A team of astronomers led by researchers at the Max Planck Institute for Astronomy (MPIA) has discovered one of the longest known structures in the Milky Way. It stretches for about 3900 light years and is composed almost entirely of atomic hydrogen. This filamentary structure, known as "Maggie," may represent a link in the stellar material cycle. Analysis of the measurements showed that these atomic gases converged locally to form molecular hydrogen. When compressed in large clouds, this is the material for star formation.
Hydrogen is the most extensive matter in the universe and is a major component of star formation. Unfortunately, detecting individual clouds of hydrogen is a daunting task, which makes the study of the early stages of star formation challenging. That's why this recent international team of researchers, led by astronomers at MPIA, discovered this filamentous structure excitingly.
Jonas Syed, a PHD student at MPIA and lead author of the paper published Tuesday in the journal Astronomy and Astrophysics, said: "This 'filament' location contributed to this success. We don't yet know exactly how it got there. But this 'filament' extends about 1600 light-years below the plane of the Milky Way. Thus, the radiation from the hydrogen, with a wavelength of 21 centimeters, stands out distinctly in the background, making the 'filament' visible. ”
Henrik Beuther explains: "These observations also allow us to determine the speed of hydrogen. "He is the co-author of the study and the leader of MPIA's THOR (Milky Way HI/OH/Coincident Line Survey) observation project, and this data is based on this." This allows us to show that there is little difference in speed along the filament. As a result, the researchers concluded that it was indeed a coherent structure.
Its average velocity is largely determined by the rotation of the Milky Way disk. Sümeyye Suri said: "With this information and new methods of analyzing data, we have successfully determined the size and distance of the filament". She is another co-author and former MPIA astronomer and now works at the University of Vienna. "It's about 3900 light-years long and 130 light-years wide." At a distance of about 55,000 light-years, it is located at the far end of the Milky Way. In contrast, the largest known clouds of molecular gas typically "only" stretch for about 800 light-years.
Hydrogen appears in various states in the universe. Astronomers have found that it exists in the form of atoms and molecules, in which two atoms are connected together. Only molecular gas condenses into relatively compact clouds, which develop cold regions and eventually new stars. But exactly how the transition from atomic hydrogen to molecular hydrogen happens is largely unknown. This makes the opportunity to study this particularly long "filament" all the more exciting.
Co-author Juan D. Soler had already discovered the first clue to the object a year ago. He named the filament-like structure "Maggie" after the Río Magdalena, the longest river in his native Colombia. "Maggie can already be identified in early data assessments. But only current research proves beyond a doubt that it is a coherent structure," explains Soler, who recently transferred from MPIA to the National Institute of Astrophysics (INAF) in Rome.
Upon closer inspection, the team noticed that the gases were converging at certain points along the "filament." They concluded that hydrogen gas accumulated in these places and condensed into large clouds. The researchers also suspect that those are environments in which atomic gases gradually transform into molecular forms.
- In previously published data, they did find evidence that Maggie contained molecular hydrogen with a mass fraction of about 8 percent. What we're seeing could be a region in the Milky Way where direct raw materials for new stars are being produced. As a result, new stars may form here in the distant future. "However, many questions remain unanswered," Syed noted. "The additional data, which we hope to give us more clues about the molecular gas part, is already waiting to be analyzed."