When insurance companies evaluate fault in a vehicle collision, they base their decision on: accident investigator. These process limited data, such as the final location of the vehicle and damage on or around the vehicle. But using physics and computer models, researchers can estimate the speed, direction, and impact forces involved in a collision. Therefore, from a snapshot of the present, it is possible to decipher the history of a car accident, leading to the unique final arrangement of the vehicle and debris.
Astronomers trying to decipher the history of our home galaxy, the Milky Way, have essentially the same job and method. Except when astronomers start investigating, they have to deal with about 100 billion “cars”, all of which are still moving, and they are not 100% sure whether a collision occurred. An international team of astronomers recently undertook a mission to reconstruct the history of the Milky Way, starting with two leads. First, its shape is barred spiral galaxy. Secondly, it is 100 million years younger than the 14 billion year old universe.
A galaxy shaped like the Milky Way located 65 million light years (four 20 zeros after miles or six 20 zeros after kilometers) from Earth. Since we are inside the Milky Way, we cannot photograph the Milky Way from the front. “Barred spiral galaxy NGC 1300” by NASA Hubble Licensed to CC BY 2.0.
Astronomers analyzed data from 10 million red giant stars observed by satellites. Gaia mission telescope This is to ensure that the stars are all similar and bright enough to obtain a representative sample across the galaxy. The team used a coordinate system called , to determine where the stars are located. galactic coordinatesand their distance from earth. We also calculated how fast it was moving and in what direction. Similar to a car crash, scientists used this information to “rewind the star” to see where it came from.
Astronomers also needed to know the chemical properties of stars. In particular, they focused on the amount of substances that were not hydrogen or helium in them. metallicand the amount of material formed by helium fusion. alpha process elements. because Not all elements were formed in the big banga highly metallic star that formed in a time and place after elements other than hydrogen and helium were abundant. Similarly, stars with more alpha process elements are more evolved in their life cycles than stars with fewer alpha process elements.
The astronomers compiled these data star by star and used simulation software called . TNG50 They tested 61 different scenarios for how galaxies formed. Once they discovered a particular set of events that produced an output that most closely matched the actual data, they condensed the results into a three-phase history of the galaxy, with each phase corresponding to a defining event.
They suggested that the first stage consisted of galaxies, called galaxies, before their distinct disk shape was formed. primordial galaxy (13.6 billion to 11 billion years ago). At the time, stars appeared and moved randomly, with the researchers describing the period as “chaotic and disorderly.” The ancient stars formed at this stage are still moving chaotically, but are concentrated near the center of the Milky Way.
At the end of the protogalactic stage, gravity pulls all the stars in the disk together, rotate faster It revolved around the center of the galaxy until it reached the second stage. hot disk step (11 billion to 8 billion years ago). At that time, the galaxy's iconic flat spiral disk shape was formed. Stars emerged in periodic bursts at higher average velocities than today, i.e. more than 1.6 solar masses per year. Additionally, astronomers interpreted the metallicity mismatch between stars during their hot disk stage as evidence for the Milky Way. merge with another small galaxy.
They suggested that we are now in the third phase of galactic history, defined by stars orbiting in orderly circles. Metal-rich stars orbit toward the galaxy's resource-rich center, while metal-poor stars orbit toward the galaxy's sparse edge. they went through this stage cold disk phase Because the defining event (from 8 billion years ago to the present) was a reduction, or “cooling down”, of how stars orbited chaotically around the center of the galaxy.
Astronomers have concluded that they can reconstruct the entire structure of the Milky Way with simple images. But they also noted that improving the study will require data from more stars and the exact ages of those stars, rather than the indirect age indicators they used.
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Source: sciworthy.com
