Physics lecture explores planet formation misconceptions, realities

By Robyn Sanders

The Fall Physics Colloquium series is set to continue today with a lecture detailing how planets are made. Dr. Victor Land, a postdoctoral research associate at Baylor, will give an hour-long lecture, “The Early Stages of Planet Formation,” today at 4 p.m. in E125 of the Baylor Sciences Building.

The series, which began Aug. 31, is intended for both undergraduate and graduate students, as well as faculty, and is also open to the public.

“The reason that we do this is … to expose the students at the undergraduate and graduate level to different kinds of physics and to get an idea of all the different kinds of problems that you could work on and solve using physics,” said Dr. Lorin Matthews, assistant professor of physics. “And then also for the faculty, it’s also interesting to keep abreast of what other people are doing either in your field, or just to learn about physics in a field that’s completely unrelated to yours. So it’s a whole sharing of ideas.”

Land will lecture specifically on dust aggregation in proto-planetary disks, which are clouds of gas and dust that form a disk shape.

Proto-planets refer to objects that are not planets yet, but could be considered the “seeds of planets,” Land said.

The aggregating dust particles inside the disk should eventually become planets, Land said.

“We actually look at really tiny dust particles, which are about the width of your hair, or less, in size,” Land said. “What you call dust aggregation is basically collisions between these really small particles, and how they stick together and form larger and larger structures.”

Land also said that although planets are common, solar systems like ours are rather rare.

“That kind of means that all the ideas we have about planet formation, which mostly are based on what we observe in our solar system, are naturally wrong, or off, or incomplete,” Land said. “So that’s why we still need to look at these tiny, tiny specks of dust colliding and sticking, even though it sounds completely remote from planets, but it’s actually an essential part of it.”

Another important aspect of proto-planetary disks is the interaction of dust and plasma.

Matthews said plasma is created when a gas is heated so that it loses an electron. The plasma is then able to stick to the dust and charges it.

“A lot of people do the same research but consider plasma to be unimportant,” Land said, “which means that the whole concept of the charging of dust particles is neglected, and we feel that that’s actually essential.”

Matthews said that a dynamic computer model is used to figure out what happens when two particles approach each other.

Using this animated model, bigger populations of particles can be built up.

By building up thousands of particles in the computer model, they can get a trend for the population of dust particles, which can then be recreated in the lab.

“In the lab, we have a device that actually creates the plasma inside of it; it’s called a reference cell,” Matthews said. “It’s a vacuum chamber in which we ignite a plasma. So then, we actually buy dust that is spherical and all the same size … and we drop it in from the top of the cell. By changing the conditions inside of the cell, we can actually form aggregates.”

Matthews said little clumps of dust will aggregate inside the cell and form 3-D structures.

Then a camera with a microscope lens will capture images of the aggregates in the cell.

“These particles are like 10 microns in diameter, and your hair is 100 microns in diameter.” Matthews said. “By looking at the pictures of them, then we can recreate a computer model of the aggregates, and then use those actually in our numerical model, and compare the behavior that our computer program predicts to the behavior that we actually observe in the cell.”

The series will continue weekly.