How Long Do Stars Live?

Introduction

The lifespans of stars, those luminous beacons in the night sky, can vary widely based on their mass. The duration of a star's life depends on the amount of fuel it contains and the rate at which it burns through this fuel. This article will delve into the lifespans of various types of stars, examining examples and their overall lifetimes from formation to end.

If you want to find out more details about the life of a star and what happens in each stage of its life cycle, check out our other article, Life Cycle of a Star.

Massive Stars

Massive stars, much larger than our Sun, burn their hydrogen fuel quickly and have short lifespans of a few million years. Their immense size and high temperatures cause rapid fuel exhaustion. As they age, they expand into supergiants and end in supernova explosions, creating heavy elements in the universe.

Rigel

In the constellation Orion, Rigel is a blue supergiant star about 860 light-years from Earth. It is the brightest star in Orion and the seventh-brightest in the night sky. Rigel A, the primary star in a multiple-star system, is about 70 times larger in diameter and emits over 120,000 times more light than the Sun.

With 17 times the Sun's mass, Rigel burns its fuel quickly, giving it a main-sequence lifespan of around 10 million years. After this phase, it will become a red supergiant for a few hundred thousand years before ending in a supernova, making its total lifespan about 10.1 million years. This supernova will likely leave behind a neutron star or black hole.

Betelgeuse

Betelgeuse, located in the constellation Orion, is a red supergiant star about 700 light-years from Earth. It is one of the brightest stars in the night sky and a key feature of Orion, marking one of the hunter's shoulders. Betelgeuse is approximately 1,400 times larger in diameter than the Sun, making it an enormous and luminous star.

Betelgeuse has about 17 times the mass of the Sun, and just like Rigel, it burns its fuel quickly. Its main-sequence lifespan was around 10 million years. Now in its red supergiant phase, Betelgeuse will continue to shine for a few hundred thousand years before it ends its life in a supernova explosion. Betelgeuse's total lifespan will be roughly 10.1 million years.

Universe Size Comparison | 3d Animation Comparison | Stars Real Scale Comparison, Source: https://www.youtube.com/watch?v=5zlcWdTs2-s

Eta Carinae

Eta Carinae, located in the Carina constellation, is one of the most massive and luminous stars known. It is about 7,500 light-years from Earth and is part of a complex star system, with the primary star, Eta Carinae A, having around 100 times the mass of the Sun. Eta Carinae is best known for its incredible brightness and the Great Eruption it experienced in the 19th century, which briefly made it one of the brightest stars in the sky.

Eta Carinae A is a blue supergiant star that will have a much shorter lifespan compared to less massive stars. Its main-sequence phase lasts only about 3 million years due to the immense amount of energy it radiates, and it will spend a few hundred thousand years as a supergiant before exploding, giving it a total lifespan of approximately 3.1 million years.

Eta Carinae is currently in a highly unstable phase. Scientists expect it to end its life in a supernova or even a hypernova explosion within the next million years.

NASA Hubble Space Telescope image captures a massive pair of billowing gas and dust clouds surrounding the supermassive star Eta Carinae.

Average Stars

Stars like our Sun, which have moderate masses, have lifespans in the billions of years. These stars spend most of their lives in a stable phase known as the main sequence, steadily fusing hydrogen into helium. Their long lifespans allow them to provide a consistent energy source over extended periods, supporting the development of planetary systems and, potentially, life.

The Sun

The Sun is an average-sized star with a diameter of about 1.39 million kilometers (864,000 miles) which is about 109 times wider than Earth and a mass roughly 330,000 times that of Earth.

Our best-known star, the Sun, is located at the center of our solar system and is a G-type main-sequence star about 4.6 billion years old. With a total main-sequence lifespan of around 10 billion years, it is currently in the middle of its life and will continue shining for another 5 billion years.

It will then spend around 1 billion years as a red giant before shedding its outer layers and forming a white dwarf, which will cool for billions of years. The total lifespan, including the white dwarf phase, is estimated to be around 12 billion years.

Alpha Centauri A

The closest star system to Earth is the Alpha Centauri system, which is about 4.37 light-years away. It consists of three stars: Alpha Centauri A, Alpha Centauri B, and Proxima Centauri, and is located in the constellation Centaurus.

