An international team of astronomers has captured the first image of a supermassive black hole at the centre of our own Milky Way galaxy.
The image, produced by a global team of scientists known as the Event Horizon Telescope (EHT) Collaboration, is the first, direct visual confirmation of the presence of this invisible object, and comes three years after the very first image of a black hole from a distant galaxy.
“For decades, we have known about a compact object that is at the heart of our galaxy that is four million times more massive than our Sun,” said Harvard University astronomer Dr Sara Issaoun.
“Today, right this moment, we have direct evidence that this object is a black hole.”
The image does not show the black hole itself – because it is completely dark – but the glowing ultra-hot plasma* and gas that encircles the phenomenon* in a bright ringlike structure.
This glowing halo* swirls around the black hole’s boundary beyond which nothing, not even light, can escape its gravitational pull*.
Dr Issaoun said that from Earth the black hole would look about the same size as a doughnut on the surface of the Moon.
EHT project scientist Geoffrey Bower, of Taiwan’s Academia Sinica, said: “These unprecedented* observations have greatly improved our understanding of what happens at the very centre of our galaxy.”
The black hole has been given the name Sagittarius A* (pronounced A-star), or Sgr A* for short, because it was detected in the direction of the constellation* Sagittarius.
Located 27,000 light years from Earth, its existence has been assumed since 1974 when an unusual radio source was detected at the centre of the galaxy.
In the 1990s, astronomers mapped the orbits of the brightest stars near the centre of the Milky Way, confirming the presence of a supermassive compact object there, work that led to the 2020 Nobel prize in Physics.
Though the presence of a black hole was thought to be the only plausible* explanation, the new image provides the first, direct visual proof.
Capturing images of such a faraway object required linking eight giant radio observatories across the planet to form a single “Earth-sized” virtual telescope called the EHT.
“The EHT can see three million times sharper than the human eye,” said German scientist Thomas Krichbaum, of the Max Planck Institute for Radio Astronomy.
“So, when you are sitting in a Munich beer garden (in Germany), for example, one could see the bubbles in a glass of beer in New York (in the US).”
The EHT gazed at Sgr A* across multiple nights for many hours in a row, a similar idea to long-exposure photography and the same process used to produce the first image of a black hole, released in 2019. That black hole is called M87* because it is in the Messier 87 galaxy.
The M87* and Sgr A* are similar, despite Sgr A* being 2000 times smaller than M87*.
“Close to the edge of these black holes, they look amazingly similar,” said Sera Markoff, co-chair of the EHT Science Council and a professor at the University of Amsterdam.
Both black holes behaved as predicted by German-born physicist Albert Einstein in his 1915 theory of General Relativity. His theory was that instead of being an invisible force that attracts objects to one another, gravity is a curving or warping* of space. The more massive an object, the more it warps the space around it.
The image of Sgr A* is the result of work by more than 300 researchers across 80 countries over a period of five years. Their research was published in The Astrophysical Journal Letters.
- plasma: an electrically charged gas
- phenomenon: something that is seen to exist or happen but which is difficult to explain
- halo: circle of light
- gravitational pull: when gravity pulls objects together
- unprecedented: never done, seen or known before
- constellation: group of stars that form a recognisable pattern
- plausible: able to be believed, seeming likely to be true
- warping: becoming bent or twisted out of shape
- What name is the global team of scientists known by?
- How many times bigger than our Sun is the Sgr A* black hole?
- Why was the black hole name Sagittarius A* or Sgr A* for short?
- What is the name of the first black hole that scientists captured an image of?
- Who came up with the theory of General Relativity?
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1. Condense it
This news story is quite long and includes a lot of detail. Rewrite the article for someone who is ‘time poor’ so that they could get the gist of the story in under 100 words.
Time: allow 25 minutes to complete this activity
Curriculum Links: English; Science
Brainstorm some possible headlines for your new shortened news story. Think about what will grab people’s attention and make them want to read it. Decide on your best one.
Time: allow 10 minutes to complete this activity
Curriculum Links: English
Wow word recycle
There are plenty of wow words (ambitious pieces of vocabulary) being used in the article. Some are in the glossary, but there might be extra ones from the article that you think are exceptional as well.
Identify all the words in the article that you think are not common words, and particularly good choices for the writer to have chosen.
Select three words you have highlighted to recycle into your own sentences.
If any of the words you identified are not in the glossary, write up your own glossary for them.