THE LIFE CYCLE OF A LOW MASS STAR (simplified) | Astronomy
Summary
TLDRThis 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
- đ There are an estimated 300 billion stars in the Milky Way galaxy, and billions of galaxies in the universe.
- đ Each star has a unique life cycle, which differs depending on whether it's a low-mass star or a high-mass star.
- đ All stars start in a nebula, a cloud of gas and dust, where the process of star formation begins.
- đ¶ 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.
- âïž When hydrogen starts fusing into helium, the star becomes a main-sequence star, where it spends about 90% of its life.
- đ Our Sun is currently a main-sequence star, and it will remain in this stage for about 5 billion more years.
- đŽ Once a main-sequence star runs out of hydrogen, it becomes a red giant, which is cooler but significantly larger.
- đ„ A red giant will eventually expand, potentially absorbing nearby planets like Mercury and Venus, and making Earth uninhabitable.
- đ« After the red giant phase, the star sheds its outer layers, creating a planetary nebula, with a white dwarf remaining at the center.
- đ€ 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.
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