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Capturing the picture of this black gap required an Earth-sized telescope » Behind the Headlines

The Milky Means is a hazy, dare I say milky, band of sunshine seen within the evening sky. In 1610, Galileo Galilei used his telescope to point out the sunshine emanated from particular person stars. In 1920, scientists first argued that the Milky Means doesn’t include all the celebrities within the Universe however is as an alternative simply considered one of many galaxies. Quick ahead to final week, and people noticed the black gap on the middle of our galaxy for the primary time, because of developments in science and expertise and the worldwide collaboration of researchers that assist the Occasion Horizon Telescope (EHT).

In accordance with, “On Thursday, a world workforce of astronomers gave us the primary glimpse of the supermassive black gap on the middle of the Milky Means. Dubbed Sagittarius A* the gravity- and light-sucking monster some 26,000 light-years from Earth has the identical mass as 4 million Suns.”



The primary-ever picture of Sagittarius A*, the black gap on the middle of the Milky Means galaxy. Picture credit score: Occasion Horizon Telescope


Per the EHT web site, “Though we can not see the black gap itself, as a result of it’s fully darkish, glowing gasoline round it reveals a telltale signature: a darkish central area (known as a “shadow”) surrounded by a shiny ring-like construction. The brand new view captures gentle bent by the highly effective gravity of the black gap, which is 4 million instances extra large than our Solar.”

Contemplating that the black gap is 27,000 light-years away from Earth, how did the scientists from EHT seize the picture? The reply to that query lies in how the EHT collects knowledge and the way the scientists created an algorithm to show the large quantity of knowledge into the picture shared final week. The result’s the first-ever visible proof of the large object on the middle of the Milky Means.

PBS shared, “The picture is the primary visible proof of Sgr A*’s existence; the black gap was beforehand solely not directly confirmed by observations of stars in orbit round it.”

Picture credit score: NASA by way of BBC


“Till now, we didn’t have the direct image to show that this light big within the middle of our galaxy is a black gap,” Feryal Özel, an astrophysicist on the College of Arizona, stated throughout a Nationwide Science Basis information convention held on Might 12. “It reveals a shiny ring surrounding the darkness, and the telltale signal of the shadow of the black gap.”

The flashes of sunshine captured within the picture are produced when matter, similar to planets or particles, is pulled into the black gap’s outer boundary. This boundary is known as an occasion horizon.


A telescope the scale of Earth

In a fantastic analogy, the EHT workforce explains that given the gap from Earth, seeing the black gap within the sky is like recognizing a donut on the moon’s floor. EHT makes use of very-long-baseline interferometry to create the picture, with telescopes unfold throughout our globe, successfully turning our planet into an Earth-sized telescope to seize an amazing quantity of knowledge. EHT then reassembles the terabytes into the picture with an algorithm known as CHIRP (Steady Excessive-resolution Picture Reconstruction utilizing Patch priors. )

The measurements taken to assemble the picture of the black gap got here from seven radio telescopes unfold around the globe that comprise the EHT. An eighth telescope on the South Pole aided in calibrating these measurements. Every telescope can see a small a part of the black gap, and collectively, they kind a digital telescope the scale of the world that successfully works collectively like one big dish.

EHT map. Picture credit score:  D. Marrone/UofA


The observations had been carried out at a wavelength of 1.3 millimeters, which is 2000 to 3000 instances longer than the wavelength of visible gentle.

Seth Fletcher, Chief Options Editor for Scientific American, described the method: “There’s solely a really restricted time period annually when telescopes in Europe, North America, South America, Antarctica can all see the identical issues within the sky. In order that they put collectively [an] elaborate schedule of when Sagittarius A*, for instance, is gonna be up over the horizon and visual to what telescopes.

“They simply scan black holes for a number of nights. Then they take all the information in exhausting drives. Then they bodily ship it to 2 tremendous pc banks, one in Massachusetts, one in Germany, after which they correlate all of it right into a single knowledge set. After which they search it for frequent detections the place all of its telescopes have seen the identical factor.”

Instrumenting the telescopes to work collectively

So as to sew collectively the information, the EHT groups want to make sure the excessive bandwidth knowledge is collected in the identical means at every telescope.

To make sure constant knowledge assortment, every telescope requires the identical high-performance instrumentation. The EHT primarily based its instrumentation on digital {hardware} and expertise developed by the Collaboration for Astronomy Sign Processing and Electronics Analysis (CASPER).

CASPER designs and ships FPGAs boards to every telescope website to make sure the telescopes are processing the noticed radio waves in the identical means. These FPGAs had been designed with Simulink. The top-users at every website make the most of a highly-efficient polyphase filter financial institution for sign processing. A polyphase filter financial institution is just like a quick Fourier remodel (FFT), however with improved channel isolation. The FPGAs provide greater throughput and higher vitality effectivity than a typical CPU or GPU.

“Simulink was essential in producing the M87 and up to date picture of the black gap on the middle of the galaxy,” says Dan Werthimer, chief scientist on the Berkeley SETI Analysis Middle. “The Casper FPGA instrumentation ran in any respect the radio telescopes and picked up a number of petabytes of knowledge used to make these photographs. Simulink was additionally used to design and take a look at the beamformer devices that mixed alerts from all of the antennas in each Chile and Hawaii websites for these photographs.”

The picture exceeded expectations

Per the EHT weblog, the picture has superior our understanding of our personal galaxy. “We had been shocked by how nicely the scale of the ring agreed with predictions from Einstein’s Idea of Basic Relativity,” stated EHT Challenge Scientist Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei. “These unprecedented observations have enormously improved our understanding of what occurs on the very centre of our galaxy, and provide new insights on how these big black holes work together with their environment.”

The EHT workforce’s outcomes are being printed at this time in a particular problem of The Astrophysical Journal Letters.


EHT picture of the black gap, Sagittarius A*. The inset photographs symbolize totally different imaging options and their related frequency (histograms). Picture credit score: The Astrophysical Journal Letters.




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