Wednesday , December 8 2021

Astronomers Discover Unexpected Companion Around A Young Star


Protostar MM 1a

Artists impress the disc of dust and gas around the massive protestor MM 1a, with his comrade MM 1b forming in the outer areas. Credit: J. D. Ilee, University of Leeds

Astronomers have captured one of the most detailed views of a young star so far, revealing an unexpected companion on its way around it.

Under observation of the young star discovered astronomers led by Dr. John Ilee of the University of Leeds that it was not a star but two. The main object, called MM 1a, is a young massive star surrounded by a rotating disc of gas and dust that was the focus of the researchers' original investigation. A weak object, MM 1b, was detected immediately past the disc in circulation around MM 1a. The team believes this is one of the first examples of a "fragmented" disc that can be detected around a massive young star.

"Stars form themselves in large clouds of gas and dust in interstellar space," said Dr Ilee, from the School of Physics and Astronomy in Leeds. "When these clouds collapse under gravity, they start rotating faster and form a disc around them. In low-mass stars like our Sun, it's in these slices that planets can form. In this case, the star and the disc we have observed so massively that, instead of witnessing a planet formed in the record, seeing that another star is born. "

Young Star Caught Forming As A Planet

Observation of dust emissions (green) and gas around MM1a (red is decreasing gas, blue approaches gas). MM1b is shown in the lower left. Credit: ALMA (ESO / NAOJ / NRAO); JD Ilee, University of Leeds

Weighing the stars

By measuring the amount of radiation emitted by the dust and subtle shift in the light frequency from the gas, researchers could calculate the mass of MM 1a and MM 1b.

Their work, published today in the Astrophysical Journal Letters, found that MM 1a weighs 40 times our Sun's mass. The smaller circle star MM 1b was estimated to weigh less than half of our Sun's mass.

"Many older massive stars exist with nearby comrades," added Dr. Ilee. "But binary stars are often very similar in mass, and most likely formed together as siblings. Finding a young binary system with a mass ratio of 80: 1 is very rare and proposes a completely different formation process for both objects."

An unstable beginning

The preferred formation process for MM Ib occurs in the outer areas of cold, solid discs. These "gravitationally unstable" discs can not stand up to their own gravity, collapse in one or more fragments.

Dr Duncan Forgan, co-author of the Center for Exoplanet Science at St Andrews University, added: "I've spent most of my career simulating this process to form giant planets around stars like our Sun. To actually see it form something as big as a star is very exciting. "

The researchers note that the newly discovered young star MM 1b could also be surrounded by its own circumstellar disc, which may have the potential to form planets on its own – but it must be quick. Dr. Ilee added: "Stars that are massive like MM 1a only live for about one million years before being exploited as powerful supernovae, so even though MM 1b may have the potential to form its own planetary system in the future, it will not be around for long . "

Image processing objects thousands of light years gone

The astronomers made this surprising discovery by using a unique new instrument high in the Chilean desert – Atacama Large Millimeter / submillimetre Array (ALMA).

By using ALMA 66 individual dishes in a process called interferometry, the astronomers could simulate the power of a single telescope nearly 4 km so that they could form the material surrounding the young stars for the first time.

The team has gained further observation time with ALMA to further characterize these exciting star systems 2019. The upcoming observations will simulate a telescope 16 km above – comparable to the area within the ring road around Leeds.

Paper: G11.92-0.61 MM1: A fragmented Keplerian disk surrounding a Proto-O Star

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