Core of the Milky Way seen like never before

(ORDO NEWS) — New images, taken by a radio telescope in South Africa, reveal many details in the heart of our galaxy.

The astronomer Rafael Bachiller reveals to us in this series the most spectacular phenomena of the Cosmos. Topics of exciting research, astronomical adventures and scientific news about the Universe analyzed in depth.

New images, taken by a radio telescope in South Africa, reveal a multitude of details in the heart of the Milky Way: star-forming regions, supernovae and hundreds of very long filaments of unknown origin.

core of the Milky Way seen like never before 1                                                       The galactic center region observed

Best on radio and from the South

The center of our galaxy is hidden behind large dusty clouds that stand in front of us, preventing us from seeing the innermost and most interesting areas in visible light.

However, the radio waves, which are strongly emitted from there, pass through these dust clouds as if they were transparent. Therefore, radio telescopes can be used to study these regions in whose depths a supermassive black hole lives: Sagittarius A*.

On the other hand, the central zone of the Galaxy is hardly observable from the northern hemisphere. The constellation of Sagittarius is seen much higher on the horizon from the southern hemisphere and that is why many large observatories are installed in these southern latitudes.

For these reasons, the MeerKAT radio telescope, which is made up of 64 antennas spread over an area 8 kilometers in diameter in South Africa, is a magnificent instrument for investigating the secrets of the center of our galaxy.

And it is from this observatory that some images have just been made public that are amazing due to the level of detail they contain.

1.28 Gigahertz

The new study has been coordinated by Ian Heywood, from the South African Radio Astronomy Observatory ( SARAO ) and the University of Oxford.

Of course, these are not the first images obtained of the region in radio waves, but they are by far the most detailed and the ones with the highest level of sensitivity. The images, taken at a wavelength of 1.28 GHz (gigahertz), cover an area of ​​the sky 6.5 square degrees, equivalent to 30 times that of the full moon.

It is really a mosaic of images (total 100 megapixels) that was obtained over 20 independent observations during more than 200 hours of telescope time.

In the images, the brightest area is the one closest to the supermassive black hole Sagittarius A*, which is 25,000 light-years away and contains a mass 4 million times that of the Sun. supernova remnants, the expanding shells of gas that result when high-mass stars end their lives explosively, expelling much of their material into interstellar space.

core of the Milky Way seen like never before 2                                                    Supernova remnant at the edge of Mosaic

Among these large bubbles, an almost perfectly spherical one stands out at one of the edges of the mosaic. Another very spherical remnant is called G359.1-05 which, in addition to its well-defined shape, stands out for two other very curious structures found in its vicinity: the mouse and the snake. It is thought that the mouse could be formed by a neutron star ejected at high speed in a supernova-type event.

Threads and more Threads

The snake is one of the longest bright filaments of the many that have been detected in the new images. In fact, you can count up to 1,000 of these filaments in the entire mosaic. These very long threads reach 150 light years in length and are known to be associated with intense magnetic fields.

Sometimes they are seen singly, sometimes in pairs, and often in large skeins of parallel strands kept equidistant from each other. One might think that they are structures similar to the great bows and loops that occur on the solar surface, but in the galactic center the scales are much larger.

Since the discovery of these filaments in the 1980s (the article with their discovery was published in the journal Nature ), astronomers have struggled to find a conclusive explanation for their formation. The bright radio emission must come from high-energy charged particles (cosmic rays) spinning at speeds close to the speed of light when they fall near strong magnetic field lines.

But when one tries to go into the details of this explanation, one is quite perplexed. Firstly, because it is not known where such abundant cosmic rays (the densest in the Galaxy) could come from and, secondly, because the magnetic fields must be amplified in the filaments to values ​​that are much higher than those that prevail in the rest of the surrounding interstellar medium, and it is not known what mechanisms could cause this magnetic amplification.

The new data will make it possible to make good statistics on the properties of the filaments, such as lengths, orientations, curvatures, magnetic field values, spectrum of the emitted radiation, etc. This will allow further study of their possible formation mechanisms.

Numerous star-forming regions with large clusters of massive stars and numerous compact sources can also be seen in the new images, some may be pulsars (neutron stars), others may be black holes in other galaxies far beyond our own. The researchers are now cataloging all the objects that can be identified in the image, recognizing the ones that were observed before, and reporting on all the ones seen for the first time.

Waiting for the Ska

These images of the galactic center are a taster of observations to be made by the Square Kilometer Array ( SKA ) radio telescope, which is already under construction in South Africa and Western Australia. In fact, the 64 MeerKAT antennas will be included in the South African SKA section along with another 133 new satellite dishes that will be distributed in three spiral arms spanning 150 kilometres. At the same time, more than one hundred thousand very low frequency antennas will be installed in Australia.

SKA will be the largest radio telescope in the world for centimeter waves and longer, a technological display that will require an investment of 1,900 million euros in the 2021-2030 period. Naturally, Spain, one of the world’s greatest powers in radio astronomy, has been actively involved in this project since it began more than three decades ago.

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