First photograph of the region surrounding the black hole at the centre of galaxy M87. (Event Horizon Telescope Collaboration)
What a time April has been for astronomy and space aficionados, with a recent host of groundbreaking achievements.
SpaceX and its brash CEO Elon Musk could rightly bask in the accolades they received for the second launch of the biggest American rocket, Falcon Heavy, this time with a commercial payload. Not only was the payload delivered into orbit, but, for the first time, SpaceX successfully recovered three boosters by landing two back at the launch site and one far out at sea.
Canadian astronaut David Saint-Jacques completed a marathon space walk to upgrade components outside the International Space Station.
However, capturing media attention worldwide was a photograph that was just a hundred kilobytes or so in size. A photograph that had been many years in the making, involving teams across the world.
Ever since American physicist John Wheeler coined the expression black hole for objects from which even light couldn’t escape, there has been speculation about their existence and about their role in the universe. Einstein famously didn’t believe in these odd objects, but the work of Wheeler, Stephen Hawking, Roger Penrose, and many others established not only their existence but their ubiquity.
Penrose, who on the day the now famous photo was released was coincidentally in Vancouver addressing an overflow crowd at UBC, told The B.C. Catholic that a primary takeaway from the image was that it moved the existence of black holes from speculation and fantasy to fact.
Essentially, a photograph of a black hole is a photo of nothing. Rather than being an image of a black hole, it instead displays the silhouette of a black hole framed by the rotating material in the accretion disk around it. This material moves with incredible speeds, accounting for the apparently asymmetric appearance of the region. The brighter parts are moving towards us, the darker parts away from us.
Using equipment across the earth, the Event Horizon Telescope team, comprised of scientists and funding from multiple nations, began eight years ago to put together a strategy to capture a photograph of a black hole. Essentially, the process called for six large radio telescopes to collect highly synchronized data across a period of four days in April 2017. Although the data collection took only mere minutes each of those days, so great was the volume of data that it required the storage equivalent of 5,000 one-terabyte drives that are commonly found in home computers.
VLBI, or very long baseline interferometry, is the name of the well-established technique of combining radio telescopes together to make a virtual machine that in this case is about equal in size to the diameter of the earth. The EHT team believed that its eight radio telescopes, in six sites, would be able to resolve details of the region around a black hole and it set about imaging the one at the centre of galaxy M87. Black holes are designated with an asterisk, so in this case it was M87* that the team planned to image. At the heart of our own galaxy is black hole Sagittarius A*, which will likely be a target for a subsequent project.
This work broke new ground in image processing, taking about two years to distill the data that was collected and reduce it to the single image that enthralled many.
In an interview with the BCC about the remarkable work to photograph M87*, the Vatican’s chief astronomer, Bro. Guy Consolmagno noted that like anyone else he stands in awe of God’s remarkable universe.
As an astronomer, he said it is quite exciting because it means for the first time we can begin to see directly things happening around and perhaps even inside a black hole that we were only able to theorize about before. This first image is only a first step; future technology and future techniques hold immense promise.
Here is the statement that Bro. Consolmagno gave the Italian bishops to describe the watershed event of photographing a black hole.
“This image by the Event Horizon Telescope (EHT) consortium is the first and most direct confirmation that black holes actually exist just as predicted Einstein’s theory of General Relativity. It opens up a new way to explore nature at its most extreme. It is also a tribute to how people from many nations and cultures can collaborate in painstaking work towards a common goal. And as it happens, the chair of the science council for the EHT, Dr. Heino Falcke, is an alumnus of the 1993 Vatican Observatory Summer School!”
Dr. Falcke summarized it best via Twitter when he noted after the years of work it took his team to image M87*: “The best thing: we finally can share this precious image with the entire world – where it belongs.”
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*
The first observed black hole, by the numbers
Name: M87*
Unofficial name: Pōwehi, Hawaiian for “embellished dark source of unending creation.”
Where: Galaxy M87, discovered by Charles Messier in 1781
Distance: 55 million light-years
Diameter: greater than diameter of our solar system
Mass: 6.5 billion suns
Radio telescopes used: 8
Data processed: 5 petabytes
Hard drives to store 5 petabytes: just over 1,000
Years to process data: 2
Scientists involved: more than 200
Size comparison: Like photographing an orange on the moon from Earth