Powerful outbursts of energy from young sun-like stars could be central to how they and their planetary systems form, according to a modelling study. The results hint at a possible explanation for a decades-old astrophysical mystery.
One theory for how stars like our own are born, known as the steady-state concept, makes predictions about how bright young stars should be when they鈥檙e under construction, continuously gathering gas and dust. Yet when we look into the Milky Way, these objects aren鈥檛 anywhere near that bright, and they don鈥檛 appear to be growing quickly enough. Astronomers call this the luminosity problem.
A competing theory examined in the new research 鈥� the outburst model 鈥� suggests that nascent suns brighten dramatically during flurries of feeding as they grow and accumulate, or accrete, material. 鈥淥utbursts solve the luminosity problem by providing episodes of much higher accretion,鈥� says at the University of Nevada, Las Vegas, one of the researchers behind the work. Because such episodes are transitory, that would help explain why we don鈥檛 see young stars blazing brightly all the time.
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As part of the study, the researchers modelled the physical properties and composition of a disc of material around a young sun that had undergone outbursts. They found this scenario did a better job at tallying with observations than the steady-state theory. For example, the outburst model more closely replicated the mix of ingredients measured in primitive meteorites from our solar system, known as carbonaceous chondrites.
The team also suggests that heating from outbursts by the infant sun could shed light on the origins of features in some meteorites called calcium-aluminium-rich inclusions, which appear to have been forged at high temperatures.
, a meteorite expert at London鈥檚 Natural History Museum, says the model in the new study is very promising, but the team鈥檚 assumption about how quickly planet precursors form doesn鈥檛 seem to fit with the ages of some constituents of chondrite meteorites. 鈥淚t seems that whilst the 鈥榞lobal scale鈥� evolution of the solar nebula [the cloud of gas and dust from which the sun formed] is important, modelling it alone is unlikely to explain all meteorite observations,鈥� she says.
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