Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have captured a stunning image of two circumstellar disks in which two protostars are growing, fed by a complex network of filaments of gas and dust.
![This ALMA image shows the binary protostar [BHB2007] 11. Image credit: ALMA / ESO / NAOJ / NRAO / Alves et al.](https://cdn.sci.news/images/enlarge6/image_7662e-BHB2007-11.jpg)
This ALMA image shows the binary protostar [BHB2007] 11. Image credit: ALMA / ESO / NAOJ / NRAO / Alves et al.
Dr. Felipe Alves of the Max Planck Institute for Extraterrestrial Physics and colleagues used ALMA to conduct the high-resolution observations of [BHB2007] 11, a binary protostar located in the constellation of Ophiuchus, about 700 light-years away.
This system is the youngest member of a small cluster in the Barnard 59 dark nebula, which is part of the clouds of interstellar dust called the Pipe Nebula.
“We see two compact sources that we interpret as circumstellar disks around the two young stars,” Dr. Alves said.
“The size of each of these disks is similar to the asteroid belt in our Solar System and the separation between them is 28 times the distance between the Sun and the Earth.”
The two circumstellar disks in [BHB2007] 11 are surrounded by a bigger disk with a total mass of about 80 Jupiter masses, which displays a complex network of dust structures distributed in spiral shapes.
“This is a really important result,” said co-author Dr. Paola Caselli, also from the Max Planck Institute for Extraterrestrial Physics.
“We have finally imaged the complex structure of young binary stars with their feeding filaments connecting them to the disk in which they were born. This provides important constraints for current models of star formation.”
The protostars in [BHB2007] 11 accrete mass from the bigger disk in two stages.
The first stage is when mass is transferred to the individual circumstellar disks in beautiful twirling loops, which is what the new ALMA image showed.
The data analysis also revealed that the less-massive but brighter circumstellar disk — the one in the lower part of the image — accretes more material.
In the second stage, the stars accrete mass from their circumstellar disks.
“We expect this two-level accretion process to drive the dynamics of the binary system during its mass accretion phase,” Dr. Alves said.
“While the good agreement of these observations with theory is already very promising, we will need to study more young binary systems in detail to better understand how multiple stars form.”
The study was published in the journal Science.
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F.O. Alves et al. 2019. Gas flow and accretion via spiral streamers and circumstellar disks in a young binary protostar. Science 366 (6461): 90-93; doi: 10.1126/science.aaw3491
