Astronomers reveal the first-ever picture of a black hole

On April 10, 2019, in coordinated press conferences around the world, researchers unveiled the first direct visual evidence – a photo, albeit in the “light” of radio waves – of a supermassive black hole. This is the result of a multi-year, international collaboration. The astronomers said it presents “paradigm-shifting” observations of the gargantuan black hole in the center of the galaxy M87, 55 million light-years from Earth. The image doesn’t show the black hole itself; black holes are black because no light can escape them, and thus the holes themselves are invisible. Instead, what astronomers are calling the black hole’s “shadow,” a bright ring formed as light bends in the intense gravity around the hole. This black hole, by the way, at M87’s heart, is thought to be some 6.5 billion times more massive than our sun.

To obtain the image, astronomers used the Event Horizon Telescope – a planet-scale array of eight ground-based radio telescopes – designed specifically to capture the first-ever black hole photo.

This breakthrough was announced April 10 in a series of six papers published in a special issue of The Astrophysical Journal Letters. To say it is a big deal for astronomers is an understatement. Although black holes have been studied for decades, they’ve been largely theoretical objects. All the images you’ve ever seen of them have been computer simulations or artist’s conceptions, until now.

Black holes are extraordinary cosmic objects with enormous masses but extremely compact sizes. The presence of these objects affects their environment in extreme ways, warping spacetime and super-heating any surrounding material.

Multiple calibrations and imaging methods revealed a ring-like structure with a dark central region – the black hole’s shadow – that persisted over multiple independent EHT observations.

Supermassive black holes are relatively tiny astronomical objects – which has made them impossible to directly observe until now. As a black hole’s size is proportional to its mass, the more massive a black hole, the larger the shadow. Thanks to its enormous mass and relative proximity, M87’s black hole was predicted to be one of the largest viewable from Earth – making it a perfect target for the EHT.

The shadow of a black hole is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole’s boundary – the event horizon from which the EHT takes its name – is around 2.5 times smaller than the shadow it casts and measures just under 40 billion kilometers [25 billion miles] across.

The Event Horizon Telescope links telescopes around the globe to form an Earth-sized virtual telescope. Its Earth-sized scale gives it sensitivity and resolution that’s truly unprecedented: hence, the first-ever black hole image. The EHT is the result of years of international collaboration. It offers scientists a new way to study the most extreme objects in the universe predicted by Einstein’s general relativity during the centennial year of the historic experiment that first confirmed the theory.

Breakthroughs in technology, connections between the world’s best radio observatories, and innovative algorithms all came together to open an entirely new window on black holes and the event horizon.

And, as with all new advances in science, this new step forward is sure to lead to more questions! Astronomers and astronomy enthusiasts are already asking them.