Milky Way isn't a flat disk, it's corrugated
By Brooks Hays / Science News / March 11, 2015 at 2:38 PM
<<According to a new study by a team of international astronomers, the Milky Way's galactic disk resembles the undulating ripples seen after a pebble is tossed into a pond. In other words, it's not flat -- it's corrugated, like a steel roof.
The study, led by Heidi Jo Newberg, an astronomer at the Rensselaer Polytechnic Institute, in Troy, N.Y., is a reinterpretation of data collected as part of the Sloan Digital Sky Survey. The 2012 survey helped astronomers locate a ring of stars, existing just off the plane of the Milk Way's disk.
"In essence, what we found is that the disk of the Milky Way isn't just a disk of stars in a flat plane -- it's corrugated,
" Newberg explained in a press release. "As it radiates outward from the sun, we see at least four ripples in the disk of the Milky Way. While we can only look at part of the galaxy with this data, we assume that this pattern is going to be found throughout the disk.
Researchers say the observed oscillations match up with previous research models, including one theory that predicted the results of a dwarf galaxy or concentration of dark matter passing through the Milky Way. "If a dwarf galaxy goes through the disk, it would gravitationally pull the disk up as it comes in, and pull the disk down as it goes through, and this will set up a wave pattern that propagates outward.
" Newberg explained.>>
The Cartwheel galaxy and its neighbours.
Photo: ESA/NASA and Hubble.
The Andromeda Galaxy. Infrared image:
NASA/JPL/P. Barmby (CfA)
Fascinating, Art. The ripples in the Milky Way's disk suggests to me that the disk is undulating, like the surface of pond
, when a pebble has been thrown into it.
The Cartwheel galaxy is the poster child example of a spiral galaxy that has been transformed into a ring galaxy by being hit by something really major, likely a smaller galaxy that has plunged right through the Cartwheel's center. Fascinatingly, the Andromeda galaxy also appears to be a ring galaxy rather than a classic spiral galaxy, and the culprit that has transformed it is almost certainly its small satellite galaxy, M32
, which has probably passed right through the disk of M31 on at least one occasion.
The Milky Way is, by all accounts, not a ring galaxy but a spiral galaxy. It hasn't undergone anything like the major upheavals of the Cartwheel galaxy or the Andromeda galaxy. Yet it may well be that our galaxy has nevertheless been hit by something sufficiently substantial to make its disk undulate.
Infrared Milky Way. Photo: Coolcosmos/IPAC/Caltech.
But an image like this one certainly suggests that the Milky Way is pretty flat. Not that I know if the image was trying to show any curvature of the Milky Way.