- 4200 - MILKY WAY GALAXY - is not a flat disk as we thought. We normally thing of our Milky Way Galaxy as a flat disk. Almost like a phonograph record with a bulge in the middle. But our galaxy disk appears to be warped and wavy. If our entire galaxy is warping a gigantic blob of dark matter could be to blame.
------- 4200 - MILKY WAY GALAXY - is not a flat disk as we thought.
- An invisible halo
of misaligned dark matter could explain the warps at the Milky Way's
edges. Scientists initially believed
that the Milky Way was a flat disk dominated by two spiral arms trailing stars
from a central bar, but measurements taken since the mid-20th century reveal
that it's bent inexplicably out of shape.
-
- The warping occurs
mostly at our galaxy's borders, where some regions bend downward while others
flare upward giving it the look of a crushed sombrero. Now, computer
simulations may have revealed the cause to be a mysterious event that knocked
our galaxy's invisible halo of dark matter out of alignment.
-
- These computer
results provide compelling evidence that our Galaxy is embedded in a tilted
dark matter halo. Dark matter is a
mysterious and somewhat contradictory type of matter. It makes up 85% of the
universe's matter; but because it doesn't directly interact with light, it is
completely invisible.
-
- However,
scientists can observe its gravitational effects on its surroundings. Dark
matter makes its presence known by accelerating stars to otherwise inexplicable
speeds as they orbit galactic centers; warping distant starlight; and by giving
shape to the Milky Way's galactic halo.
-
- The galactic halo
is a vast sphere of stars floating like leaves on a dark matter pond. It rests just beyond the spiral arms of the
Milky Way. Astronomers investigated this
region using the European Space Agency's Gaia spacecraft, which maps the
positions and movements of the Milky Way's roughly 2 billion stars. By poring
through Gaia's data, they discovered that the stars suspended in the galactic
halo were strangely off-kilter.
-
- A computer
model recreated a young Milky Way-like
galaxy with a dark matter halo tilted 25 degrees with respect to its disk.
After simulating the galaxy over 5 billion years, the researchers found that
they had created a very similar galaxy to our own.
-
- A dark halo tilted
in the same direction as the stellar halo can induce a warp and flare in the
Galactic disk at the same amplitude and orientation as the data. What caused the dark matter around our galaxy
to fall out of tilt isn't clear.
-
- The researchers'
simulations suggest it is likely to have been a gigantic collision, likely from
another galaxy flying into our own. This
collision could have caused the dark matter halo to tilt up by as much as 50
degrees before slowly swinging down to its current 20-degree angle elevation.
-
-
October 27, 2023 MILKY
WAY GALAXY - is
not a flat disk? 4200
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