Astronomers find an Einsteinian hack to image black holes

Research of black holes has grown tremendously in the past few years. In 2015, the first gravitational waves were observed by scientists at the Laser Interferometer Gravitational-Wave Observatory (LIGO). The discovery confirmed what Einstein predicted a century ago with General Relativity and provides new insight into black hole mergers. In 2019, scientists with the Event Horizon Telescope (EHT) Collaboration shared the first image of a supermassive black hole (SMBH), located at the center of galaxy M87.

Earlier this month, the EHT announced that it had also obtained the first image of Sagittarius A*, the black hole at the center of the Milky Way. And just in time for Black Hole Week (May 2 to May 6), a pair of researchers from Columbia University announced a new and potentially easier way to study black holes. . In particular, their method could allow the study of black holes smaller than M87* in galaxies more distant than M87.

This new imaging method was developed by Zoltán Haiman (a professor of astronomy at Columbia University) and Jordy Davelaar, a theoretical astrophysicist at Columbia, the Flatiron Institute in New York, and a member of the EHT Collaboration. Their methods have been outlined in additional studies that have recently appeared in Physical assessment letter and EASY physics review. As they show in these papers, their technique combines two techniques – interferometry and gravitational lensing.

The previous technique involved using multiple instruments to capture light from distant sources, and then combine it to create a composite image. This technique allowed the EHT Collaboration to image the bright rings around M87* and Sagittarius A* (among other objects). In the latter case, the gravity of a massive object (such as a black hole or galaxy) is used to magnify and enhance the light of a more distant object.

As Haiman and Davelaar explain, when viewing a binary black hole system side by side as one passes in front of the other, astronomers should be able to use the gravity of the nearest black holes to magnify them. the bright disk of the more distant black hole. However, these observations will also reveal another interesting feature. Haiman and Davelaar say that when two black holes pass in front of each other, there is a distinctive drop in brightness that corresponds to the “shadow” of the more distant black hole.

Depending on the mass of the black holes and how tightly their orbits are entangled, these depressions can last from a few hours to a few days. The length of the dip can also be used to estimate the size and shape of the shadow formed by the event horizon of black holes, the point at which nothing can escape its gravity (even not even light). As Davelaar explained in a recent Columbia News newsletter:

“Dozens of scientists have spent years and enormous efforts creating high-resolution images of M87 black holes. That approach is only relevant for the nearest and largest black holes — the pair of holes at the center of M87 and likely our Milky Way. [W]it is our technique, you measure the brightness of black holes over time, you don’t need to resolve each object in space. This signal can be found in many galaxies”.

In gravitational lensing, the gravity of a large object is used to bend, brighten, and distort the light of other objects behind it. Image supplier: NASA / ESA / L. Calcada

As Haiman added, the shadow of a black hole is its most mysterious and informative feature. “That black spot tells us about the size of the black hole, the shape of space-time around it, and how matter falls into the black hole near its horizon,” he said. Haiman and Davelaar became interested in the phenomenon after Haiman and a team of colleagues discovered a pair of suspected supermassive black holes (“Spikey”) in 2020 at the center of a galaxy that existed during the period. the beginning of the Universe.

Discovery happens when the team is examining data from Kepler space telescope to track distant stars for small dips in luminosity, used to confirm the presence of exoplanets. Instead, Kepler The data show signs that the flare effect is caused by a pair of transition black holes that are visible next to each other. This nickname is due to the spike in brightness caused by the suspected lensing effect of black holes as they pass in front of each other.

To learn more about flare, Haiman enlisted the help of his postdoc (Davelaar) to build a model for the flare effect. While the model confirmed the spike, it also revealed a periodic decrease in brightness that they could not explain. After eliminating the possibility that this was due to an error in the model, they determined that the signal was real and began looking for a physical mechanism that could explain it. Finally, they found that each dip closely corresponds to the time the black holes make the transition relative to the observer.

The discovery of this shadow could have huge implications for astrophysicists as well as for quantum physicists. Astrophysicists have been searching for these shadows as part of an ongoing effort to test General Relativity under the most extreme conditions and environments. These experiments could lead to a new understanding of how gravity and quantum forces interact, allowing physicists to finally work out how the four fundamental forces of nature – electricity and electricity. magnetism, the weak nuclear force, the strong nuclear force, and gravity.

For decades, scientists have understood how three of the forces that govern all matter-energy interactions work. While general relativity describes how gravity (the weakest of the four) acts on its own, all attempts to explain it in quantum terms have failed. As a result, a theory of “quantum gravity,” or The Theory of Everything (ToE), has ruled out even the greatest scientific minds. This includes Einstein and Stephen Hawking, who have spent the better part of their scientific careers figuring out one of those things.

Meanwhile, Haiman and Davelaar are currently looking for other telescope data to confirm Kepler observe and verify that “Spikey” is indeed containing a pair of merging black holes. If and when their technique is confirmed, it could potentially be applied to about 150 pairs of SMBH consolidation that have been observed but are still awaiting confirmation. In the coming years, the next-generation telescope will be brought online, which will allow for more opportunities to test the technique.

Examples include the Vera C. Rubin Observatory, a large telescope in Chile slated to open later this year. Once operational, Rubin will conduct the 10-year Heritage Survey of Space and Time (LSST), which includes observations of more than 100 million SMBH. By 2030, NASA’s Laser Interferometer Space Antenna, a space-based gravitational wave detector, will also be online and provide even more opportunities to study merging black holes. With so many candidates available to study, scientists don’t have to wait too long for a breakthrough.

“Even if only a small fraction of these black hole binaries had the right conditions to measure our proposed effect, we could find many indents in this black hole,” said Davelaar. .

Read more: Columbia News

This article was originally published on Universe today via Matt Williams. Read the original text here. Astronomers find an Einsteinian hack to image black holes

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