Precisely because we live in it and have no “outside” view, the skeleton of our Milky Way is essentially unknown to us. Now scientists have discovered, as they say, its first “bone.” Its name is “Nessie,” after the Loch Ness monster, but the only resemblance to it lies in its serpentine shape: the very long and thin structure could be something like our fibula, but as befits such a body, it is composed of… dust and gases.
Completing the skeleton
From what we can tell by looking at it from the inside and comparing what we perceive with what we see in other galaxies, our galaxy is spiral: that is, it is shaped like a helix with a bar in the center and two main arms that wrap around its disk. But here our knowledge stops and the exact arrangement of its "skeleton" escapes us.
Computer simulations of galaxy formation show that networks of fine filaments exist within the disks of spiral galaxies like our own. Such filaments – which astronomers call “bones” – have also been detected in observations between the arms of other spiral galaxies. However, until now, a similar structure had not been discovered in our own galaxy.
“This is the first time we’ve seen such a delicate part of the galactic skeleton,”said Alyssa Goodman of the Harvard-Smithsonian Center for Astrophysics, lead author of the study presented at the American Astronomical Society meeting in Long Beach, California.“This bone looks more like the fibula—the long, thin bone in your lower leg—than the tibia, the big, thick bone in your lower leg.
Clear structure
Dr. Goodman and her colleagues discovered the galactic bone while studying "Nessie," a cloud of dust and gas that was discovered in 2010 in Spitzer telescope data by James Jackson of Boston University, who named it that because it reminded him of the Loch Ness Monster.
Looking closer at the cloud, Dr. Goodman's team found that it is much farther away than Dr. Jackson's original calculations - at least two, but most likely up to eight times. Also, the radio emissions of the molecular gases show that it is not a random projection of material but a coordinated structure, a "feature", in the disk of our galaxy.
The newly discovered galactic "bone" resembles, as experts point out, a giant cosmic snake: it is 300 light-years long but its width is only 1-2 light-years. It is estimated that the mass of the material that makes it up is 100,000 times the mass of the Sun.
"It's possible that Nessie's bone is located within a spiral arm or is part of a network connecting larger spiral features," Dr. Goodman said. "We hope that we and other astronomers will find more of these features and use them to map the Milky Way's skeleton in 3D . "
