Mark Megahan
Astronomers from the Max Planck Institute for Astronomy named it “Maggie.” A single massive structure threading it’s way through a full 3,900 light-years of space, near the heart of our own galaxy. They say it’s “one of the longest known structures in the Milky Way.”
One coherent structure
The astronomers are quick to assure the scientific world that Maggie is indeed, “a coherent structure,” even though she’s 3,900 light-years long. They can tell from the data. The way they figure that out is just a bit complicated. First of all, their pet “filament” consists “almost entirely of atomic hydrogen gas.” A long time from now she could be the mother to dozens of stars.
“Analyzing the measurements suggests that the atomic gas in this lane converges locally to form molecular hydrogen.” That’s the normal Hindenburg exploding type, as opposed to the swirl of hot quarks called “atomic hydrogen.” When “compressed in large clouds, this is the material from which stars eventually form.”
They provided a handy animation to show where Maggie lives in the Milky way, marking her location with a red line. The final images are “the distribution of atomic hydrogen, with the measured velocities represented by different colors.” There’s no shortage of hydrogen in this universe and it’s “the main ingredient in the formation of stars.” It’s just hard to see with telescopes.
“That is why the recent discovery of a surprisingly long structure, a filament, of atomic hydrogen gas by an international research group led by astronomers from the Max Planck Institute for Astronomy in Heidelberg is all the more exciting.”
Part of the success in finding the elusive structure was luck. “The location of this filament has contributed to this success,” PhD student Jonas Syed explains. “We don’t yet know exactly how it got there. But the filament extends about 1600 light-years below the Milky Way plane.”
He’s proud to list his name as first author on the paper just published in the journal Astronomy & Astrophysics. Because of the way it sits, “the radiation from the hydrogen, which is at a wavelength of 21 centimeters, stands out clearly against the background, making the filament visible.”
Seeing means measuring
Once they spotted Maggie hiding in the shadows, the “observations also allowed us to determine the velocity of the hydrogen gas,” co-author Henrik Beuther notes. “This allowed us to show that the velocities along the filament barely differ.”
That’s how they can conclude with certainty, “it is indeed a coherent structure.” It’s speedometer reading of velocity “is determined mainly by the rotation of the Milky Way disk.”
According to co-author Sümeyye Suri, “With this information and a new method for analyzing data, we managed to determine the size and distance of the filament.” She hangs out at the University of Vienna. “It is about 3900 light-years long and 130 light-years wide.” It’s also around 55,000 light-years away from Earth on the other side of the galaxy.
Until now, they only knew about clouds of molecular gas with structure about 800 light-years across. The points along the line are accumulations of condensed hydrogen gas clouds, destined to become baby stars.
One of the great things about Maggie is that astronomers will be studying her closely because “exactly how the transition from atomic to molecular hydrogen happens is still largely unknown.” That, the researchers say, “makes the opportunity to study this extraordinarily long filament all the more exciting.”
Co-author Juan D. Soler was the one who found the first clue. That’s how he got the right to name it. He chose Maggie “after the longest river in his home country of Colombia, called the Río Magdalena.” She “was already recognizable in earlier evaluations of the data. But only the current study proves beyond doubt that it is a coherent structure.“
