The sun's lifespan still extends to approximately 10 billion years, but what happens next? A new study offers an answer.

Billions of years from now when Earth is unrecognizable and life is probably long gone, Albert Zijlstra from the University of Manchester and his team of researchers say the sun will dramatically transform into a ring of luminous, interstellar gas and dust. This is called a planetary nebula.

The study was published in the journal Nature Astronomy on Monday, May 7.

The Sun Will Form A Planetary Nebula

For years, scientists have wondered whether the sun has too low a mass to end up as a planetary nebula like 90 percent of all stars.

According to Science Daily, a team of researchers designed a new model predicting the lifespan of stars. They used the model to predict the brightness of the envelope — a ring of gas and dust ejected when a star dies — of stars with different ages and masses.

"The envelope can be as much as half the star's mass," Zijslra explains. "This reveals the star's core, which by this point in the star's life is running out of fuel, eventually turning off and before finally dying. It is only then the hot core makes the ejected envelope shine brightly for around 10,000 years — a brief period in astronomy. This is what makes the planetary nebula visible."

Many used to believe that the sun's envelope won't be visible at all due to its modest size. However, the new model of this recent study shows the stars heating up three times faster than old models, which means low mass stars could still produce a visible planetary nebula.

The sun is just big enough to form a visible planetary nebula, although it is expected to be faint.

How A Star's Mass Affects Brightness Of Nebula

The new model also solves a paradox that puzzled scientists for decades, Science News reported. Astronomers believed the brightness of a nebula depended on a star's mass with the larger stars producing brighter nebulae.

However, observations do not line up as planetary nebulae in elliptical galaxies with low-mass stars are just as bright as the nebulae in spiral galaxies with massive stars.

Christophe Morisset, an astronomer at the National Autonomous University of Mexico, tells the publication that the new model operates on the theory that when lower-mass stars expel their envelopes, the cores heat up more rapidly than scientists previously thought. This phenomenon, he says, allows the core to eject more radiation into the nebula, making it brighter.

This further explains how stars of varying mass form nebulae with roughly the same brightness.

"We found that stars with mass less than 1.1 times the mass of the sun produce fainter nebula, and stars more massive than 3 solar masses brighter nebulae, but for the rest, the predicted brightness is very close to what had been observed," Zijlstra says.