Astronomers Make 'Rare' Observations of Dying Star, Giving Us Glimpse Into Fate of Our Sun

Astronomers have made what they describe as "rare" observations of an aging star in the process of dying—providing us with a fascinating glimpse into the eventual fate of our own sun.

The star, known as T Ursae Minoris (T UMi), is a red giant—a hugely inflated type of star in a late phase of its lifecycle—located around 3,000 light-years from Earth in the Ursa Minor constellation. In just a few billion years, our sun will likely become a red giant like T Umi, expanding to the point where the inner planets will be consumed.

"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," Meridith Joyce, lead author of a study from The Australian National University, said in a statement.

According to authors of the study—which was published in The Astrophysical Journal—the 1.2 billion-year-old star has been experiencing a series of pulses in its death throes, during which its size, brightness and temperature have varied hugely.

"Energy production in T UMi has become unstable. During this phase, nuclear fusion flares up deep inside, causing 'hiccups' that we call thermal pulses," Joyce said. "These pulses cause drastic, rapid changes in the size and brightness of the star, which are detectable over centuries. The pulses of old stars like T UMi also enrich the entire Universe with elements including carbon, nitrogen, tin and lead."

Over the past three decades, the team has been observing these pulses, giving a rare glimpse into the aging process of a star.

"We believe the star is entering one of its last remaining pulses, and we'd expect to see it expanding again in our lifetimes," Joyce said. "This has been one of the rare opportunities when the signs of aging could be directly observed in a star over human timescales."

Within the next few hundred thousand years, the authors estimate that T UMi will eventually become a white dwarf—the (relatively) small, incredibly dense remnants of stars which have shed their outer layers, spent most of their hydrogen and helium fuel, and are gradually cooling as they reach the end of their lives.

They say that the latest observations support the hypothesis that our sun will eventually turn into a red giant before shedding its outer layers, leaving behind a white dwarf about five billion years from now.

"It will become much bigger as it approaches death—eating Venus, Mercury and possibly the Earth in the process—before shrinking to become a white dwarf," Joyce said.

"Both amateur and professional astronomers will continue to observe the evolution of the star in the coming decades, which will provide a direct test of our predictions within the next 30 to 50 years," she said.

Dying star
Artist's illustration of a dying star. ESA/Hubble