The historical image of the Milky Way’s central black hole is just the beginning

Last week, a landmark scientific achievement was released to the public: the first real photo of the Sagittarius A* supermassive black hole, which is located at the heart of the Milky Way, was taken.

The first real image ever taken of a Sagittarius black hole has been revealed. Photo: European Southern Observatory (ESO)

Now, the Event Horizon Telescope (EHT) is ready to take its next steps in observing black holes, creating videos that can show gases streaming violently in these mysterious regions of spacetime.

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Black holes are constantly spinning as gas orbits around them, in the so-called event horizon. However, motion pictures capable of showing all this disturbance have not been recorded.

Movies made with repeated images of black holes over months and years are a dream come true for the astronomical scientific community. The researchers hope that such films will show the evolution of accretion disks as gas flows around them and how magnetic fields within the disk become entangled and terminate as black holes drag them.

According to Katie Bowman, a computer scientist at the California Institute of Technology (Caltech), there have already been attempts to make a movie. “We tested this using data from 2017. We developed algorithms that allowed us to make movies and applied that to the data.” “We saw that while something was interesting, the data we currently have isn’t enough to make anything really confident.”

So scientists need more data before the video becomes viable. However, capturing this data takes a lot of time, and the telescopes that make up the EHT project have other observing programs to complete.

Agile observation could allow moving images of black holes to be captured

According to the site space.comTo meet the challenge, engineers on the team are implementing technical improvements so that by 2024 astronomers can change observations employment And on. This ability will allow scientists to take advantage of free time in telescopes for an extended period, rather than a one- or two-week observation campaign.

Vincent Fish, an astrophysicist at the Massachusetts Institute of Technology’s Haystack Observatory, describes this approach as agile observation. “You make your remarks, and then [os telescópios] He said during the US National Science Foundation (NSF) press conference last Thursday.

While these clever observations won’t begin until 2024, EHT scientists will need some time to process the data on film using the imaging techniques Bowman described.

And the first “movie star” among black holes will be Messier 87 (or M87 *), which has a mass 7 billion times the mass of the Sun and is located 54 million light-years from Earth, in the heart of the galaxy cluster. Virgo.

Comparisons of images of the Sagittarius A* and M87* black holes. credit: space.com

Despite its large dimension, this black hole appears in the sky with a size similar to that of Sagittarius A*, due to the fact that it is much larger. The gas ring depicted around Sagittarius A* could fit within the orbit of Mercury, which has a radius of about 58 million kilometers, while the M87* black hole could easily extend into the orbits of all the planets in the Solar System.

Because Sagittarius A* is so much smaller, the changes happen faster as the gas orbits the black hole—too fast for intermittent observations by the EHT to track.

In the case of the M87*, it is so large that changes to its gas ring take weeks or months to become apparent, allowing film to be shot at a greater rate.

Agile observation has other advantages. Occasionally, black holes experience an explosion as they shred an asteroid or a cloud of gas that got too close.

Observing such eruptions requires rapid follow-up, which the EHT has not been able to do so far, given the logistics of organizing the telescope schedule and preparing the necessary equipment. With quick monitoring, the EHT will be able to track the flick of a key if astronomers detect an explosion on M87* or even Sagittarius A*.

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The EHT aims to make A* polarized images.

Although we don’t have a Sagittarius A* movie any time soon, there’s a lot to look for out there in the meantime. The EHT has already measured the level of polarization in the light of the M87* gas disk, which tells astronomers about the strength and direction of magnetic fields enveloping the disk, likely emanating from the black hole itself. And this must also be done in the black hole of our galaxy.

“Our next step will be to make polarized images of Sagittarius A*, so we can see the magnetic fields near the black hole and see how they are being pulled along. [ao redor] of the black hole itself, said Michael Johnson, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, during a National Science Foundation video conference.

The EHT works by very long fundamental interferometry, a technology that combines telescopes. The distance between the telescopes, which scientists call the “baseline,” is equivalent to the aperture of an ordinary telescope.

While seven observatories collaborated to image the black hole of M87*, with the addition of the South Pole Telescope, eight observatories participated in capturing the image of Sagittarius A*.

On Twitter, the EHT team reported that eight telescopes were in use at the time the image of the M87 black hole was captured*

If more telescopes can join the EHT project, the base lines connecting the observatories could increase in number and length. Extending baselines increases accuracy, allowing scientists to see finer details.

In addition, increasing the number of baselines increases the sensitivity of EHT as well as the number of its viewing angles. This is a factor displayed in the image of Sagittarius A*, which appears jagged: the bright spots are not hot spots, but rather specific areas where viewing angles from more pairs of telescopes coincide, resulting in a stronger signal.

Three new telescopes have been added to the EHT since the M87* and Sagittarius A* images were taken: the Greenland Telescope Project (GTP) in Greenland, the IRAM NOEMA Observatory in the French Alps, and the 12-meter Kitt Peak Telescope, in the US state of Arizona.

Since GTP is located in the far north, it can only observe the M87* black hole, not Sagittarius A*. On the other hand, the South Pole telescope is unable to see M87*. Therefore, using only 10 telescopes, it will be possible to observe each of these black holes. “Adding new stations would help a lot,” said Ryan Hickox, an astrophysicist at Dartmouth College.

And other black holes in other galaxies? Unfortunately, for now, we may have to be satisfied with just two black holes. “One of the challenges is that no black hole has a large enough event horizon, as expected in the sky, that it can be easily captured with the event horizon telescope,” Hickox said.

This does not mean that the EHT cannot notice them. The network has already observed jets from some active galaxies, such as Quasar 3C273, which is 2.4 billion light-years from Earth and has a central black hole of about 880 million solar masses.

These planes can be surprisingly useful, according to Hickox. “There’s a lot of really interesting structures in these jets that tell us about how the particles accelerate around the black hole, how they interact with the environment after they’re ejected, how magnetic fields work, the composition of these particles, all of those things that affect how these jets affect the gas. on very large scales around their galaxy.”

There are still many doubts about black holes. Does it spin, and if so, at what speed? Where do your magnetic fields come from? Do they consume gas in sudden doses or in homeopathic doses? How does it affect their immediate environment in their galaxies?

With the A* Arch image version, and the ability to take motion pictures, the answers to some of these questions may be nearly within easy reach.

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