Black holes are points in space where gravity is so strong that nothing can escape, not even light. They are intriguing mysteries to astronomers and science-fiction fans alike. Thanks to the work of an international collaboration, we’re one step closer to better understanding exactly how black holes work. And the more we know about them, the more we can unravel about the history of our own little galaxy, the Milky Way.
While black holes were predicted by Albert Einstein’s theory of general relativity in 1915, our first images of black holes only came to be this century. In 2019, the Event Horizon Telescope (EHT) Collaboration published an image that was made from direct observations of the Messier 87 galaxy’s black hole, M 87*, made in 2017. In 2022, they released their first images of our local black hole Sagittarius A* (aka Sgr A*, which is read as Sagittarius A star). Those images were both produced by observing radio waves around the edge, or event horizon, of the black holes. However, each year brings technological advances to the EHT Collaboration. Last month, the first polarized image of our black hole was released in The Astrophysical Journal Letters, revealing a mesmerizing magnetic field that appears to spiral out.
Observing the polarized light waves of Sgr A* lets scientists chart the magnetic fields close to the black hole. This step forward unlocks new understanding of how black holes work. Astronomers happened upon a surprise because this polarized image is similar to an earlier polarized image of the M 87* black hole. Both black holes appear to have magnetic fields that are similarly organized and have comparable behaviors. This is telling, because M 87* and Sgr A* are very different black holes in term of size and surroundings. While Sgr A* is 4.3 million times as big as our Sun, M 87* is 6.5 billion times as big. This size difference is part of the reason why it was much harder to capture an image of Sgr A* despite it being only 27,000 light-years away from Earth, compared to M 87* which is 53.5 million light-years away. While particles on their edges move at similar speeds, it take exponentially longer for particles to finish whipping around M 87*. Also notable, M 87* is surrounded by more gas and dust.
Despite these differences, the similar magnetic fields suggest that all black holes are governed by the same physical processes. It also suggests that the Milky Way’s black hole contains a jet, which is a powerful outflow of energy. A jet is the most energetic mechanism in the entire universe, and its clearing out of gas and dust helps give way to stars and galaxies. Indeed, learning that Sgr A* likely has a jet alters scientists’ understanding of how the Milky Way came to be.
Of course, there is still much more to learn about our home galaxy and the universe itself. Each year, technological advances help the EHT Collaboration deepen their understanding of black holes. For the EHT Collaboration—an international consortium of astronomy programs and telescopes ranging from the Atacama desert to the South Pole—each telescope contributes to their “very long baseline interferometry.” This interferometry uses data taken from across the planet at different angles and times to create a fuller image and essentially act as an Earth-sized telescope. Each year, the Collaboration is adding telescopes and bandwidth, providing astronomers with more data. It will once again be observing Sgr A* this month.
In the decade to come, there are hopes to have multicolored views of event horizons, as well as high-fidelity footage. There is even potential to add telescopes in outer space to add to the EHT data. It is fitting that we can only understand our place in the universe by coming together as a planet. After all, even national borders cannot escape a black hole.
New images of the magnetic fields of the Milky Way’s black hole, Sagittarius A* were released by the Event Horizon Telescope Collaboration.
The image demonstrates that Sagittarius A* acts similarly to a much bigger black hole, the M87*.
Using polarized light, astronomers now have a better understanding of Sagittarius A* and our home galaxy, the Milky Way.
The Event Horizon Telescope collaboration is a worldwide effort made up of telescopes across the entire Earth.
h/t: [PetaPixel]
All Images via Event Horizon Telescope Collaboration and European Southern Observatory.
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