Talk about a happy accidents: Astronomers have unexpectedly stumbled upon a group of young red dwarf stars located not far from our solar system, and their discovery could provide them with the rare opportunity to study slow-motion planet formation.
As reported in the latest edition of the Monthly Notices of the Royal Astronomical, two of the newly-discovered red dwarf stars have large discs of dust surrounding them, a feature that is indicative of planets that are still in the process of forming. Thus, by studying these stars, the astronomers may be able to get a glimpse of a new solar system as it evolves.
“Orbiting disks of dusty material from which planets form are very rare around stars older than 5-10 million years,” lead researcher Dr. Simon Murphy from the ANU Research School of Astronomy and Astrophysics explained to redOrbit via email. “Our serendipitous discovery of two such disks around what we believe are 16 million years stars is therefore very surprising.”
Planets may have more time to form than we thought
The stars were discovered in a young group known as Scorpius-Centaurus, and based on the research, the researchers concluded that either these stars are younger than 16 million years old (meaning that Scorpius-Centaurus has an unexpectedly large age spread) or that disks around stars with masses far lower than the Sun’s last longer than previously believed.
“Because planets are born in these disks, this implies there could be much more time available to form planets than previously thought, especially rocky planets like the Earth which form through the slow build-up of smaller bodies,” said Dr. Murphy, who was aided on the paper by co-author and University of New South Wales (UNSW) Canberra Professor Warrick Lawson.
“There would also be more time for gas giant planets formed early on to migrate within the disk, potentially disrupting the formation of smaller bodies,” he added. “Further observations of these and other nearby disks, especially at infrared and millimeter wavelengths, allow us to construct a detailed picture of disk temperature, structure, chemistry and mineralogy, as well as how these are influenced by the mass of the parent star.”
So why do these red dwarfs still have their discs, anyway?
The mystery remains: Why did these red dwarf stars still have their rings, when other, similarly-aged stars typically do not? Dr. Murphy said this was “still very much an open question.” He told redOrbit that if the mass of the parent star has an influence on the longevity of disks, then the processes through which the disk is cleared of gas and dust (thus halting the formation of gas giants) “must be less efficient around lower mass stars like red dwarves.”
Two possible solutions to this puzzle in the new study, he said. One involves grain growth, in which larger dust grains form more quickly in disks around higher mass stars, rendering them invisible to detection at infrared wavelengths. The other centers around photo-evaporation, where the intense radiation from a star evaporates its disk. Since higher mass stars are more luminous, Dr. Murphy said, they photo-evaporate their disks more rapidly.
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Feature Image: Artist depiction of a dusty disc surrounding a red dwarf. Credit: NASA/JPL-Caltech/T. Pyle (SSC)
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