- 4206 - MILKY WAY - shaped by dark matter? A galactic archaeology project has revealed the Milky Way’s neighboring galaxy, Andromeda, has a violent and dramatic history. Astrophysicists looked at the chemical compositions of stars in Andromeda, which is the closest large galaxy to our own. The goal was to reconstruct its past.
--------------------- 4206 - MILKY WAY - shaped by dark matter?
- Galactic
archaeology reveals Milky Way's neighbor Andromeda has a violent past.
Chemical analysis of stars in the galaxy next door has
revealed its upbringing was more chaotic than our own galaxy's.
-
- After examining
the abundance of elements in Andromeda and considering the fact this galaxy
possesses both planetary nebulae , gas and dust blown away from dying low-mass
stars, and red giant stars, the researchers concluded that it experienced dramatic and forceful
formation.
-
- Astronomers think
the creation of the Andromeda galaxy was more turbulent than the origins of the
Milky Way. They theorize that Andromeda initially experienced a burst of
intense star formation that created the galaxy's foundation, with a secondary
period of star birth happening between 2 billion and 4.5 billion years ago.
-
- Although in many
ways Andromeda is similar to our own Milky Way, it's a similarly-sized, spiral
disc galaxy, research confirms that its history is far more intense and
dramatic, with bursts of activity forming stars in abundance, and two distinct
eras of star formation.
-
- The idea is the
second starburst period was triggered when the gas-rich Andromeda collided and
merged with another galaxy, also replete with gas, in an event that astronomers
call a "wet merger." The influx of gas in such a merger acts as the
fuel to kick-start yet more star formation.
-
- Andromeda isn’t
finished clashing with other galaxies.
Andromeda experienced collisions and mergers with other galaxies in its
past, thanks to the positions and motions of its individual stars, the stars started out in another galaxy.
-
- By looking at the
chemical compositions of these stars, astronomers found two distinct signatures
in the disc components of Andromeda. One family of stars appeared to have ten
times more oxygen than iron, while the other group appeared to have similar
amounts of both elements. This bit adds a new dimension to the understanding of
this galaxy’s past, revealing more about the nature of the suggested collision
and its effect on Andromeda’s stellar population.
-
- This is a fantastic
example of how galactic archaeology can provide fresh new insights into the
history of our universe. By analyzing
the chemical abundance in different ages of stars in Andromeda, we can bring to
life its history and better understand its origins.
-
- Andromeda likely
has a history of violence and its future
looks to be equally turbulent, with our own galaxy set to become part of its
neighbor’s chaotic existence. This is because the Milky Way and Andromeda are
currently on a collision course, set to slam into each other in around 4.5
billion years. This titanic collision will give both galaxies a severe
makeover, wiping out the distinctive arms of both spiral galaxies.
-
- The stellar
population of the Milky Way and Andromeda, which is currently about 2.5 billion
light years away from us, will not slam into each other but will survive to be
thrown into new orbits around a new galactic center. Our own star, the sun, and
the entire solar system are likely to be pushed away from the new galactic
core, moving toward the outskirts of the resultant new galaxy.
-
- Oxygen is one of
the so-called alpha-elements produced by massive stars. The others are neon,
magnesium, silicon, sulfur, argon, and calcium. Oxygen and argon have been measured with
planetary nebulae, but Andromeda is so far away that the James Webb Space
Telescope (JWST) is required to measure other elements, including iron.
-
- Our entire galaxy is warping, and a gigantic
blob of dark matter could be to blame.
An invisible halo of misaligned dark matter could explain the
warps at the Milky Way's edges. The
Milky Way isn't flat; it's warped. A new study suggests an invisible halo of
dark matter could explain why.
-
- A gigantic blob
of invisible dark matter has bent our galaxy out of shape. 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: a mysterious event that knocked our
galaxy's invisible halo of dark matter out of alignment.
-
- These results, in
combination with data in the stellar halo, 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.
-
- What caused the
dark matter around our galaxy to fall out of tilt isn't clear, but 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 30, 2023 MILKY
WAY - shaped by dark matter? 4206
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