Astronomers Capture First-Ever Image of a Black Hole: Start Of A New Era In Astrophysics

first picture of black hole

For the first time in the history of mankind, scientists have captured a picture of a Super Massive Black Hole. It was achieved by the Event Horizon Telescope. The image reveals the black hole at the center of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5 billion times that of the Sun.

What Is a Black Hole:

A black hole is anything but empty space. Rather, it is a great amount of matter packed into a very small area – think of a star ten times more massive than the Sun squeezed into a sphere approximately the diameter of New York City. The result is a strong gravitational field that nothing, not even light, can escape.

Primordial black holes are thought to have formed in the early universe, soon after the big bang. Stellar black holes form when the center of a very massive star collapses in upon itself. This collapse also causes a supernova, or an exploding star, that blasts part of the star into space. Scientists think supermassive black holes formed simultaneously as the galaxy they are in. The size of the supermassive black hole is related to the size and mass of the galaxy it is in.

You can read more about Black Hole here.

M87’s supermassive black hole
M87’s supermassive black hole as seen from Hubble telescope. Source: HUBBLE HERITAGE TEAM (AURA/STScI), NASA

Predictions Of Black Hole:

The idea of a body so massive that even light could not escape was briefly proposed by astronomical pioneer and English clergyman John Michell in a letter published in November 1784. Michell’s simplistic calculations assumed that such a body might have the same density as the Sun. They concluded that such a body would form when a star’s diameter exceeds the Sun’s by a factor of 500 and the surface escape velocity exceeds the usual speed of light. Michell correctly noted that such supermassive but non-radiating bodies might be detectable through their gravitational effects on nearby visible bodies. In 1915, Albert Einstein developed his theory of general relativity. Later scientists deducted the idea of the Black Hole from his field theory.

first black hole infographic
Black Hole Anatomy. Source: EHT

What is Event Horizon Telescope?

The Event Horizon Telescope is not a traditional telescope. It is a group of eight telescopes located across five continents. The aim is to observe the immediate environment of the supermassive black hole Sagittarius A* at the center of the Milky Way, as well as the even larger black hole in the center of the supergiant elliptical galaxy Messier 87, with angular resolution comparable to the black hole’s event horizon.

But why do we need that big telescope? Well, to actually resolve details on the scale of the event horizon, radio astronomers calculated that they would need a telescope the size of Earth because its resolution is proportional to its size. As we can’t make a telescope about the size of the Earth; so scientists used a technique called very-long-baseline interferometry. Where multiple telescopes are located far apart from one another and pointed at the same object simultaneously. Effectively, the telescopes work like shards of one big dish.

Submillimeter Array (SMA) one of the event horizon's observatories
Submillimeter Array (SMA), one of the EHT observatories

Why This Event Is So Special:

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. The EHT project has two main goals, to image an event horizon for the first time and to help determine if Einstein’s theory of general relativity needs any revisions.

General relativity has held up incredibly well over the century since its introduction, passing every test scientists have thrown at it. But the EHT’s observations provide another trial in an extreme realm where predictions may not match reality. That’s because astronomers can calculate an event horizon’s expected size and shape using general relativity. These new results will also help scientists to know better about the black hole. It can clarify whether a black hole is spinning or not.

How This Project Become A Reality:

In 2009, a network of four observatories in Arizona, California, and Hawaii got the first look at the base of one of the plasma jets spewing from the center of M87’s black hole. But the small telescopes didn’t have the capability to capture the black hole itself. So the EHT (Event Horizon Telescope) recruited new observatories. In 2017 there were eight observatories across five continents.

The success of the project hinged on clear skies on several continents and exquisite coordination between the eight far-flung teams. Observations at the different sites were coordinated using atomic clocks, called hydrogen masers, accurate to within one second every 100 million years. And, on one night in April 2017, everything came together. “We got super lucky; the weather was perfect,” said Ziri Younsi, a member of the EHT collaboration based at University College London.

Each telescope collected 64 Gigabits/second of data. The raw data, which ran into petabytes, were collected on hard disks and traveled by air, sea, and land to be compiled at the Max Planck Institute for Radio Astronomy in Germany and the Massachusetts Institute of Technology’s Haystack Observatory.

The EHT ran another observing campaign in 2018 — the analysis of those data is still in the works — but canceled a planned observation campaign this year because of security issues near one of its most important sites, the 50-meter LMT Large Millimeter Telescope in Puebla, Mexico. They plan to continue to do observations once a year starting in 2020.

Full Announcement. Courtesy: Channel 4 News


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