For those present yesterday at the astronomy department’s colloquium series, the lecture delivered by Prof. Roman Rafikov, Canadian Institute for Theoretical Astrophysics, Universtiy of Toronto, was nothing less than stellar.
Rafikov’s lecture, entitled “The Origin of Giant Planets and Stellar Disks in the Galactic Center,” focused on the most current research on the formation of the large planets in our solar system: Jupiter, Saturn, Neptune and Uranus, as well as stellar disks, which are rings of stars surrounding black holes.
“We have just recently been getting a lot of data on stellar disks,” Rafikov said during the lecture.
He also spoke about two of the main theories that have been developed by astronomers using the data, and showed that his research supported only one of the theories.
There’s the theory of gravitational instability, he said, which is the theory that large planets begin as a massive cold disk, which becomes gravitationally unstable when the surface density exceeds a certain limit.
“GI (gravitational instability) doesn’t explain how the cores of planets such as Neptune or Uranus were formed,” he said.
Conversely, Rafikov explained that core (nucleated) instability, the theory that protoplanetary cores initially possess massive atmospheres which after reaching a certain core mass dominate gravity and become unstable, is more plausible.
“Core instability is supported by planetesimal accretion,” he said.
Some members of the audience agreed.
“The observational evidence is very strong that gravitational instability is not the primary mechanism for forming the planets that we’ve seen,” said Joe Harrington, a senior research associate, who added, “It was a great talk. I learned a lot.”
While many astronomers are currently researching the beginnings of such celestial bodies, Rafikov’s approach is more physics based and uses analytic techniques to examine the planets. He admitted his lecture was only a brief synopsis of his research.
“My goal was to give an overview of where the research in the field is right now,” he said.
The lecture was delivered as part of the Astronomy department’s Colloquium series and was hosted by Prof. Dong Lai, astronomy, Ph.D. ’94.
“It’s very important to have external speakers come and talk about new developments in the field of astronomy,” he said.
Rafikov’s other research interests include neutron stars, pulsars, and magnetohydrodynamics.