet black holes are a key laboratory for testing Einstein's theory of relativity, which is our best theory of gravity. Because of this, scientists have indirectly studied them for decades, from observing their effect on nearby stars, to seeing how they heat up giant clouds of gas, to detecting how their motion sends ripples through space and time.

But seeing one directly is a new thing and a huge advance in our ability to understand the behavior of matter under the strongest gravitational forces imaginable. And it's important to note that this work wouldn't be possible without generous support from taxpayers and science funding agencies across the world, including the National Science Foundation here in the United States. (Disclosure: Fermilab colleagues of mine are collaborators on this project and are funded by the US Department of Energy Office of Science.)

We should all take a bit of pride in our individual role in making possible this breathtaking scientific observation. In the next weeks and months, we're sure to learn even more.

Terre Haute
Cloudy
64° wxIcon
Hi: 90° Lo: 65°
Feels Like: 64°
Robinson
Cloudy
60° wxIcon
Hi: 88° Lo: 63°
Feels Like: 60°
Indianapolis
Partly Cloudy
68° wxIcon
Hi: 89° Lo: 67°
Feels Like: 68°
Rockville
Clear
63° wxIcon
Hi: 89° Lo: 65°
Feels Like: 63°
Casey
Partly Cloudy
66° wxIcon
Hi: 88° Lo: 66°
Feels Like: 66°
Brazil
Cloudy
64° wxIcon
Hi: 89° Lo: 65°
Feels Like: 64°
Marshall
Partly Cloudy
64° wxIcon
Hi: 89° Lo: 64°
Feels Like: 64°
Mostly clear, calm evening.
WTHI Planner
WTHI Temps
WTHI Radar

Latest Video

Image

Saturday Evening Forecast

Image

Saturday: Mostly sunny, unseasonably warm. High: 89°

Image

Casey-Westfield

Image

Parke Heritage football

Image

Sullivan football

Image

Robinson football

Image

VL Football

Image

North Knox football

Image

THN Football

Image

THS Football

WTHI Events

 

Illinois Coronavirus Cases

(Widget updates once daily at 7 p.m. CT)

Cases: 1590342

Reported Deaths: 26979
CountyCasesDeaths
Cook60937610925
DuPage1031521352
Will865801083
Lake764741056
Kane65399842
Winnebago38682543
Madison37731569
St. Clair34758561
McHenry32773313
Peoria25738361
Champaign25601182
Sangamon24263266
McLean21611205
Tazewell19559326
Rock Island17631342
Kankakee16523233
Kendall15274105
LaSalle14349275
Macon14248233
Vermilion12908182
Adams12589147
DeKalb11542127
Williamson11206156
Whiteside7813176
Boone756681
Jackson756683
Coles7175112
Ogle705385
Grundy693181
Clinton676498
Franklin669694
Knox6528163
Marion6454135
Macoupin636597
Henry610272
Jefferson5981131
Effingham588980
Livingston564394
Woodford549791
Stephenson540089
Randolph522996
Monroe503299
Christian481980
Morgan479995
Fulton479069
Logan473573
Montgomery462876
Lee454956
Bureau423087
Perry411171
Saline399263
Iroquois391171
Fayette387756
McDonough352155
Jersey319753
Douglas303336
Shelby300343
Crawford298930
Lawrence294631
Union293846
Wayne267957
White261530
Richland256852
Hancock253434
Pike252256
Cass247728
Clark244138
Bond242224
Clay233347
Ford233056
Edgar229844
Carroll223937
Warren220456
Moultrie209331
Johnson208922
Washington204927
Jo Daviess203525
Greene199339
Mason196251
Wabash196115
Massac195144
De Witt192730
Piatt188814
Mercer187035
Cumberland174123
Menard155812
Jasper149518
Marshall133721
Hamilton127221
Brown10138
Pulaski97311
Schuyler9608
Edwards94815
Stark76027
Gallatin7285
Scott6895
Alexander66411
Calhoun6382
Henderson63114
Hardin55713
Putnam5414
Pope4725
Unassigned1582432
Out of IL80

Indiana Coronavirus Cases

(Widget updates once daily at 8 p.m. ET)

Cases: 926604

Reported Deaths: 15083
CountyCasesDeaths
Marion1262201958
Lake626901087
Allen52772747
Hamilton43283445
St. Joseph41475584
Elkhart33129488
Vanderburgh29927439
Tippecanoe26589247
Johnson23267415
Hendricks21902340
Porter21473341
Clark17150224
Madison17065379
Vigo15815273
Monroe14298190
LaPorte14108237
Delaware13771219
Howard13635262
Kosciusko11232134
Hancock10637160
Warrick10523176
Bartholomew10341167
Floyd10200202
Wayne9690218
Grant8939196
Morgan8734158
Boone8299109
Dubois7596123
Henry7469128
Dearborn745187
Noble7294101
Marshall7237128
Cass7097117
Lawrence6862150
Shelby6457107
Jackson643981
Gibson6036106
Harrison595585
Huntington591891
Montgomery5706102
DeKalb563591
Knox537599
Miami531983
Clinton527164
Putnam525367
Whitley516251
Steuben486367
Wabash477492
Jasper471961
Jefferson461991
Ripley444175
Adams439365
Daviess4064106
Scott394963
White386257
Clay382356
Greene380189
Wells379683
Decatur379595
Fayette367176
Posey354941
Jennings346356
Washington325847
LaGrange315774
Spencer313034
Fountain309753
Randolph305487
Sullivan299447
Owen279161
Starke272761
Orange272659
Fulton268851
Jay250634
Perry247451
Carroll241127
Franklin233637
Vermillion229750
Rush228930
Parke215220
Tipton206754
Pike202538
Blackford165634
Pulaski158751
Crawford142818
Newton140742
Benton139816
Brown132646
Martin126916
Switzerland123510
Warren113416
Union93511
Ohio77211
Unassigned0468