AsianScientist (Jul. 25, 2019) – An international team of astronomers has obtained the first detailed face-on view of a gaseous disk feeding the growth of a massive baby star. Their discovery is published in the journal Astrophysical Journal Letters.
A protostar, a baby star still in the process of forming, is fed by a surrounding disk of gas falling towards the center. The details of the process, such as why stars form with a wide range of masses, are still unclear.
Low-mass stars are typically formed in the vicinity of our solar system, allowing astronomers to observe the process up-close. On the other hand, massive protostars are rare, and even the nearest ones are located quite far away from us.
In this study, researchers led by Assistant Professor Kazuhito Motogi at Yamaguchi University, Japan, used the Atacama Large Millimeter/Submillimeter Array (ALMA) to observe a massive protostar called G353.273+0.641 (hereafter named G353). Located 5,500 lightyears away in the Scorpius constellation, G353 has a mass 10 times larger than the Sun, and is still growing.
G353 is a unique target among massive protostars because scientists can observe its gaseous disk from directly above, giving them a top-down view of the process. ALMA has revealed detailed views of several other massive infant stars, but most of them are in edge-on configurations, making it difficult to see the inner regions of the disks.
ALMA observations captured a rotating disk around G353 with a radius eight times larger than the orbit of Neptune. This sounds huge, but it is one of the smallest disks yet found around a massive protostar. The astronomers also noted that the disk is surrounded by an envelope of gas three times larger than itself.
“We measured the gas in-fall rate from the outer envelope to the inner disk,” said Motogi. “This helps us to estimate the age of the baby star. Surprisingly, it is only 3,000 years old, the youngest among known massive protostars. We are witnessing the earliest phase of the growth of a giant star.”
The team also found that G353 shares many common features with lighter baby stars. This implies that the process of star formation is the same, regardless of the final mass of the resulting star. This finding paves the way for a more complete understanding of star formation, said the researchers.
The article can be found at: Motogi et al. (2019) The First Bird’s-eye View of a Gravitationally Unstable Accretion Disk in High-mass Star Formation.
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Source: National Institutes of Natural Sciences; Photo: National Astronomical Observatory of Japan.
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