Scientists from ALMA get new information about a big star through hydrogen masers

 

By National Radio Astronomy Observatory 

January 09 2023

Hidden collimated jets were discovered by scientists using the distinctive hydrogen radio recombination lines on MWC 349A.

Scientists studying the masers orbiting the peculiar star MWC 349A with the Atacama Large Millimeter/submillimeter Array (ALMA) made an unexpected discovery: a previously unobserved jet of material shooting from the star's gas disc at impossibly high speeds. Additionally, they think that the star's powerful magnetic field is what is responsible for the jet. The discovery may aid in the understanding of the makeup and development of massive stars as well as the formation of hydrogen masers in space. In a news conference held today at the 241st annual meeting of the American Astronomical Society (AAS) in Seattle, Washington, the new findings were revealed.

MWC 349A, a star around 3,900 light-years from Earth in the constellation Cygnus, is a hotspot for optical, infrared, and radio studies due to its distinctive characteristics. One of the brightest radio sources in the sky, the massive star is about 30 times as massive as the Sun. It is also one of the few known objects to contain hydrogen masers. By amplifying microwave radio emissions, these masers facilitate the investigation of processes that are otherwise too tiny to observe. This distinct characteristic made it possible for researchers to map the disc of MWC 349A in great detail for the first time.

According to Sirina Prasad, an undergraduate research assistant at the Center for Astrophysics | Harvard & Smithsonian (CfA) and the paper's lead author, a maser is similar to a naturally occurring laser. It's a region of space that produces a very brilliant type of light. We can see this light and determine where it originated from, which puts us one step closer to discovering the truth.

The scientists used the masers to find the previously unknown structures in the star's immediate surroundings by utilising the resolving capacity of ALMA's Band 6, which was created by the National Radio Astronomy Observatory (NRAO) of the US National Science Foundation. The project's principal investigator, senior astrophysicist Qizhou Zhang, added, "We used masers generated by hydrogen to probe the physical and dynamic structures in the gas surrounding MWC 349A and revealed a flattened gas disc with a diameter of 50 au, roughly the size of the Solar System, confirming the star's near-horizontal disc structure. In the winds travelling away from the star, we also discovered a swiftly moving jet component.

Material is being ejected from the star by the observed jet at a searing 500 km per second. That is comparable to going from San Diego, California to Phoenix, Arizona in the span of a single blink of the eye. Researchers believe it is likely that a magnetic force is launching a jet this quickly. A magnetohydrodynamic wind—a form of wind whose motion is controlled by the interaction between the star's magnetic field and gases in its surrounding disk—could constitute that force in the case of MWC 349A.

"According to our prior knowledge, MWC 349A is encircled by a revolving disc and a photo-evaporating wind. There was still no conclusive proof of an extra collimated jet in this system. The jet may be created by a magnetohydrodynamic wind, in which case the magnetic field would be in charge of launching rotating material from the system, according to Prasad. However, we are still unsure of its origin or how it is created. This might aid in our understanding of the interactions between circumstellar discs, winds, and jets in other star systems as well as the disk-wind dynamics of MWC 349A.

About NRAO

The National Radio Astronomy Observatory (NRAO), a facility of the National Science Foundation, is run by Associated Universities, Inc. under a cooperative agreement.

About ALMA

The European Organization for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF), the National Institutes of Natural Sciences (NINS) of Japan, and the Republic of Chile have joined forces to create the Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility. ESO funds ALMA on behalf of its Member States, NSF collaborates with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST), and NINS collaborates with the Korea Astronomy and Space Science Institute and Academia Sinica (AS) in Taiwan (KASI).

The National Radio Astronomy Observatory (NRAO), run by Associated Universities, Inc. (AUI), is in charge of ALMA construction and operations on behalf of North America; the National Astronomical Observatory of Japan (NAOJ), on behalf of East Asia; and ESO, on behalf of its Member States. The building, commissioning, and ongoing administration of ALMA are all coordinated by the Joint ALMA Observatory (JAO).