Baby stars, just like baby humans, may experience rapid growth spurts in their infancies, according to one theory of star formation. But it has been challenging for scientists to directly observe this process because baby stars tend to be obscured behind the gas and dust in their parent molecular clouds.
Enter G358-MM1, a massive protostar located some 22,000 light years from Earth. In January 2019, astronomers witnessed a rapid flare of intense “masers,” which are like lasers in the microwave part of the light spectrum, around this maturing star. The burst indicates that this baby star had sent out a powerful “heatwave,” an event rarely captured by astronomers, according to a recent study in Nature Astronomy.
Led by Ross Burns, an astronomer at the National Astronomical Observatory of Japan, the study’s authors show that the heatwave was fueled by an accretion burst, which means that the baby star suddenly gulped down a large helping of gas and dust from its surroundings. The influx of new material triggered a flare of thermal radiation that emanated out from G358-MM1 at about 8 percent of the speed of light.
Accretion bursts have been witnessed in two other young stars, with the first ever detection in 2016. But Burns’ team is the first to coordinate follow-up observations from several radio telescopes, after the initial detection from the Hitachi Telescope in Ibaraki, Japan.
As a result of the follow-ups, the new G358-MM1 findings “constitute the first intensive observational campaign conducted during the onset of an accretion burst in a high-mass star,” Burns and his colleagues said in the study. This multi-telescope strategy was developed by the Masers Monitoring Organization (M2O), an international collaboration of scientists dedicated to flagging masers in order to learn more about the birth of massive stars, among other cosmic phenomena.
The new research supports the theory that high-mass stars go through necessary episodic accretion events, which spark these detectable heatwaves, as part of their formation process. As opposed to growing at a steady rate, stars like G358-MM1 are fed huge clumps of dust and gas that fuel their evolution into high-mass stars.
The data obtained by the super-group of radio telescopes also found that the accretion burst from G358-MM1 had a different profile from the previous two detections. The pulse of masers around the young star sparkled and faded more rapidly than the two bursts, and was not quite as luminous.
“The G358-MM1 event may therefore represent a new species in a zoo of high-mass protostar accretion-burst varieties,” the team concluded in the study. “It is likely that this class of events will diversify as more follow-up investigations of accretion bursts are reported.”
In other words, scientists are developing methods that are equivalent to ultrasounds for embryonic stellar systems, which could resolve many outstanding questions about the birth and maturation of these gigantic, mysterious stars.