▲ Credit: NASA/McDonald Observatory A star’s life is similar to a person’s. At first, it starts as a lump of gas and gradually grows larger, and at some point, it gathers the mass necessary for the nuclear fusion reaction and starts to glow. As it gathers additional gas and grows further, it enters the main-sequence stage, which is a regular star, and shines for a long time.
However, like humans, separate aging proceeds slowly. As the hydrogen gas in the center gradually runs out and helium or heavier elements accumulate, the star grows larger. And a star with the mass of the sun eventually passes through the final old age, the red giant stage, and meets its end, leaving a white dwarf as a keepsake. On the other hand, stars more massive than the sun face a more violent end with a supernova explosion.
But what actually matters to us is the rare but supernova explosion of a massive star. This is because heavy elements are created at this time. In fact, right after the universe was created, there were only hydrogen and helium in the universe. All of the heavy elements that make up Earth and humans were created as a result of supernova explosions.
Astronomers call any element heavier than hydrogen or helium a metal. As time passes, the universe becomes rich in metals, so stars with more metals can be said to be younger stars. Therefore, the proportion of metal is also used as an important indicator when identifying regions with many young stars in a galaxy.
Ironically, however, it is harder to map young stars in our galaxy than more distant galaxies. Because we are inside the galaxy, it is difficult to see the whole from the outside like other galaxies.
However, a team led by Keith Hawkins of the University of Texas conducted research to map young stars in our galaxy to the extent possible. Using data from LAMOST and the European Space Agency’s Gaia telescope, which contain information about the chemical composition of more than 2 billion stars, the research team completed a map of the ages of stars up to 32,600 light-years from Earth.
Looking at the map, you can see that the young stars, marked in red, are mainly concentrated in the center of the galactic spiral arms. This means that a place where a lot of gas and stars gather is a place where new stars are formed. The sun, on the other hand, was slightly out of here.
The age of the sun is 4.6 billion years, so if you compare it to a human, you can now say half of your life as a star in your early 40s. Stars belonging to the MZ generation or younger are farther away, and the Sun is among the older stars. But on the other hand, because that amount of time has passed, intelligent life like humans could have evolved.
In fact, young stars, intermediate stars like the sun, and stars that supply materials to the universe at the last moment are all part of the universe and can be said to be a cycle of nature. Humans live a very short life compared to the stars, but science is exploring and understanding this process.
Gordon Jung Science Columnist jjy0501@naver.com
