Gaze Upon A Black Hole Up Close For The Very First Time

January 05, 2020

By Jeanette Rueb

The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. In coordinated press conferences across the globe, EHT researchers revealed that they succeeded, unveiling the first direct visual evidence of the supermassive black hole in the centre of Messier 87 and its shadow. The shadow of a black hole seen here 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 km across. While this may sound large, this ring is only about 40 microarcseconds across — equivalent to measuring the length of a credit card on the surface of the Moon. Although the telescopes making up the EHT are not physically connected, they are able to synchronize their recorded data with atomic clocks — hydrogen masers — which precisely time their observations. These observations were collected at a wavelength of 1.3 mm during a 2017 global campaign. Each telescope of the EHT produced enormous amounts of data – roughly 350 terabytes per day – which was stored on high-performance helium-filled hard drives. These data were flown to highly specialised supercomputers — known as correlators — at the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory to be combined. They were then painstakingly converted into an image using novel computational tools developed by the collaboration. — Event Horizon Telescope (EHT)

(Updated 4/10/2019)

The photograph astronomers and casual stargazers have been anticipating has arrived.

Black holes are notoriously difficult to study. We’ve known about them since 1958 and theorized about their existence since 1916, but as of yet, we’ve been unable to observe them directly. Based on the laws of physics and their effects on gravity, we know they’re there, and finally, scientists may have gotten their first glimpse at the event horizon of a black hole.

The Point Of No Return

Born from dying stars, black holes are all around us. They live at the centers of galaxies and in the space where luminous, fiery bodies once stood. They teeter precariously on the edge of physics as we know it, their accretion disks spinning rapidly around a core so dense, its gravitational pull prevents light from escaping, shrouding it in darkness. Occasionally, if a black hole is located near another star, we get the rare opportunity to see that accretion disk light up as the gravity well of the black hole draws in matter from the star’s atmosphere. In most cases, these monstrous cosmic phenomena are nearly impossible to observe in the visible spectrum. The only hint we have to their existence is through the bending of light as it passes by the “hole” formed in the fabric of space-time by the immense pull of the singularity at the center of the black hole. This gravitational lensing distorts the stars behind the event horizon, leaving us with a warped view of the universe beyond.

The majority of black holes we’ve been able to study have been viewed by X-ray telescopes. As matter is pulled in toward the event horizon, colloquially referred to as the point of no return, it heats up to about 10 million degrees Celsius. At temperatures near 2,000 times as hot as the surface of our sun, the accreting matter begins to give off low-level X-ray radiation. Specialized telescopes, such as the Chandra X-Ray Observatory, record this radiation and track its movements, allowing astronomers to observe the unobservable. Now, using cutting-edge technology and a brand new approach, astronomers may have finally made headway toward peering into a black hole. At the beginning of April 2019, the Event Horizon Telescope team promised big news to come on April 10.

Peering Into The Void

The Event Horizon Telescope Project is different from any other telescope used to study black holes. Instead of a single viewer, the EHT Project uses an array of telescopes across the world to create a virtual viewer that’s roughly the diameter of the planet. The project links together radio antennae in Europe, South, Central, and North Americas, and Antarctica via very-long-baseline interferometry. With this technique, data is gathered simultaneously from all points in the “telescope” and processed to form a single image. The EHT Project has been gathering data since 2006 and based on news of the project’s previous studies, the April 10 news break could give us a glimpse into the center of our own galaxy.

At the heart of the Milky Way lies the supermassive black hole, Sagittarius A. Since the project’s inception, the global network of telescopes has been gathering data on the universe around us. Back in 2017, the project team announced that they would be releasing an image of Sagittarius A. Due to a delay caused by the winter closure of the South Pole Telescope, the data wasn’t received until the very end of the year. There has been no public release date for this first photo until now. While there’s no promise that what we’ll get on April 10 will be an exclusive peek into the heart of our own galaxy, but chances are good that it’ll be part of the package. What we do know is that we’re in for a first-ever closeup view of a black hole, and it will be a pivotal moment in astronomical history.