Nuclear fusion ‘hiccups’ on dying star offer glimpse of our own sun’s death

26 Jul 2019

Both T UMi and the sun will eventually become white dwarf stars. Image: © hallowedland/

Astronomers have managed to see a rare cosmic event that will offer us an important glimpse of how our own sun will eventually die.

An international team of astronomers has glimpsed the future – or at least the likely future – of the sun. In a study published to The Astrophysical Journal, the team documented the first ever glimpse of the death of a dying red giant star called T Ursae Minoris (T UMi).

This is an important discovery as the star shares many characteristics with our own sun, and so far what the team has seen has reinforced our predictions of how it will eventually die.

“This has been one of the rare opportunities when the signs of ageing could be directly observed in a star over human timescales,” said Dr Meredith Joyce, who is based at the Australian National University and was co-lead of the study.

“We anticipate our sun and T UMi will end their lives much more quietly and slowly compared with a supernova – a powerful and luminous explosion.”

When the sun eventually dies, likely to be 5bn years from now, it will turn into a red giant and then into an expanding and glowing ring-shaped shell of gas. During this expansion, the Earth, Venus and Mercury will all be swallowed up with the remaining gravestone being a small white dwarf.

Nuclear fusion ‘hiccups’

T UMi is approximately 1.2bn years old, has a mass roughly twice that of the sun and is located in the Little Bear constellation found more than 3,000 light years away. Prior to transitioning to a white dwarf, the star has been undergoing a series of pulses whereby its size, brightness and temperature have fluctuated drastically.

This has left the star unstable, with the nuclear fusion reaction within flaring up deep inside, resulting in ‘hiccups’ referred to as thermal pulses.

“These pulses cause drastic, rapid changes in the size and brightness of the star, which are detectable over centuries,” Joyce said. “The pulses of old stars like T UMi also enrich the entire universe with elements including carbon, nitrogen, tin and lead.”

In its current state, the star is believed to be entering its final pulses and will likely expand in size within our lifetime. It will become a white dwarf within the next few hundred thousand years. In the meantime, astronomers will continue to monitor the star over the next few decades to test further predictions about the death of the sun.

Colm Gorey was a senior journalist with Silicon Republic