THE LIFE CYCLE OF A LOW MASS STAR (simplified) | Astronomy

Summary

This video explores the fascinating life cycle of a low-mass star, beginning with its formation in a nebula. The star progresses from a protostar to a main-sequence star, like our Sun, where it spends most of its life. Eventually, it expands into a red giant, consuming nearby planets. As its core becomes unstable, it sheds its outer layers, forming a planetary nebula, leaving behind a white dwarf. Over billions of years, the white dwarf cools and potentially becomes a black dwarf, a theory not yet observed by scientists.

Takeaways

• 🌌 There are an estimated 300 billion stars in the Milky Way galaxy, and billions of galaxies in the universe.
• 🌟 Each star has a unique life cycle, which differs depending on whether it's a low-mass star or a high-mass star.
• 🌠 All stars start in a nebula, a cloud of gas and dust, where the process of star formation begins.
• 👶 A star in its earliest stage is called a protostar, which lasts anywhere between 10,000 and 100,000 million years depending on the star's size.
• ☀️ When hydrogen starts fusing into helium, the star becomes a main-sequence star, where it spends about 90% of its life.
• 🌞 Our Sun is currently a main-sequence star, and it will remain in this stage for about 5 billion more years.
• 🔴 Once a main-sequence star runs out of hydrogen, it becomes a red giant, which is cooler but significantly larger.
• 🔥 A red giant will eventually expand, potentially absorbing nearby planets like Mercury and Venus, and making Earth uninhabitable.
• 💫 After the red giant phase, the star sheds its outer layers, creating a planetary nebula, with a white dwarf remaining at the center.
• 🖤 Over billions of years, the white dwarf cools down and is theorized to become a black dwarf, though none have been discovered yet.

Q & A

What is the estimated number of stars in the Milky Way galaxy?

It is estimated that there are around 300 billion stars in the Milky Way galaxy.

How many galaxies are there in the universe?

There are billions of galaxies in the universe.

Where do stars begin their life cycle?

Stars begin their life cycle in a nebula, which is a cloud of gas and dust.

What is a protostar, and how long does it remain in this stage?

A protostar is a baby star that forms before hydrogen fusion begins. It remains in this stage for 10,000 to 100,000 million years, depending on its size.

What happens when a protostar begins to fuse hydrogen into helium?

When hydrogen fusion begins, the star becomes a main-sequence star, which is the stage where it spends most of its life.

What percentage of known stars are main-sequence stars?

About 90% of known stars are main-sequence stars.

What will happen to our Sun after about 5 billion years?

In about 5 billion years, our Sun will burn out of hydrogen and become a red giant, expanding and eventually making Earth uninhabitable.

What is a red giant, and why is it called that?

A red giant is a star that has expanded and cooled after using up its hydrogen fuel. It is called 'red' due to its lower temperature (around 5,000 Kelvin) compared to a main-sequence star.

What happens to a star after it becomes a red giant?

After becoming a red giant, the star sheds its outer layers, creating a planetary nebula, while its core remains as a white dwarf.

What is the final stage in the life cycle of a low-mass star?

The final stage is when the white dwarf cools and theoretically becomes a black dwarf, which no longer emits light or energy.