Study sheds light on the feeding habits of young stars
According to new research, young stars may gain mass by consuming dense clumps of matter that may themselves have gone on to evolve into giant planets. The clumps are believed to be devoured by a star periodically, with intervals of several thousand years between "meals." During periods of brightness following the consumption of one of the cosmic clumps, astronomers estimate that a star could burn up the equivalent of the Earth's mass once every 10 days.
Bodies such as our Sun form in vast swirling clouds of gas and dust that eventually coalesce to form a new star. However, this process does not consume all of the surrounding matter, the remainder of which forms what is known as an accretion disk around the freshly-born star.
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It had previously been a matter of debate as to how material from this disk was transferred to the infant star, allowing it to grow in mass. The prevailing theory held that the disk steadily fed matter to the infant star, until the cosmic clouds had been exhausted in the process of swelling the stellar body, and creating accompanying planetary bodies.
However, this theory would fail to explain a phenomena observed in young stars, in which the stellar bodies suddenly increase in brightness by a factor of 250 in only a year. This suggests a massive infusion of new material that could not be the case if the star was being fed a steady stream of matter.
The new study provides evidence for a separate theory, which, first proposed 10 years ago by Eduard Vorobyov of the Vienna University, espouses a more violent process for star formation. Vorobyov believed that gravitational instabilities within the structure of the disk cause highly dense clumps of gaseous material to coalesce, and subsequently fall into a young star.
The international team of researchers made use of the SUBARU 8.2 m (27 ft) optical infrared telescope located at the Mauna Kea telescope, Hawaii in order to isolate arms and arcs in the accretion disks surrounding four young stars – key features synonymous with the gravitational fracturing model.
"This is a major step towards our understanding of how stars and planets form and evolve," states Vorobyov, "If we can prove that most stars undergo such episodes of brightening caused by disk gravitational instability, this would mean that our own Sun might have experienced several such episodes, implying that the giant planets of the solar system may in fact be lucky survivors of the Sun's tempestuous past."
Source: University of Vienna