In 5 billion years, the Sun will exhaust its hydrogen, expand into a red giant, and engulf Earth.

Question

Contrary to popular belief, the Sun will not explode in a supernova. Instead, in roughly five billion years, it will exhaust its hydrogen fuel, expand into a red giant, and likely engulf nearby planets, potentially including Earth. Following this phase, the Sun will shed its outer layers, creating a planetary nebula, while its core will become a white dwarf. This dense remnant will cool gradually, leaving behind traces that may one day be observed by distant astronomers. https://www.sciencefocus.com/space/sun-explode-ulimate-fate

Answer 1

Reading over the article, it doesn’t seem to have any evidence to back up the claim, nor is it very convincing of reliability. The article is written as a personal story in first-person, kind of like a blog post, it uses a Gety image of the sun, and mentions no quotes or sources other than a “newly published paper” that we are not given any details about. It gives the impression that it is more of a theoretical opinion piece than an actual scientific research study. However, after doing more research on the author, she seems to be a decently credible source of information. Dr. Katie Mack studied cosmology at Princeton and has been doing theoretical research on stars for most of her life. Additionally, this information can be verified because the same research is listed on the NASA website. An article from science.nasa.gov says that “When it starts to die, the Sun will expand into a red giant star, becoming so large that it will engulf Mercury and Venus, and possibly Earth as well. Scientists predict the Sun is a little less than halfway through its lifetime and will last another 5 billion years or so before it becomes a white dwarf.” This information is almost identical to the information provided in the BBC article, and possibly could have been the research paper Mack was referencing. Because it can be backed up with NASA, a highly credible source, I believe that the information provided in this article is true. Instead of a research piece, it seems to be more of a blog post in an attempt to spread and help interpret recently discovered information about the sun’s future.

Answer 2

You're absolutely correct that the Sun, in about 5 billion years, will exhaust its hydrogen fuel, expand into a red giant, and potentially engulf Earth. However, let’s clarify a few details about this complex process, which reveals that not all stars end their lives in a supernova explosion.


The Sun, like all stars, is a sphere predominantly made up of hydrogen, which fuses into helium in its core due to immense density and temperature. This process releases vast amounts of energy that counterbalance the star's gravitational pull, preventing it from collapsing. However, every star has a finite amount of fuel. When a star exhausts its hydrogen, it can no longer sustain this equilibrium and begins a transformation.

From this point, a star’s fate diverges based on its mass, following one of four primary paths to its end:

1. Stars Less Than One-Third the Mass of the Sun  – Becoming Red Dwarfs

Small stars, with masses less than one-third of the Sun’s, evolve slowly, burning their hydrogen at a remarkably steady rate. Over time spans far exceeding the current age of the universe, these stars continue to convert hydrogen in outer layers while accumulating helium in the core. They will eventually dim into faint white dwarfs without any explosive end. These enduring stars, known as red dwarfs, are expected to outlast all other types of stars.

2. Sun-Like Stars (0.3 to 8 Times the Mass of the Sun) – Becoming Red Giants then White Dwarfs  

Stars with masses similar to the Sun’s can sustain helium fusion in the core once hydrogen is exhausted. The increase in core temperature and density from this fusion pushes the star’s outer layers outward, forming a "red giant." At this stage, helium fusion releases energy more rapidly than hydrogen, causing the star’s external layers to expand dramatically. However, as helium depletes, the star contracts and heats again, allowing fusion of carbon and possibly oxygen. When fusion can no longer continue, the outer layers are ejected, forming a planetary nebula, and leaving behind a dense core—now a white dwarf—that will cool slowly over trillions of years.

3. Massive Stars (8 to 20 Times the Sun's Mass) – Ending in Type IIa Supernovae then Neutron Stars

Larger stars, with masses between 8 and 20 times that of the Sun, undergo successive fusion stages after hydrogen, producing elements like neon, oxygen, and silicon. With each stage, the energy output increases briefly until iron forms in the core. Since iron fusion does not produce energy, the core collapses under its own gravity, leading to an intense compression that generates a supernova explosion. The star’s core becomes an ultra-dense neutron star, while the outer layers explode into space, scattering heavy elements that seed future stars and planets.

4. Hypergiant Stars (More Than 20 Times the Sun's Mass) – Collapsing into Hypernovae then Black Holes  

Stars with masses exceeding 20 times that of the Sun also fuse heavier elements up to iron, but their enormous mass leads to a collapse so violent that it can bypass the neutron star stage, resulting in the direct formation of a black hole. The rapid collapse and rotation generate massive energy bursts known as gamma-ray bursts, some of the most energetic events in the universe.

Three other particular scenarios represent unique forms of stellar death, influenced by specific circumstances:

1. White Dwarfs in Binary Systems – Ending in Type Ia supernovae
A white dwarf in a binary system can accumulate gas from its companion, creating immense pressure until runaway fusion occurs, causing the white dwarf to explode in a Type Ia supernova.

2. Neutron Star Collisions – Kilonovae

In binary systems where both stars end as neutron stars, gravitational interaction brings them closer over billions of years until they collide, releasing ten times the energy of a supernova and forming a black hole.

3. Stars Torn Apart by Black Holes  –  Tidal Disruption Events

When a star approaches a black hole too closely, intense tidal forces stretch and compress the star, tearing it apart. The debris spirals into the black hole, releasing energy as it disappears beyond the event horizon.

Here is the bibliography I used for this answer:

Ho, A. (2021, July 2). Les mille et une morts des étoiles. Pourlascience.fr. Retrieved from https://www.pourlascience.fr/sd/astrophysique/les-mille-et-une-morts-des-etoiles-22000.php

Kasen, D. (2017, March 28). Des kilonovæ aux ultranovæ. Pourlascience.fr. Retrieved from https://www.pourlascience.fr/sd/astrophysique/des-kilonovae-aux-ultranovae-9577.php

Luminet, J. (2003). La mort des étoiles. Études sur la mort, 124(2), 9-20. https://doi.org/10.3917/eslm.124.0009 

Gal-Yam, A. (2012, June 21). Super-supernovae. Pourlascience.fr. Retrieved from https://www.pourlascience.fr/sd/astrophysique/super-supernovae-6817.php