Astronomers surprise an “intruder” in the heart of a star system

He clearly broke in. This “intruder” that astronomers have surprised at the heart of the star system Z Canis Major (Z CMa). But for the first time, they were able to take his footprints and trace the disturbances he caused in the protoplanetary disc. What will the consequences be ?

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The constellation of the Grand Dog is known to host thebrightest star from our sky nocturne, Sirius. There is also a binary system baptized complex Z Canis Major (Z CMa). Ce star system formed only 300,000 years ago, from two stars separated by about a hundred times the Earth-Sun distance. Stars both more massive and brighter than ours.

And it is in this system that astronomers have just reported a rarely observed event. The passage of a “Intruder”. An object that approached and interacted with the environment of the Z CMa star system, causing the formation of chaotic and stretched streams of dust and gas in the disc that surrounds it. A bit like what happens when several neighboring stars are born simultaneously. Intruder passages appear regularly in simulations, but there are few convincing observations.

The researchers explain that the transience of this type of event makes them difficult to observe. A bit like for those who would like to photograph the lightning hitting a tree. The evidence that astronomers have been able to gather this time seems to show that young stars can actually get closer.

New instruments for more observations

What astronomers have recorded is a sort ofdigital print the passage of the intruder. Changes in the morphology protoplanetary disc that reveal its presence. And which push the researchers to wonder about the influence that the event could have on the formation of planets possibly underway in the Z CMa system. Because, as the data collected here prove, such intrusions deeply disturb the protoplanetary disks surrounding these stars.

They can also impact the thermal history of the stars in the system and cause violent events of the accretion brutal. All of this remains to be determined. But it is certain that if astronomers manage to observe more of these intruder passages, they will also be able to better understand what happened at the time of the formation of our Solar system.

To do this, they may have to wait until the planned upgrade of theAtacama Large Millimeter/submillimeter Array (Alma) and the commissioning of the new generation of Very Large Array (VLA). Both projects are ongoing. And they should increase the chances of observing intruder passages in star systems.

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