More than 450 light-years distant, in the center of a dense cloud of gas and dust, is a recently discovered bubble structure that is the physical representation of a pair of young stars undergoing star formation.
In the Taurus molecular cloud complex, an astronomical team has discovered a bubble at the center of a stellar nursery known as Barnard 18 that was likely carved out of the surrounding gas when two developing stars therein developed and expanded.
It’s only the second time that astronomers have discovered such a bubble related with the ‘outflow’ of material from a developing star.
Scientists may be able to understand more about how the environment affects stars as they grow thanks to the recently found structure.
Star creation is a chaotic, complex process. A dense, chilly cloud made up of tiny dust grains and gases, including hydrogen, is where it all begins.
A chunk of this cloud eventually dissipates in a swirl under the force of its own gravity, absorbing more particles from the surrounding material fog.
Once it has amassed sufficient mass, the resultant pressure and heat produce the hydrogen that gives stars their core.
However, when a young star gathers mass, it lashes out at the area around it. Not all of the material enters the star; some is accelerated along the magnetic field lines of the protostar towards the poles, where it bursts into space as astrophysical jets.
Feedback is the name given to these outflows, which are thought to be crucial in both stopping protostellar growth and the development of the interstellar medium, the gas and dust that floats around in the voids between stars.
Because molecular clouds are so dense, it is difficult to detect what is happening inside of them when a star forms. Longer wavelengths of light can pass through the cloud, but shorter ones cannot.
The nebula known as Barnard 18 is dark and neither emits nor reflects light. Optical observations show it to be a dark smudge that resembles a gap in space.
Molecular Bubble Discovery
Therefore, a group of astronomers from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) in China went to radio frequencies to look inside the cloud. The team was led by Yan Duan and Di Li.
They examined the carbon monoxide signal, which may be used to identify structures within a gas cloud, using two separate radio telescopes. The Barnard 18 molecular cloud also had signs of a bubble structure, which they discovered. Even more was revealed after more observations.
“Through combined analysis with the Five College Radio Astronomy Observatory (FCRAO) survey of the Taurus molecular cloud, we found an outflow located at the center of the molecular bubble,” says NAOC astronomer Yan Duan, first author on the team’s paper.
The Herbig-Haro object known as HH 319, which has already been recognized by astronomers, resides on Barnard 18.
These are made when protostellar jets, which are propelled away from their source stars at extremely high speeds, collide with the molecular cloud and induce luminosity.
Li and his team’s discovery of HH 319 near the core of the outflow provides information on the bubble’s origin.
However, there were a number of potential progenitors: stars don’t always remain motionless; there was no star seen at the heart of the bubble; and numerous young stars can be detected close by.
The scientists determined the origin to be a binary pair of T Tauri stars based on their position.
These are a particular class of young star that haven’t fully started hydrogen fusion and are still gaining mass.
The scientists discovered that the binary is the one that is most likely to have travelled from the bubble’s center to its current location.
Calculations by the scientists indicate that activity from the two stars began sculpting the massive bubble in Barnard 18 around 70,000 years ago.
This, according to the study, shows how T Tauri stars have the power to significantly alter their immediate environment. Future observations will be required to validate their findings, though.
To read our blog on “A new era of stars promised by the James Webb telescope,” click here.
