OU astrophysicist hopes to shed new light on planetary formation

Photo Provided

This artist's conception shows a binary-star, or two-star, system called HD 113766, where astronomers suspect a rocky Earth-like planet is forming around a star. Astronomers suspect the star is at just the right age for forming rocky planets. The two yellow spots represent the stars. The brown ring depicts a belt of dusty material.

NORMAN — There are a few hurdles researchers face when it comes to explaining how the planets in our Solar System, including Earth, formed.

The most obvious of those is that no humans were even close to being alive four billion years ago when the rock and elements necessary for planetary formation all came together. So, astrophysicists like Nathan Kaib at the University of Oklahoma take what they know about how objects move and combine those mathematics in a super computer to create models.

Kaib and collaborator Simon Grimm are hoping to make some progress in this area with a new algorithm that Kaib said allows the computer to take a step back further in time to model planetary formation.

"What we try to do is model how Earth-like planets form, and that is running a simulation of small bodies forming around the sun," Kaib said.

It is hypothesized that the planets in our Solar System -- and those in other star systems across the universe -- formed billions of years ago when rocks and various material began clumping together in an orbit around the sun.

There were billions of these rocks that began sticking together, and that's something even the most powerful computers, like those at the OU Supercomputing Center for Education and Research that Kaib is using, don't have the processing power to model.

So, models begin later in the planetary formation cycle, when the number of objects is smaller and possible to simulate.

"They slowly merge and collapse down into about 1,000 objects," Kaib said. "We model the last stage of that."

This new algorithm will allow computer models to begin a step further back in time when there are slightly more objects to take into account.

Additionally, Kaib said this equation will factor in new theories about planetary formation.

For example, he said the common thought has been that planets form at the same rate regardless of where they are in relation to the sun. But lately, that idea is changing.

"Things grow a lot faster when they're closer to the sun," Kaib said. "If they orbit the sun more quickly, these objects will run into each other more quickly.

"Once you get out to distances like Mars or the asteroid belt, the growth time increases by a factor of 10 or 100.

"In reality, what we probably have is almost full-size planets existing where Mercury and Venus are, and large swarms of objects beyond Earth and where Mars and the asteroids are. That'll change that late stage where everybody models."

This new algorithm also allows computers to model the formation of planets in binary star systems -- basically a system with two suns.

Astronomers know these systems exist and contain planets; there are about 50 planets in binary systems that Kaib will be modeling.

There are two kinds of these binary systems. There is one in which the stars orbit each other so closely that the planets simply orbit everything and there is still one center of mass, just like in our Solar System

But there's another that is more interesting. These are systems were each star orbits each other, but each has its own set of planets orbiting it, and that is what the new algorithm will look at.

"This new code, it's almost like you treat each star as a nested system," Kaib said. "The framework allows you to make this orbital motion assumption, but also to have an arbitrary number of stellar mass objects in a system."

Since stars form in clusters, it is assumed that the first 10 million years or so of a star's life is spent in a binary system. But, as is the case with our Solar System, at some point a star can go solo, and how this happens and how it affects the planets is a question Kaib said he is hoping to answer.

"So if you have a binary star, and a third star flies past it, the gravity is going to distort the binary star's orbit," Kaib said. "If the binary orbit is circular, it is not going to have an effect. But if it is elliptical, it's going to cause a lot of problems with the planets."

The work done in this area will be visible to Oklahoma students, as well. Kaib is partnering with the Sam Noble Oklahoma Museum of Natural History to bring the study of planetary formation to curious schoolchildren.

"One program their department offers is when school groups visit museum, they often sign up for an hour long educational program," Kaib said. "At the moment, they don't have one that focuses on the formation of the earth or solar system. So we're going to work with people in the education department to build one of those programs."

In addition, Kaib will collaborate with the Sam Noble Museum on the creation of Discovery Kits which can be shipped to schools across the state so students outside Norman's orbit will have the exhibits and lesson plans come to them.