Jess Speedie, a PhD candidate at the University of Victoria (UVic), has helped solve one of the universe's many mysteries. 

Most physicists and astronomers have believed that planets form via core-accretion, whereby particles in a star's protoplanetary disk B次元官网网址� a rotating, Frisbee-shaped cloud of gas and dust B次元官网网址� stick together over millions of years. 

B次元官网网址淭he stuff that the planets form out of is basically the leftovers of the starB次元官网网址檚 formation," said Speedie. "You have many small particles and they ... conglomerate into larger and larger objects until, eventually, you get a planet.B次元官网网址�  

For decades, however, others have theorized that planets can form in another way, as result of gravitational instability in a starB次元官网网址檚 disk. In these cases, some physicists and astronomers argued that the gaseous Frisbees can be so massive and dense that matter can drift away from stars, resulting in the formation of spiral arms. 

"In the spiral arms, that's where you have regions of higher density, and those spiral arms basically fragment into clumps, and those clumps go on to further collapse into giant planets," said Speedie, who added that these planets can form in just thousands of years, as opposed to millions. 

However, there has been no proof to support this theory B次元官网网址� until now. 

In 2020, Dr. Cassandra Hall, an assistant professor of computational astrophysics at the University of Georgia, predicted that the disks surrounding gravitationally unstable stars emit detectable radio-wave signatures.  

B次元官网网址淪he discovered the equivalent of a COVID test, but to tell whether or not a disc is gravitationally unstable,B次元官网网址� said Speedie. 

To put her prediction to the test, in 2022, Hall and a team of 10, which included Speedie and Ruobing Dong, an assistant professor of astronomy and physics at UVic, secured time on the Atacama Large Millimeter Array (ALMA), a telescope located in a high-elevation desert in northern Chile.  

ALMAB次元官网网址檚 operators soon aimed the 66-antenna machine at AB Origae B次元官网网址� a star 529 light years away from Earth. Not long before, physicists and astronomers discovered planets circling the distant A-type star whose formation couldnB次元官网网址檛 be explained by core accretion B次元官网网址� an indicator that the starB次元官网网址檚 disk is gravitationally unstable. 

For two years, Speedie poured over the radio waves ALMA collected in search of gravitational instability signatures. Then, two years later, in 2024, Speedie found what she was looking for, proving HallB次元官网网址檚 test accurate. This confirmed that the planets in AB OrigaeB次元官网网址檚 disk formed via gravitational instability B次元官网网址� a discovery of huge significance.

"To understand the planet-formation process will help us understand how we get this diversity of planets around other stars," said Speedie, who added that the next step for future research is to observe other young stars and build statistics about how often planets form via gravitational instability.

The finding could also shed light on other mysteries, including those closer to home.

B次元官网网址淸Planets are] where the life could be,B次元官网网址� she said. B次元官网网址淭hat's where you could have consciousness. It's not going to happen on the surface of stars, it's not going to happen on the surface of black holes. Planets are where the stories happen.B次元官网网址� 

"How did Earth form? How did Jupiter form? Is our solar system unique in this diversity of planets in the Milky Way?B次元官网网址� Speedie added. B次元官网网址淲e want to know our own origin stories. We want to know how we got here."