In about 10 billion years’ time, our sun will die. But scientists have been unable to predict with confidence exactly what will happen next.
Ninety percent of all stars end their lives as so-called planetary nebulas—vast, spherical clouds of bright (luminous) gas and dust. Many researchers think this is what will happen to the sun.
However, several scientific models have suggested that the mass of our star is too low to produce a visible planetary nebula—anything less than two solar masses would produce one that would be too faint to see.
Now, an international team of astronomers has shed new light on this issue in a new study published in the journal Nature Astronomy.
The team developed a scientific model which they used to predict the life cycle of stars and the brightness of the nebula associated with different star masses and ages. According to this model, the sun does indeed have the required mass to create a planetary nebula. However, the dust cloud will be relatively faint (albeit, still luminous enough to be visible from neighboring galaxies).
“When a star dies it ejects a mass of gas and dust—known as its envelope—into space,” said Albert Zijlstra, an astrophysicist from the University of Manchester and one of the authors of the new study, said in a statement. “The envelope can be as much as half the star’s mass. This reveals the star’s core, which by this point in the star’s life is running out of fuel, eventually turning off, before finally dying.”
“The hot core makes the ejected envelope shine brightly for around 10,000 years—a brief period in astronomy,” he said. “This is what makes the planetary nebula visible. Some are so bright that they can be seen from extremely large distances measuring tens of millions of light years, where the star itself would have been much too faint to see.”
In the new model, stars are far more likely than in older models to form a bright planetary nebula after they die, beacuse they heat up three times faster when they eject material.
Coincidentally, the new findings also show that the mass of the sun is almost exactly the lower limit for producing a visible planetary nebula. Stars with even minimally lower masses do not produce visible nebulae when they die, according to the scientists.
“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 said.
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