Why is the Milky Way shaped like ripples in a pond? Scientists may have found the reason

Image: The Milky Way's long, wavy arms

Imagine that if the Milky Way is a flat, calm pool of water made up of 100 billion stars, and now someone throws a stone the size of 400 million suns into this pool, the calmness of the water surface is instantly broken. The resulting energy wave passes through the entire galactic plane, rippling the stars in the Milky Way, causing it to fall into a long-term disorder and difficult to calm down.

Astronomers suspect that something like this may have actually happened in the universe, and not just once but several times over the past billions of years.

The Royal Astronomical Society recently published the research results. The researchers explained that the Sagittarius, a Milky Way-like constellation closer to us, may have collided with the Milky Way twice, causing the stars in the Milky Way to oscillate at different speeds.

By analyzing data from NASA's Gaia spacecraft, researchers compared the speeds of more than 2 million stars in the Milky Way, especially those at the edge of the galaxy, and found a mysterious ripple, or oscillation, that seems to be squeezing the stars in the Milky Way.

"We can see that the stars are wobbling at different speeds," Paul MacMillan, an astronomer at Rhodes University in Switzerland and an author of the study, said in a translated text.

Although the researchers call this process "galactic seismology," the team has developed a model to explain the ripple effect that causes the Milky Way's stars to misalign. They believe that this ripple was also formed millions of years ago when the Sagittarius Nebula passed by the Milky Way. "This process is a bit like throwing a stone into a pond," McMillan said. Alternatively, the two galaxies may have collided even earlier, the researchers added.

Previous studies have suggested that Sagittarius may have collided with the center of the Milky Way and created the ripples. This new study shows for the first time that those ripples radiated throughout the Milky Way and affected the speed of stars. The researchers wrote in the paper that the new research results help to complete the long and violent history of the Milky Way and Sagittarius.

Currently, the mass of the Sagittarius Nebula is estimated to be 400 times that of our sun, but this is just a drop in the bucket compared to the mass of about 1.5 trillion suns in the Milky Way. Scientists speculate that the Sagittarius Nebula may have been larger in the past, but after colliding with the Milky Way, its size has dropped by about 20%.

The shape and size of the Milky Way have also changed due to this collision. A 2011 study showed that the swinging arms of the Milky Way may be the result of a collision with the Sagittarius Nebula. In addition, a 2020 study analyzed data obtained by the Gaia probe and pointed out that the collision between the Milky Way and Sagittarius caused a surge in the number of new stars in the Milky Way.

Related knowledge:

Gaia (ancient Greek mythology character) is the personification of the earth. She is the mother of all gods, the mother of Titans and giants, and the wife of Uranus. Her Roman name is "Tera". Gaia is the original mother of all gods and the ancestor of Titans, Typhon and many other children. Therefore, people also call her the mother of the earth. Gaia is also considered the source of power that keeps the earth running. Gaia and Uranus have many children.

The Milky Way Galaxy (formerly known as the Milky Way, the Tianhe, the Xinghe, the Tianhan, the Yinhan, etc.)[18] is a barred spiral galaxy that contains the Solar System[19]. Its diameter ranges from 100,000[20] to 180,000 light-years[21].

The Milky Way galaxy contains an estimated 100 to 400 billion stars[22][23] and at least this many planets[24][25]. The Solar System is located about 27,000 light-years (8.3 kpc) from the galactic center, on the inner edge of the Orion Arm, a spiraling mass of gas and dust. At the Sun's location, the orbital period is about 240 million years.[15] From Earth, the Milky Way appears as a belt around the sky, as we look from the inside of the disk. The star-forming bulge is about 10 kilometres from the core, with one or more bars radiating outward from it. The center of the galaxy is marked by a strong radio source, a supermassive black hole named Sagittarius A*. Stars and gas at large distances orbit the galactic center at about 220 kilometres per second. This constant velocity violates Kepler's dynamics, and therefore suggests that there is a large amount of mass in the Milky Way that does not radiate or absorb electromagnetic radiation. This mass is called "dark matter"[26]. It is estimated that about 95% of the universe is dark matter. The Milky Way is expected to collide with the Virgo Galaxy in 4 billion years.

The Milky Way has several satellite galaxies, all of which are members of the Local Group, as well as part of the Virgo Supercluster, which in turn is part of the Laniakea Supercluster.[27][28] The Milky Way as a whole moves at a speed of about 600 kilometers per second (372 miles per second) relative to an extragalactic reference frame. The oldest stars in the Milky Way are almost as old as the Universe itself and thus may have formed during the dark ages shortly after the Big Bang.[9]

BY:Brandon Specktor

FY: Autumn

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