Artistic Impression of the "pigtail" molecular cloud. (Credit: Keio University / NAOJ)
www.MessageToEagle.com
Mysterious, Huge 'Pigtail' Molecular Cloud Discovered In The Galactic Center
5 September, 2012 - MessageToEagle.com - Astronomers have detected a huge, mysterious pigtail"molecular cloud a with a peculiar helical structure located in the Galactic Center, approximately 30,000 light years away from the solar system.
Giant molecular clouds in this region are orbit around the Galactic center along two closed orbits.
At the bottom of the pigtail molecular cloud, these two orbits intersect.
The research team led by Shinji Matsumura, a second year Ph. D. candidate, and Tomoharu Oka, an Associate Professor of the Department of Physics, Keio University made this discovery with the NRO 45m Telescope at Nobeyama Radio Observatory (NAOJ), National Astronomical Observatory of Japan.
The research team analyzed multiple molecular spectral lines in detail.
The researchers have revealed that the two giant molecular clouds collide with one another at exactly the bottom of the "pigtail" molecular cloud.
These findings suggest that the helical structure of the "pigtail" molecular cloud formed when the two molecular clouds with different orbits frictionally collided and the magnetic tube was twisted.
It is generally thought that helical structure of gas is associated with twisted and coiled magnetic lines.
The structure is occasionally observed in astronomical phenomena with magnetic force, such as the solar coronae or the jets related to the super-massive black hole in galactic center. The solar corona is the plasma gas covering the outermost atmosphere of the Sun, and it has an extremely high temperature of approximately one million-degrees Kelvin.
Within a 600-light-year radius from the center of the Galaxy where we live, there is a high density of stars and molecular gas that forms stars. The molecular gas becomes a dense "molecular cloud," and it is thought to move mainly along two elliptical orbits around the Galactic nucleus. These two elliptical orbit groups have a nested structure, and intersect at two points on the Galactic disc. At the intersections, both molecular clouds frequently collide. Researches so far suggest that those collisions between molecular clouds cause gas to be compressed, triggering active star formation.
Hasegawa, a member of the research team, noticed the existence of a helical molecular cloud when he carefully examined the mass data of 115-GHz rotational spectral lines emitted by carbon monoxide (CO) molecules. The 45m Telescope at Nobeyama Radio Observatory (NRO), NAOJ, acquired the data. The helical structure is approximately 60 light years by 60 light years.
Wondering what this was, Hasegawa contacted his co-researcher, Oka, about it. Oka and other team members immediately searched a similar structure in the data taken by ASTE (Atacama Submillimeter Telescope Experiment) covering the same region.
Sure enough, they also found the same helical structure in the data of 346-GHz spectral lines emitted by CO molecules.
However, the helical structure in that data was not clear. "Therefore, I proposed that we should make additional observations to confirm the existence of the molecular cloud with the helical structure, and to uncover what made this peculiar, helical-structure molecular cloud," said Oka.
After that, they started follow-up observations of the molecular cloud named "pigtail" due to its shape, using the NRO 45m Telescope.
Matsumura explained, "In order to solve the mystery of the pigtail molecular cloud, we carried out high-resolution spectroscopic observations of rotational spectral lines for six other molecules. Those molecules are clues to understanding the physical state.
"We were amazed by the clear and beautiful helical structure of the "pigtail" molecular cloud in the data taken by the follow-up observation.
The data revealed that the pigtail molecular cloud has a huge volume of gas, several hundreds of thousands times greater than the Sun has.