Paris, April 6
It looks like the world will soon see the first picture of a black hole.
On Wednesday, astronomers from around the world will hold "six major press conferences" simultaneously to announce the first results of the Horizon Event Telescope (EHT), which was designed precisely for this purpose.
It was a long wait.
Of all the forces or objects in the Universe we can not see-including dark energy and dark matter-none has so frustrated human curiosity as the invisible teeth that cut and swallow stars like so many dust particles.
Astronomers began to speculate about these omnivorous "black stars" in the 1700s, and indirect evidence has since slowly accumulated.
"More than 50 years ago, scientists saw that there was something very bright in the center of our galaxy," Paul McNamara, an astrophysicist with the European Space Agency and a black hole specialist, told AFP.
"It has gravitational force strong enough to make stars orbit around it very quickly – in 20 years." To put this into perspective, our Solar System takes about 230 million years to encircle the center of the Milky Way.
Eventually, astronomers speculated that these bright spots were indeed "black holes" – a term coined by the American physicist John Archibald Wheeler in the mid-1960s – surrounded by a swirling band of incandescent gas and plasma.
On the inner edge of these luminous accretion disks, things abruptly darken.
"The event horizon" – a.k.a. the point of no return – "is not a physical barrier, you could not bear it," explained McNamara.
"If you are in that, you can not escape because you would need infinite energy. And if you're on the other side, you can – in principle. In the center, the mass of a black hole is compressed into a single point of zero size.
The distance between this so-called "singularity" and the event horizon is the radius, or half the width, of a black hole.
The EHT that collected the data for the first image was never unlike any other ever created.
"Instead of building a giant telescope – which would collapse under its own weight – we combine several observatories as if they were fragments of a giant mirror," Michael Bremer, an astronomer at the Grenoble Institute of Millimeter Radio Astronomy, told AFP.
In April 2017, eight of these radio telescopes scattered around the globe – in Hawaii, Arizona, Spain, Mexico, Chile and South Pole – were trained in two black holes in different parts of the Universe to collect data.
Studies that can be unveiled next week may boost one or the other.
Oddsmakers favor Sagittarius A *, the black hole at the center of our own elliptical galaxy that caught the attention of astronomers.
Sag A * has four million times the mass of our sun, which means that the black hole is generated is about 44 million kilometers in diameter.
This may sound like a big target, but for the set of telescopes on Earth at about 26,000 light-years (or 245 trillion kilometers), it's like trying to photograph a golf ball on the moon.
The other candidate is a monstrous black hole – 1,500 times more massive than Sag A * – in an elliptical galaxy known as M87.
It is also much more distant from Earth, but distance and size are balanced, making it easier (or harder) to identify.
One reason why this black horse might be what was revealed next week is the pollution of the Milky Way.
"We're sitting in the plain of our galaxy – you have to look through all the stars and dust to get to the center," McNamara said.
The data collected by the long-range telescope had yet to be collected and collected.
"The image algorithms we've developed fill the gaps in data we're missing to reconstruct the image of a black hole," the team said on its Web site.
Astrophysicists not involved in the project, including McNamara, are anxious – perhaps eagerly – waiting to see if the findings challenge Einstein's theory of general relativity, which has never been tested on this scale.
Innovative remarks in 2015, which yielded the scientists involved, a Nobel laureate used gravitational wave detectors to track two black holes colliding together.
As they merge, ripples in the time-space curves create a unique, detectable signature.
"Einstein's theory of general relativity says that's exactly what should happen," McNamara said.
But these were minuscule black holes-only 60 times as massive as the Sun-compared to any of them under the EHT's eye.
"Maybe the ones that are millions of times more massive are different – we still do not know." – AFP