Main Question:

If scientists are able to determine the life cycle of a star, then how are they able to figure that out?

What is a star:

A star is a huge body of very hot, glowing gas. Stars produce light and energy from the process of nuclear fusion, which is the process were hydrogen atoms turn into helium. Some stars are more luminous than others, however, the most luminous stars are the hottest and the least luminous stars are the coolest. The expected life time of an average star is about 10 billion to 15 billion years.

Average stars life cycle:

Birth of a star: Stars are born in nebulas, which are giant clouds of gas and dust. They can reach from 100 to 600 light years in diameter( 587,862,537.318,360 to 3,527,175,223,910,164 miles). The nebulas get so large that they start to collapse on themselves, and that is what causes the birth of stars.

Middle life of a star: Throughout the life of a star, the star generates heat and energy through the process of nuclear fusion, which is the process were hydrogen atoms turn into helium. This process makes the core of the star denser, making at age and increases in size. After the hydrogen runs out, the core is full of helium and starts to expand and cool down, which leads to the red giant stage of a stars life. The helium atoms in the stars core then starts to fuse together, making carbon atoms and generating energy again, this makes the star very large in its size and mass. Then the outer layers of the star start to expand more and more. After the star expands, the outer layers will eventually drift into space and are no longer part of the inner core. once the star loses its outer layers, it continues to cool off and decrease in size, the once large star then shrinks to just thousands of miles in diameter.

End life of a star: Once the star changes all of its hydrogen atoms into helium, it stops fusing, and no longer produces heat or light. At this stage of the stars life, it has basically died and becomes almost invisible to the human eye.

How is this determined:

Scientists cannot determine the exact age of a star, but they can make and educated guess about the age of the star by the current stage that it is at and what model it fits best. For example, if a star is at the red giant stage, that means that the star is close to the end of its life.

Information:

• https://www.scientificamerican.com/article/how-do-we-determine-the-l/
• https://astronomyisawesome.com/galaxies/life-cycle-of-an-average-star/

Pictures:

• https://nasasearch.nasa.gov/search/images?affiliate=nasa&query=nebula