About 13.8 billion years ago, our Universe was born in the Big Bang “crucible,” which gave rise to the first subatomic particles and the laws of physics that have survived to the present day. About 370,000 years later, the first hydrogen atoms formed in the Universe, which, together with helium, are the nuclear fuel for stars that produce heavier elements. Despite the fact that hydrogen is still the most abundant element in the Universe, clouds of this gas in interstellar space are very difficult to detect and study, and yet they contain a lot of information about the early stages of star formation, the evolution of galaxies and the cosmos as a whole.
All of the above makes astronomers interested in finding and studying large hydrogen clusters. And recently a group from the Max Planck Institute for Astronomy, Germany, discovered the largest strand of atomic hydrogen in our galaxy, the Milky Way galaxy. The discovered structure was named “Maggie”, it is 55 thousand light-years away, practically on the other side of the galaxy, and it is one of the longest galactic structures discovered by scientists in the history of astronomy.
The Maggie filament was discovered thanks to data collected during the THOR (HI/OH/Recombination line survey of the Milky Way), which was conducted with the Very Large Array (VLA) radio telescope in New Mexico. With observations in the centimeter wave range, scientists are studying the formation of hydrogen clouds, the conversion of atomic hydrogen into molecular hydrogen, and much more related to the formation of stars, galaxies and the evolution of the cosmos as a whole.
The main goal is to investigate the processes by which dense clouds of the two most abundant hydrogen isotopes are formed. These isotopes include atomic hydrogen (H), which consists of one proton and one electron, and molecular hydrogen (H2), deuterium, whose atom consists of one proton, one neutron and one electron. As the cloud forms, the amount of molecular hydrogen in the cloud increases, and seals emerge that become the “germs” of future stars. But the processes that cause hydrogen to change from atomic to molecular form are still largely unknown today.
Compared to other known hydrogen clouds, which have an average length of 800 light-years, the Maggie cloud seems enormous, measuring 3900 light-years long and 130 light-years wide. At the same time, part of the cloud, 1600 light-years long, extends beyond the plane of our galaxy.
Detect the thread “Maggie” was only possible due to the fact that the gas it contains moves at a speed of 54 kilometers per second in the direction opposite to the direction of rotation of the galaxy. This motion is the source of radiation with a wavelength of 21 centimeters, known as the “main hydrogen line.
Analysis of the cloud’s radiation showed that it contains 8 percent molecular hydrogen. Moreover, scientists were able to find places where the gas is already beginning to accumulate and form seals, in which the processes of transition of hydrogen from atomic to molecular form will proceed more intensely.
“However, many of the existing questions still remain unanswered,” the researchers write, “And we hope that additional data we will get with the James Webb Space Telescope (JWST) and the Square Kilometer Array (SKA) radio telescope will allow us to look into the period of ‘cosmic dawn’, see the very first stars and find answers to most questions.”