Long ago, people believed the earth was the center of the universe. They thought the sun, moon, and stars all revolved around it. Later, they learned that the earth orbits around the sun. Nowadays, we know the sun is just a regular star in our galaxy called the Milky Way. The Milky Way has many stars – billions! – and it rotates around its center.
The sun revolves around the galaxy’s center, but it’s not smooth. Astronomers found that it goes up and down and doesn’t rotate smoothly like Earth around the sun.
Humans can’t leave the solar system. So, some question how they track the sun’s movement in the galaxy. But, there are many ways to achieve this.
We can use “Sagittarius A*” – the supermassive black hole at the center of the Milky Way – as an example. It is a radio source that can be accurately positioned. To figure out how fast the sun moves around the center of Milky Way and its location on the galactic disk, we can measure it from “Sagittarius A*”.
To explain further, let’s consider stellar parallax and motion. Stellar parallax is the small shift in star position caused by Earth’s orbit around the sun. We can measure this change to determine where stars are located and how far away they are in space.
Stellar motion means stars moving relative to us and changing their position over time. By measuring this change, we can infer the sun’s movement in the Milky Way.
We can use gas and dust found in the Milky Way. There is a lot of gas and dust in the Milky Way. They emit or absorb waves, forming spectral lines. We can calculate distance by measuring lines. To know where the sun is, we see how its lines move.
There are various methods to measure the sun’s movement in the Milky Way. Astronomers discovered the sun moves around the Milky Way center in a specific way. It moves up and down every 32 million years, covering about 250 light years. They used different methods to find this out.
(Note: The galactic plane refers to the disk-shaped plane formed by the main mass of the Milky Way)
Astronomers say that the Milky Way’s uneven gravity causes this. The Milky Way’s mass isn’t evenly spread out, so it has dense and less dense parts. When the sun moves around the Milky Way, it goes through different density areas. These have different strength and direction of gravity. So, the sun moves up and down in a wave pattern as it orbits the galaxy.
When the sun goes through the dense galactic plane, it may face more gravity. This could cause small space objects to change their path and hit the earth. In the past, this has led to extinction events for species on earth.
It is an unconfirmed guess that the sun passes through the galactic plane. Astronomers think it happened 3 million years ago. The sun moves up and down in the Milky Way every 32 million years. This means the next time it passes the galactic plane will be in 29 million years. In short, if this view is true, humans have enough time to handle it later. So, there’s no need to worry about it now.