discover the black hole in the middle of the Milky Way

Posted on 05/13/2022 at 6:00 p.m.

(credit: AFP)

For the first time, astronomers have managed to extract a supermassive black hole at the heart of the Milky Way. Called Sagittarius A *, this object is the equivalent of 4 million stars the size of the Sun and is 26,000 light-years from Earth. The historical picture was presented yesterday at several simultaneous press conferences. It is also detailed in six scientific studies published in the Anthrophysical Journal. According to the findings, experts believe that more space secrets can be discovered.

The international team that determined the structure of Sagittarius A * is part of the Event Horizon Telescope (EHT) project, which is made up of more than 300 scientists from 80 institutes. Three years ago, the same team managed to capture images of another supermassive black hole, M87 *, the equivalent of a mass of 6 billion stars similar to the Sun and located 55 million light-years away. Despite using the same technique, the latest discovery has created more work, as the new cosmic region is much smaller and surrounded by dust clouds.

Technically, a black hole cannot be studied directly because the object is so dense and its gravitational pull is so strong that even light cannot escape its gravitational pull. But it is possible to detect the matter circulating around it before it is swallowed. “It’s like taking a clear picture of a dog trying to catch its tail,” said Chi-Kwan Chan, a researcher at the University of Arizona (USA) and one of them. responsible for the work.

The search for unprecedented images began in 2017 and involved eight telescopes that had to work on the same tune to take advantage of the 12-minute gap, during which the gas cloud surrounding Sagittarius A * completely merges. it turns and moves away, revealing the silhouette of a black hole. Together, the devices formed an Earth-sized virtual telescope. “It was necessary for all this equipment to capture the same light wave front,” said Antxón Alberdi, a member of the Andalusian Institute of Astrophysics and a consortium of scientists in Spain.

the laws of physics

Based on the data, the researchers were able to compare the structure of M87 * and Sagittarius A * and, by some calculations, found that they behaved similarly. Scientists believe that this proves that the same principles of physics work at the heart of a system of two different sizes. “We have two completely different types of galaxies and two very different masses of black holes, but when you look at them more, they are remarkably similar,” says Sera Markoff, president of the EHT Science Council, a university astrophysicist. Amsterdam., Germany, and one of the authors of the study.

Elcio Abdalla, Professor of Physics at the University of São Paulo (USP) and coordinator of the project for the construction of BINGO, a Brazilian radio telescope, believes that the international project has achieved significant data thanks to years of research and technological advances. “Basically, these scientists used Einstein’s equations and studied the orbits of the stars around the black hole candidate. After making the calculations, they verified that they were correct. These observations could not have been made many years ago. Technology has advanced a lot, ”he says.

New discoveries

The next question to answer is what lies within the darkness of the hole. Researchers in charge of the study also hope that, as a new study, the first will be clarified: galaxies or black holes, an old question in astronomy. Abdalla believes that answers can be made to these and other mysteries in the area. “Through other observations, we should be able to draw conclusions about dark matter and energy. By knowing more about the universe, we can contemplate more details about the Earth,” he explains.

The USP specialist also points out that unraveling the mysteries of the universe is a laborious and slow task, but one that yields important results. “Of course, that will be for generations not yet born. But without the beginning, we will not get to this point. Science teaches us to share it with others and with generations that are not here either.”

decades of waiting

The existence of Sagittarius A * has been suspected since 1974, when the American Robert Brown detected an unusual radio source in the middle of the galaxy. But it was not until the 1990s that Reinhard Genzel, a German astronomer, and Andrea Ghez, a U.S. astronomer, confirmed the presence of the black hole, which earned the couple the Nobel Prize in Physics in 2020. The image revealed yesterday shows the first visual evidence of this object.

not a photo

“We have to keep in mind the difference between photography and image. This is not a picture. It is a visual representation of a set of radio data. It is not the result of visible light or an optical device. This result was created by combining several antennas in different parts of the Earth, as if they were a single colossal antenna. In fact, this cosmic element cannot be seen: it is the stellar material that emits radiation before the bright spots enter the so-called horizon of events, from which nothing else escapes the black hole. The advantage of this type of image is its high resolution. Sagittarius A * is a well-known radio source that astrophysicists are well acquainted with, but this technique allowed them to see details that the instrument never got. “

Naelton Mendes de Araújo, astronomer and professor at the Planetary Foundation (RJ) in Rio de Janeiro

Plants grow in lunar soil

The moon’s soil is fertile, U.S. scientists have shown. In a laboratory experiment, they were able to grow plants in samples of the lunar earth taken here on Earth by Apollo 11, 12, and 17 missions. Pioneering research also investigated how plants respond biologically to this unusual habitat. Details of the work were published in the journal Communications Biology.

In the experiment, the basic functions of this type of crop were fulfilled. The group planted seeds in the moon’s soil, added water and nutrients, and placed the area under the influence of light. Only 12 g of test soil was provided by NASA. Despite this difficulty, the results were positive: almost all the seeds used were sprouted. “We were amazed. These results show that the lunar soil did not interfere with the hormones and signals involved in plant germination,” says Anna-Lisa Paul, one of the authors of the study and a University of Florida researcher. a statement.

Over time, however, researchers observed differences between lunar soil and plants grown on Earth (control sample). Some plants in the first group were smaller, grew slower, or showed variations in shape. All of these physical signs indicate that they were “working” to counteract the chemical and structural composition of the Moon’s soil.

stressful place

The phenomenon was confirmed by the researchers when they studied the gene expression patterns of these plants. “At the genetic level, they were activating tools that are commonly used to deal with aggressive elements, such as salt and metals or oxidative stress. This showed us that they perceive the lunar soil environment as a stress environment,” Paul explained.

The team plans to test it on satellite. “For longer space missions in the future, we can use the Moon as a support point for astronauts. It makes sense to want to use the soil in the region to grow plants,” says Rob Ferle, the study’s author. .

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