Alpha Centauri A is very similar to the Sun. It has a main-sequence lifespan of around 10 billion years and is currently in the middle of this stable phase. Following this period, astronomers estimate that Alpha Centauri A will evolve similarly to the Sun, with a total lifespan of around 12 billion years.

Capella Aa

Capella Aa, located in the constellation Auriga about 42 light-years from Earth, is a red giant star in a multiple-star system. It shows what the Sun might look like in the future. Capella Aa had a main-sequence lifespan of around 10 billion years. Now, as a red giant, it will stay in this phase for a few hundred million years.

Afterward, Capella Aa will transition into a white dwarf like all previously mentioned average stars and remain in this phase for billions of years as the white dwarf cools and fades. Astronomers expect the total lifespan of Capella Aa also to be around 12 billion years.

Small Stars

Low-mass stars burn their hydrogen fuel very slowly and have incredibly long lifespans. These stars, such as red dwarfs, can last for tens to hundreds of billions, or even trillions, of years. Due to their efficient fuel use and lower energy output, low-mass stars are the longest-living stars of all. Their prolonged lifespans make them stable and enduring objects in the cosmos.

Proxima Centauri

The closest known small star to the Sun, Proxima Centauri, is a red dwarf located about 4.24 light-years away in the constellation Centaurus. It has a mass of about one-eighth that of the Sun and a main-sequence lifespan of up to 4 trillion years.

Unlike larger stars, Proxima Centauri will not become a red giant. Instead, it will gradually cool and fade over trillions of years. Astronomers estimate its total lifespan will be around 4-5 trillion years.

Barnard's Star

Barnard's Star, another red dwarf, is about six light-years away in the constellation Ophiuchus. Its main-sequence lifespan is about 10 trillion years, making it one of the longest-living stars in the universe.

Barnard's Star is smaller and cooler than the Sun, with about 14% of the Sun's mass and a much lower luminosity. Similar to other red dwarfs, Barnard's Star will not transform into a red giant. Instead, it will slowly cool and fade over time. The total lifespan of Barnard's Star is approximately 10-12 trillion years.

Barnard's Star is too dim for us to see it with the naked eye despite its proximity. Still, it is well-known for its high proper motion, meaning it moves quickly across the sky relative to other stars.

Barnard's Star, showing position every five years from 1985–2005.

Gliese 581

Gliese 581, a red dwarf star located about 20.3 light-years away in the constellation Libra, has a main-sequence lifespan of around 10 trillion years. As it approaches the end of this long phase, Gliese 581 will transition into a red giant, expanding and cooling significantly.

Even though this star belongs in the small star category, it has significantly more mass than previously mentioned Proxima Centauri or Barnard's Star, so it will eventually have enough pressure and temperature in its core to become a red giant and not meet the same end as other small stars.

After the red giant phase, Gliese 581 will shed its outer layers, and its core will collapse into a white dwarf.

Gliese 581's total lifespan, from its formation to its final white dwarf phase, will be around 10-12 trillion years.

Conclusion

1. A star's mass is the one that primarily determines its lifespan, with larger stars having shorter lifespans due to their quicker consumption of hydrogen fuel compared to smaller stars.
2. Massive stars, like Rigel, Betelgeuse, and Eta Carinae, have short, intense lives lasting about 10-11 million years.
3. Stars with a mass similar to our Sun, like Alpha Centauri A and Capella, have lifespans of around 12 billion years.
4. Low-mass stars, such as Proxima Centauri, Barnard's Star, and Gliese 581, have incredibly long lifespans stretching for tens of trillions of years.

References

1. Sackmann, I. -J.; Boothroyd, A. I.; Kraemer, K. E. (1993). "Our Sun. III. Present and Future." The Astrophysical Journal. 418.
2. Prialnik, Dina (2000). An Introduction to the Theory of Stellar Structure and Evolution. Cambridge University Press.
3. Ryan, Sean G.; Norton, Andrew J. (2010). Stellar Evolution and Nucleosynthesis. Cambridge University Press.
4. Wikipedia - "Stellar evolution"