An NMSU professor co-authored a paper proposing an alternative theory of planet formation
LAS CRUCES – Astronomers can’t go back in time to observe how the solar system formed, but they can observe the planets forming now and use computer simulations to help them better understand the process.
A New Mexico State University astronomy professor is part of a team of scientists who authored a paper published this month in the journal ‘Nature’ that identified a protoplanet in another star system which could form differently than expected. It is the first system in which evidence points to this alternative theory of planet formation.
The article, “Images of the Formation of a Jovian Planet Embedded in a Broad Separation Around AB Aurigae”, was published in the May 9 edition of the journal “Nature” and co-authored by Wladimir Lyra, associate professor of astronomy at New Mexico State University.
“The ultimate arbiter of science is nature. We have to observe what nature does. Then, to advance our knowledge, we build models to explain our observations,” said Lyra, who builds computer models based on astronomical data.
The recent paper is the result of Lyra’s collaboration among a group of scientists including lead author Thayne Currie, an astrophysicist at NASA-Ames Research Center and the Subaru Telescope. Currie, along with other researchers, shared observational data of the protoplanet forming around AB Aurigae, a very young star in the constellation Auriga about 531 light-years from the Sun.
“It’s not even a baby planet. It’s an embryonic planet,” Lyra said. “It’s a planet that is still embedded in the disc. These planets form from gas and dust around young stars. This is how the Earth and the other planets around the Sun were formed.
Using the Subaru Telescope and the Hubble Space Telescope, researchers found the data on this particular protoplanet to be intriguing and difficult to explain. Lyra has created a computer simulation to match observations and better understand the process of formation of this huge gas giant planet.
What they found is unexpected.
“On this particular sighting, what was observed was a planet 10 times more massive than Jupiter at a distance from the star that is twice the distance Pluto is from the sun,” Lyra said. “This planet is still embedded in the disk. It is also still very hot. You can see that the object is still glowing since its formation.
For decades, scientists have relied on two theories about the formation of planets and stars. One is core accretion, also known as “rising,” when small asteroid-sized bodies collide and coalesce into a disk cloud, eventually adding gases and growing particles. massive planets the size of Jupiter or Saturn.
The second theory of planet formation is gravitational instability, also known as “top down”. This theory begins with a massive disk of dust and gas so large that it eventually shatters. In a disk around a star, these fragments collapse from top to bottom and are about as massive as Jupiter. It is the process by which massive stars form in a galaxy.
Although the theory of gravitational instability forming planets has been around for decades, there have been no clear cases demonstrating that a planet could be formed in this way. The article “Nature” presents evidence that the protoplanet observed around AB Aurigae is such a planet, contradicting long-established theories.
“I think the main message from a theoretical perspective of this paper is that this is a system for which gravitational instability is a plausible mechanism for the formation of this protoplanet,” Lyra said. “There are several independent lines of evidence that point to gravitational instability.”
Lyra pointed out while the evidence points to the formation of this protoplanet by gravitational instability, so far this does not disprove the possibility that it formed by the method of core accretion.
The team will continue to examine this system in longer wavelengths, probing deeper into the disk. Lyra called it “a very interesting avenue to explore in the future to see if there are any conditions that this planet can still form through core accretion.”
“EYE ON RESEARCH” is provided by New Mexico State University. This week’s article was written by Minerva Baumann of NMSU Marketing and Communications. She can be reached at 575-646-7566 or [email protected].