View Full Version : The Milky Way in a twist

2019-Feb-06, 10:29 AM
Our Milky Way galaxy might not be flat with a bulge in the middle.


Our Milky Way galaxy's disk of stars is anything but stable and flat. Instead, it becomes increasingly 'warped' and twisted far away from the Milky Way's center, according to astronomers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC).

From a great distance, our galaxy would look like a thin disk of stars that orbit once every few hundred million years around its central region, where hundreds of billions of stars, together with a huge mass of dark matter, provide the gravitational 'glue' to hold it all together.

But the pull of gravity becomes weaker far away from the Milky Way's inner regions. In the galaxy's far outer disk, the hydrogen atoms making up most of the Milky Way's gas disk are no longer confined to a thin plane, but they give the disk an S-like warped appearance.

2019-Feb-06, 06:29 PM
This has been known for six decades.

Ken Croswell's book on the Milky Way, The Alchemy of the Heavens: Searching for Meaning in the Milky Way, even has a diagram of the warp.

From page 83:

"But the work also held a surprise. In 1956, before the final map was completed, it became apparent that the outer part of the Galaxy's disk was not flat. Rather, the region was warped like a record that had been left out in the sunlight. Some parts of the outer disk curved above the Galactic plane and others below it. Imagine the Sun within a giant clock, with the Galactic center in the direction of six o'clock. In the direction of three and four o'clock, the outer disk lies north of the Galactic plane; in the direction of nine and ten o'clock, it curves south of the plane."

from The Alchemy of the Heavens by Ken Croswell, page 83.

2019-Feb-07, 01:21 AM
You can read the (an?) original source, Kerr, F. J., Astronomical Journal, Vol. 62, p. 93-93 (1957)


Roger E. Moore
2019-Feb-07, 01:46 AM
Kerr 1957 paper is here, only one page.

http://cdsads.u-strasbg.fr/cgi-bin/nph-iarticle_query?1957AJ.....62...93K&data_type=PDF_H IGH&whole_paper=YES&type=PRINTER&filetype=.pdf