Astronomers have revised the size of the Milky Way
The two large spiral arms of the Milky Way may be about 10% further from Earth than previously thought. The new measurements indicate that the galaxy may be larger, more massive, and less symmetrical. This was reported on July 9 by the Live Science portal.
The Milky Way is a spiral galaxy with a bar. Its main structures include the arms of Sagittarius, the Centauri Shield, Perseus, and the Outer Arm. The solar system is located not in one of the four largest arms, but in a smaller branch between them.
It is difficult for scientists to determine the exact shape of the galaxy because observers are inside it and cannot see the Milky Way as a whole. Previously, the position of the outer arms was mainly calculated based on the galactic rotation rate. However, the accuracy of such estimates decreases as we move away from the galactic center.
"We usually model the outer arms of the Milky Way indirectly, using information about the rotation of the galaxy. But this approach leaves room for error," said Beatrice Vaya, lead author of the study from Italy's National Institute of Astrophysics.
For the new measurements, the astronomers used X-ray radiation from gamma—ray bursts, one of the most powerful explosions in the universe. When the light from such events passes through dense clouds of gas in spiral arms, glowing rings, or X-ray echoes, appear. The size of these rings allows you to estimate the distance to the clouds.
The researchers analyzed data from the Chandra and XMM-Newton observatories obtained after three gamma-ray bursts. Their light passed through the gas clouds in the Perseus, Shield—Centauri and Outer Arms.
Measurements have shown that the Outer Arm and the Centauri Shield arm are located about 10% further from the Earth. The difference is several thousand light years. At the same time, the distance to the Perseus arm has not changed significantly.
"The differences are small, but any revision of these distances is important because they underpin our understanding of the galaxy. This may require a change in the estimate of its mass," said Ilaria Fornasiero, a co—author of the work from the University of Bologna.
According to new data, the Milky Way may not be a regular spiral, but a more elongated and asymmetric system. For final conclusions, scientists need to measure the rest of the sleeves in a similar way. However, the approach depends on the occurrence of suitable gamma-ray bursts, so data collection may take a long time.
On June 25, Universe Today magazine reported the discovery of 16.5 million stars in the Messier 82 galaxy. According to the publication, new stars are born there 10 times faster than in the Milky Way. Scientists have linked the abnormally high rate of star formation to the collision of an object with a neighboring galaxy in the past. The astronomers also stressed that this process will not last forever: it will last for several hundred million more years by astronomical standards until the gas reserves are completely exhausted.
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