In the icy darkness of the Taurus molecular clouds, a phenomenal event is taking place. The astronomers from Kyushu University, Kagawa University observed an enveloping ring of hot gas around a young star. This ring was formed by shocks and magnetism during the early stages of stellar formation.
Using the Atacama Large Millimeter/submillimeter Array (ALMA) in its Band 9 high-frequency configuration, the researchers centered their studies on `the CO(J=6 – 5 line to probe the dense core MC 27/L1521F, which contains a Class 0 protostar or early star formation stage. The team used an angular resolve of 300 AU (2 arcseconds) to detect a feature that was almost 1,000 AU in diameter. This had previously been missed by older low-J CO observations.
The protostellar disc, which is a dense cloud of dust and gas surrounding the star, was glowing with a weak light that peaked at around 3 Kelvin. The nearby gas was a bit more complicated. The gas was dense and warm (>=105 moles/cm3) but was surrounded by an ice cocoon and was itself cold.
Its motion and morphology suggest it was formed by localized heating.
This process could have been influenced by the turbulent activity of infalling gas, magnetic fields, or outflows. They act like cosmic sculptors by quickly organizing material and recording the evolution of the protostar in its earliest stages.
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The high-excitation CO-lines provide direct access the dense, warm gas not detected by lower-J-lines.
The new finding opens up a whole new way to investigate the fundamental physics of the early stages of star formation.
Kazuki Tokuda, a first author from Kagawa University, said: Our data revealed that the ring was slightly warmer than it’s surroundings. It is hypothesized that the magnetic field of the protostellar disc produces it. “It’s like the sneezes we have seen in the past but on a larger scale.”
The warm ring that we observed this time confirms that the baby stars are undergoing dynamic gas redistribution soon after their birth. This causes shock waves to warm up the surrounding gases.
Star formation can be hidden by thick clouds of gas and dust. By using the high-J CO, astronomers are able to avoid optical depth limitations, which muffle the systemic velocity in low energy lines, and get a closer look at the energetic processes in the newly formed stars.
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Tokuda was added. We were surprised at the results, as we had not expected to see such a distinct ring.
“I was so excited, I wrote this article in just two or three days.”
It is the first time that such a system has been observed and it highlights the need for multimodal observation. Low-J CO maps show the shape of the cold molecular cloud, while the high-J lines reveal regions that are heated by shocks and where the stellar engines start to operate.
It is more than just an oddity. It is a kind of cosmic nursery that shows how magnetic fields and shocks come together to create stellar architecture. We may be able to discover the blueprint of star formation and planets as ALMA and other observatories continue their investigation into these hidden nurseries.
ALMA will provide additional high-resolution pictures to help study and understand the rings in greater detail.
They plan to dig deeper into ALMA archive data for clues on newborn stars elsewhere in the universe, since this is their first look at the data.
The study was led by Professor Masahiro Machida of the Faculty of Science at Kyushu University. We will continue to collect data in order to support our hypotheses. We welcome a rigorous discussion of our findings to advance the field.
Gas motion in the formation of stars is chaotic and generally orderly. We took a decade before we reached these conclusions. And, as always, we are eager to continue our research to unravel the mysteries of space.
Journal Reference
- Kazuki Tokuda, Mitsuki Omura, Naoto Harada, Ayumu Shoshi, Naofumi Fukaya, Toshikazu Onishi, Kengo Tachihara, Kazuya Saigo, Tomoaki Matsumoto, Yasuo Fukui et al. ALMA band 9 CO(6-5). Reveals Warm Ring Structure in Cold Dense Core L1521F. The Astrophysical Journal Letters.
DOI 10.3847/2041-8213/ae47ec
