April 12, 2012
Dying Stars Are The Building Blocks Of Future Planets
Lawrence LeBlond for RedOrbit.com
Scientists report in a new study that they have solved a long-standing mystery about how dying stars release their precious matter, compounds that are an important ingredient in the building blocks of future planets.
Their discovery was made after observing the violent ends of three ℠red giants´ having their atmospheres ripped away by super winds containing dusty grains of silica, producing massive sandstorms in space. These grains were unexpectedly large in size for stellar wind particles, measuring nearly a micrometer across, the scientists said.
The breakthrough study was conducted by researchers at the University of Sydney, Australia, and published in the journal Nature today, April 12. They used the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Chile for their observations.
The researchers noted that the solution of the mass loss problem has profound implications across astronomy and beyond. Scientists previously knew that many stars end their lives ejecting upwards of half their masses over approximately 10,000 years, but until now, it has been unclear how the matter is blown into space, sometimes at speeds approaching 20,000 mph.
The University of Sydney team now knows the answer to that longtime puzzling question.
“The winds that stream from the upper atmosphere of the red giant stars are responsible for removing massive amounts of matter,” said lead author Barnaby Norris, a PhD student from the University's Faculty of Science.
Using the VLT in Chile, Norris and his colleagues created images of the faint starlight emitting a halo of dust grains around three red stars.
“The grains that we have discovered here will come as a real shock to the accepted wisdom in the field. They are both much larger and much closer to the stellar surface than anyone expected,” said Norris, noting that this could be a critical piece of the puzzle in determining how these old, dying stars manage to drive such powerful winds.
“These myriad specks of dust seem entirely unimportant individually, but each one can act as a minute solar sail catching the rays of light from the star and adding its infinitesimal push to the gas, creating the wind,” added study coauthor Professor Peter Tuthill, director of the Sydney Institute for Astronomy.
“Even more remarkable, the grains themselves are transparent like powdered glass, but so incredibly fine so as to appear like smoke. It is hard to imagine such a glittering halo doing the heavy lifting of more than an entire earth each year,” said Tuthill.
Norris told BBC News that these dying stars that produce massive halos of grain, and sending particles through space at incredible speeds, are in fact “the galaxy´s great recyclers.” He added that the material that is spewed out from these red giants “goes on to make the next generation of stars and planets.”
Eventually, after the red giant spews out most of its matter, only a dying and fading ℠white dwarf´ is left. Our own Sun will begin this process in about five billion years, after expanding in size to become a red giant.
Amazingly, the dust and grains the superwinds drive through space ultimately become the building blocks of other planets.
“The dust and sand in the superwind will survive the star and later become part of the clouds in space from which stars form,” Professor Albert Zijlstra of the University of Manchester´s Jodrell Bank Observatory told The Daily Mail. “The sand grains at that time become the building blocks of planets. Our own Earth has formed from star dust. We are now a big step further in understanding this cycle of life and death.”
The majority of the chemical elements critical to the formation of earth-like planets and life come from the winds driven from dying red giants, added Norris. “That means the Earth and everybody living on it are quite literally made of the stardust we are studying with our new techniques.”
“Hopefully our findings will help to illuminate a key step in the grand cycle as matter is expelled from stars into the galaxy only to seed new generations of stellar and planetary birth,” said Norris.
“The mechanism by which mass is transported away from these stars is one of the biggest questions in stellar astronomy, and underpins our whole understanding of how heavy elements are spread throughout the galaxy. Our study is just one small piece in this puzzle,” Norris concluded.
Astronomers from the Australian Astronomical Observatory, Paris Observatory and the University of Manchester contributed to this research.