Astronomers discover strange new ‘molecular bubble’ structure in space
(ORDO NEWS) — The newly discovered structure, located deep in the heart of a thick cloud of gas and dust more than 450 light-years away, is a sign of a pair of young stars in the process of forming.
A team of astronomers has discovered a previously invisible bubble at the center of a stellar nursery called Barnard 18 in the Taurus molecular cloud complex, likely carved out of the surrounding gas as two nascent stars formed and grew in it.
For only the second time, astronomers have identified such a bubble as an ejection of material, or “outflow,” associated with a growing star.
The newly discovered structure could help scientists learn more about how stars affect their environment as they grow.
Star formation is a complex and intricate affair. It begins with a dense cold cloud of fine dust particles and gases, including hydrogen.
Eventually, the clump of this cloud collapses in a whirlpool under its own gravity, pulling in more material from the surrounding fog of material.
Once it has gained enough mass, the resulting pressure and heat creates hydrogen at the core that defines stars.
But as the young star accumulates this mass, it pounces on the space around it.
Not all of the material ends up in the star; some of them accelerate along the magnetic field lines of the protostar to the poles, from where they fly out into space in the form of astrophysical jets.
In addition, protostars cause winds that carve huge voids in the cloud from which they were born.
These outflows are called feedback, and they are thought to play an important role in stopping protostellar growth as well as the evolution of the interstellar medium gas and dust drifting through the space between stars.
Because molecular clouds are so dense, it’s not easy to see what’s going on inside them as a star forms. Light with shorter wavelengths does not penetrate the cloud; but longer waves can.
Barnard 18 is a dark nebula that neither emits nor reflects light. In optical observations, it looks like a dark spot, almost like a void in space.
So, to look inside the cloud, a team of astronomers led by Yang Duan and Di Li at the National Astronomical Observatory of the Chinese Academy of Sciences (NAOC) in China turned to radio waves.
Using two different radio telescopes, they analyzed the carbon monoxide signal, which could be used to track structures in the gas cloud. And while hiding in Barnard 18’s molecular cloud, they found signs of a bubble structure.
Further observations revealed even more.
“Through a joint analysis with the Five Colleges Radio Astronomy Observatory (FCRAO) study of the Taurus molecular cloud, we have detected an outflow located at the center of the molecular bubble,” says NAOC astronomer Yang Duan, first author of the group’s paper.
Barnard 18 is home to a curious object that has already been identified by astronomers – a Herbig-Haro object called HH 319.
They are created by protostellar jets ejecting from their parent stars at incredible speeds, colliding with the molecular cloud and causing it to glow.
HH 319 is located at the center of the outflow identified by Lee and his team, and this provides a clue to the origin of the bubble.
But there were several possible progenitors: the stars do not always sit still, not a single star was visible in the center of the bubble, and several young stars can be found nearby.
Based on their position, the researchers traced the origin to a binary pair of T Tauri stars. Y younger than a million years is a type of star that hasn’t started fusing hydrogen yet and is still accumulating mass.
The team found that the binary system most likely moved to its current position from the center of the bubble.
According to the team’s calculations, the activity of the two stars is about 70,000 years. ago, a giant bubble began to form at Barnard 18.
This, the team says, demonstrates the ability of T Tauri stars to have a significant impact on the environment. However, future observations will be needed to confirm their findings.
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