The Gaia Space Observatory released its third batch of observations since its opening on Dec. 3, providing the most detailed map of the Milky Way so far, including information on the locations, distances from Earth and rates of motion of 1.8 billion objects.
Astronomers say the new map will help better understand Earth’s place in the universe. Giorgia Busso, a researcher at the Leiden Observatory in the Netherlands, said the data has “revolutionized” several areas of astrophysics, including the evolution of the Milky Way and the stars within it, and the study of nearby objects such as asteroids in our solar system.
The Gaia Observatory was launched in 2013 with the goal of creating the most detailed map of the Milky Way. Built at a cost of $1 billion, the spacecraft is located in orbit at Lagrange 2, one million miles from Earth. At that location, the gravitational forces from the Earth and the Sun are in equilibrium, and there are no celestial bodies to obscure the observatory’s view.
Gaia can observe a large number of stars at the same time, about 100,000 per minute and 850 million per day. Almost every two months, Gaia can scan the entire sky.
The researchers say this latest batch of data is an improvement in accuracy and scope over those released in 2016 and 2018. Combining the vast amount of research completed based on this data, scientists have now identified at least five characteristics of the Milky Way galaxy.
- the development of the Milky Way galaxy has undergone many thrilling mergers, annexing multiple galaxies, large and small, over tens of billions of years before evolving to this day.
- Collisions with other galaxies have contributed to the birth of stars in our galaxy.
It has been found that each time another galaxy impacts the Milky Way, it creates “ripples” between the stars, much like the effect of throwing a rock into water. These rippled regions concentrate more dust and facilitate the birth of new stars. One study mentions that the timing of one of these impacts, about 4.7 billion years ago, coincides with the birth of the Sun and the solar system.
- The spiral arms and silver disk of the Milky Way are “alive”.
Previously, scientists were not sure whether the Milky Way had two or four spiral arms. With the Gaia data, there is now clear evidence that the Milky Way has four arms. Scientists have different theories about the structure and causes of these arms, and no conclusion has been reached yet.
But at least some information can be determined from the Gaia data is that the stars in the spiral arms are not fixed, and each arm is like a “traffic jam” or bottleneck for a moving star, where the stars in front of it keep leaving and the ones behind it keep forming a long line.
In addition, the Gaia data show that the galaxy’s silver disk is also in constant flux. In addition to the forces from within the galaxy, the galaxy also faces the constraints of the surrounding orbiting galaxies, and under the combined influence of these forces, the galaxy’s disk is moving in all directions at all times.
- The Milky Way is constantly “pulling out” stellar belts from surrounding galaxies and dragging them into the Milky Way.
From the data, scientists also see that the Milky Way occasionally “rips out” bands of stars from surrounding dwarf galaxies and drags them into the Milky Way. Analysis of these alien stellar belts provides clues to the gravitational and internal mass distribution of the galaxy.
- So the Sun is “surfing”
A 2019 study found that within the interstellar medium between the Sun and other stars, there is a wavy gas cloud about 9,000 light-years long, with an undulating range of about 500 light-years.
The Sun is currently located 500 light-years away from this gas cloud and appears to be poised to ride a wave. Models constructed from the data show that the Sun actually just crossed a wave about 13 million years ago, and will continue to surf again and again in the future.
No wonder Cambridge astronomer Nicholas Walton said that the data provided by Gaia “gives us a picture of the ecology of the galaxy.
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