The planetary nebula Abell 39 has a diameter of about 5 light years and is about 7000 light-years from Earth.
Credit: T.A. Rector (NRAO / AUI / NSF and NOAO / AURA / NSF) and B.A. Wolpa (NOAO / AURA / NSF)
All stars are dying, and at some point ̵
But after his life is over, what will it look like? Astronomers have a new answer, and their conclusions shine. [Rainbow Album: The Many Colors of the Sun]
The length of the life of a star depends on its size. Our Sun is a yellow dwarf with a diameter of about 864,000 miles (1,390,473 kilometers) or about 109 times the size of the Earth, according to NASA. Yellow dwarf stars live for about 10 billion years, and at 4.5 billion years, our middle-aged sun is about halfway through its lifetime.
Once the hydrogen supply is exhausted, the sun will begin to consume its heavier elements. During this volatile and turbulent phase, massive amounts of star material will be thrown into space as the body of the Sun expands to 100 times its current size and becomes a red giant. Then it will shrink to a tiny, extremely dense white dwarf star, about the size of Earth.
Enlightened by the cooling white dwarf, the cloud of gas and dust that the sun spit into space becomes a swirling red giant. Whether this cloud was visible or not has long been a mystery. An estimated 90 percent of dying stars emit a ghostly halo of dust that lasts for thousands of years. However, computer models introduced decades ago indicated that a star would need to be about twice as large as our sun to create a cloud bright enough to be seen, the study authors say.
However, this prediction did not agree with the sparkle over galaxies. Visible nebulae flashed in young spiral galaxies that were known to host massive stars that could produce glowing dust clouds at the end of their lives.
But even in ancient elliptical galaxies that are populated with stars of low stars, fog shines mass – according to the computer models, these stars could not have produced any visible clouds at all. This puzzling, apparent contradiction is "a long-standing mystery" about the final stages of low-mass stars, the international research team wrote in the study.
We Are Stars And We Are Beautiful  To solve the mystery, scientists developed a new computer model for predicting the life cycles of stars.
According to their new calculations, when expanding red giants eject the dust and gas that make up the mist, they heat up three times faster than suggested by the previous models. This accelerated heating would allow even a star of lesser mass, like our Sun, to show a visible fog.
"We found that stars with a mass less than 1.1 times the mass of the sun produce weaker nebulae that are more massive than 3 solar masses [produce] lighter nebulae," said study co-author Albert Zijlstra, a professor of astrophysics the University of Manchester in the UK, in a statement.
"But for the rest, the predicted brightness is very close to what was observed," Zijlstra added. "Problem solved, after 25 years!"
The results were published yesterday (May 7) in the journal Nature Astronomy online.
Original article on Live Science .