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The first-ever picture of a black hole captured by EHT. (Event Horizon Telescope Collaboration)[/caption]
Eastern Mirror Desk
Dimapur, April 10: A black hole and its shadow have been captured and released for the first time on Wednesday, April 10. It was a feat by an international network of radio telescopes called the Event Horizon Telescope (EHT).
Described as "a monster” by scientists, the black hole that is located in a distant galaxy measures 40 billion km across - three million times the size of the Earth. EHT researchers revealed the details of their finding in coordinated press conferences across the globe.
A black hole is an extremely dense object from which no light can escape. Anything that comes within a black hole’s “event horizon,” its point of no return, will be consumed, never to re-emerge, because of its unimaginably strong gravity. By its very nature, a black hole cannot be seen, but the hot disk of material that encircles it shines bright. Against a bright backdrop, a black hole appears to cast a shadow.
The stunning new image captured by EHT shows the shadow of the super massive black hole in the centre of Messier 87 (M87), an elliptical galaxy some 55 million light-years from Earth and has 6.5 billion times the mass of the Sun. Catching its shadow involved eight ground-based radio telescopes around the globe, operating together as if they were one telescope the size of our entire planet.
An article updated by Nasa stated that “to complement the EHT findings, several Nasa spacecraft were part of a large effort, coordinated by the EHT’s Multiwavelength Working Group, to observe the black hole using different wavelengths of light. As part of this effort, Nasa’s Chandra X-ray Observatory, Nuclear Spectroscopic Telescope Array (NuSTAR) and Neil Gehrels Swift Observatory space telescope missions, all attuned to different varieties of X-ray light, turned their gaze to the M87 black hole around the same time as the Event Horizon Telescope in April 2017. If EHT observed changes in the structure of the black hole’s environment, data from these missions and other telescopes could be used to help figure out what was going on.”
“This is an amazing accomplishment by the EHT team,” said Paul Hertz, director of the astrophysics division at Nasa headquarters. “Years ago, we thought we would have to build a very large space telescope to image a black hole. By getting radio telescopes around the world to work in concert like one instrument, the EHT team achieved this, decades ahead of time.”
While Nasa observations did not directly trace out the historic image, astronomers used data from Nasa’s Chandra and NuSTAR satellites to measure the X-ray brightness of M87’s jet. Scientists used this information to compare their models of the jet and disk around the black hole with the EHT observations.
There are many remaining questions about black holes that the coordinated NASA observations may help answer. Mysteries linger about why particles get such a huge energy boost around black holes, forming dramatic jets that surge away from the poles of black holes at nearly the speed of light. When material falls into the black hole, where does the energy go?
“X-rays help us connect what’s happening to the particles near the event horizon with what we can measure with our telescopes,” said Joey Neilsen, an astronomer at Villanova University in Pennsylvania.
Nasa space telescopes have previously studied a jet extending more than 1,000 light-years away from the centre of M87. The jet is made of particles travelling near the speed of light, shooting out at high energies from close to the event horizon. The EHT was designed in part to study the origin of this jet and others like it. A blob of matter in the jet called HST-1, discovered by Hubble astronomers in 1999, has undergone a mysterious cycle of brightening and dimming.
“Scheduling all of these coordinated observations was a really hard problem for both the EHT and the Chandra and NuSTAR mission planners,” Neilsen said. “They did really incredible work to get us the data that we have, and we’re exceedingly grateful.”
Neilsen and colleagues, who were part of the coordinated observations, will be working on dissecting the entire spectrum of light coming from the M87 black hole, all the way from low-energy radio waves to high-energy gamma rays. With so much data from EHT and other telescopes, scientists may have years of discoveries ahead.