MYSTERIES OF THE UNIVERSE
WHAT DISTURBED A DISTANT STAR SYSTEM?
Astronomers are a step closer to understanding how our Solar System formed, all thanks to a chance encounter
Reported by David Crookes
One of the greatestmysteries that astronomers hope to one day solve is how our Solar System formed. It’s long been known that star systems are shaped by collisions and other disruptive events, so whenever scientists are lucky enough to directly observe such an occurrence, it takes researchers one step closer to the answer.
In 2021, scientists made a breakthrough. They used the Atacama Large Millimeter/ submillimeter Array (ALMA), along with the Karl G. Jansky Very Large Array (VLA), to peer at the Z Canis Majoris (Z CMa) star system. They wanted to study a stream of dust and gas that was stretching far into the darkness of space. In doing so they happened to capture an object which they could see had smashed into the protoplanetary disc of leftover material surrounding the protostar pair, and it got them very excited indeed.
Z CANIS MAJORIS STAR SYSTEM BY NUMBERS
300,000
years old
THREE
Probable number of stars – the two in the central binary plus the flyby, likely also a star
100
Distance between the stars in astronomical units
3,750
Light years from Earth
2,000
Length of the streamer in astronomical units
4,700
AU to the flyby object that disrupted Z CMa
2021
Year the object was discovered
TWO
Sets of telescopes used to find the object
ONE
telescope saw the streamer but not the object
Although astronomers had previously observed the effects of the collision – the streamer, as it’s referred to – this time researchers found something else. “We detected it almost purely by chance,” says Ruobing Dong, an astronomer at the University of Victoria in Canada and principal investigator of the study. “It was like going on a hiking trip, finding a beautiful leaf on a tree and taking a photo of it, only to examine the photo afterwards and find lightning in the background sky.”
What they saw was the object that appeared to have caused the collision – something that wasn’t even bound to the Z CMa star system and instead came from elsewhere. The intruder had flown past, collided with and smashed a chunk of the protoplanetary disc away. The discovery may have been sheer luck, but it was nevertheless a chance observation that would prove to be of great importance. “We’d pointed ALMA and the VLA to Z CMa at the time to study its streamer, and the flyby object just showed up in the photo. It was kind of a surprise.”