Pomona Astronomers Contribute to Groundbreaking Study of Near-Earth Asteroids

Bryan Penprase, Pomona College’s Frank P. Brackett Professor of Astronomy and Department Chair, along with Catherine Wilka PO ’12 and Alex Hagen HM ’10, are contributing to the largest-ever study of near-earth objects (NEOs). They are part of an international group called the ExploreNEOs team.

“It is the first systematic attempt to characterize near-earth objects, and to systematically do it over a sample that is large enough to give a representative sample,” Penprase said. “There are something like 5,000 that are known, and our sample targets about 10 percent of them.

“Our sample is going to get optical data, infrared data and spectroscopic data,” he added.

According to Penprase, these kinds of studies have only recently become possible thanks to the advance of observation techniques.

“The objects in those areas are small and very faint, and they tend to be moving very quickly, and so they are difficult to study,” Penprase said. “Only now do we have the tools that enable us to understand the nearby universe, the stuff right between earth and moon in some cases.”

He explained that the technology used to observe these objects is extremely new.

“It requires using infra-red telescopes like the [NASA] Spitzer space telescope, which was launched a few years ago, and using big ground-based telescopes,” he added. “There are now dozens of them that can look in the infra-red and the optical wavelengths and are able to track these things as they move through the sky and get accurate measurements.”

The research is also remarkable for its practical applications.

“Every day, in fact, there’s something like a hundred tons of material that fall on Earth from space,” Penprase said. “We don’t really even understand where all this stuff is coming from…. This is the only astronomy research I’ve ever done where I can truthfully say that the results could impact the survival of our planet. That gets people’s attention. And yet it is literally true that this is an earth-shattering area of research.”

When NEOs impact Earth, they can have tremendous consequences for the planet, even—once every 60 million years, at least—drastically altering the climate and causing mass extinctions.

“Congress wants a lot of these things catalogued and categorized,” Wilka said of the potentially dangerous objects.

Penprase organized the Pomona contingent of the project, which has been at work for about two years.

“I didn’t start out doing solar system work, but I found through the years here at Pomona that solar system objects are a lot of fun for students and easily observed with our telescopes.”

Penprase said that the Pomona group’s role “is to get the ground-based optical data for the project.”

“We started out just helping them think about the problem and offering our services in terms of having an eager crew of students who could take data with our telescopes,” he said. “We’ve since been gathering data on these little guys using both our local telescope [Table Mountain Observatory] and trying out observations with Brackett, and also a robotic telescope out in New Mexico.”

A group from Pomona has twice been to Chile to take ground-based data. The group’s most recent trip took place from Oct. 6 to 15.

“I observed seven nights, and I had about a day and a half transit time in-between,” Wilka said of the trip.

Though Wilka is more interested in theoretical astronomy than observational astronomy, she has found her participation in the project very rewarding.

“I’ve gotten a lot more familiarity with using different telescopes and feeling confident about working with those instruments,” she said. “I’ve learned much more about computer analysis of data.

“This is the first time that I’ve really kind of gotten in touch with the greater astronomical community,” she added. “It’s been really cool to meet people in the field.”

The larger ExploreNEOs study was begun by the astronomer David Trilling of Northern Arizona University, and he continues to lead the project today. Trilling put together an international team of solar system experts that includes researchers from France and Germany.

“This particular study started as a bunch of different solar system experts got together and thought about what would be a very good survey to launch with the Spitzer space telescope,” Penprase said. “They represent a cross-section of expertise in solar system work.”

One of these experts is Bidushi Bhattacharya, a professor at Caltech. She is also Penprase’s wife.

“She handles solar system stuff, and I handle things beyond the solar system,” Penprase said of the couple’s research interests.

Penprase, however, decided to explore new territory for this project.

“I don’t ordinarily work on solar system stuff,” he said. “But she thought I might be interested in this project, so I said ‘sure,’ as I often do when my wife invites me to do something.”

One of the main goals of the study is to form hypotheses about the origins of the NEOs. The team has produced three papers so far.

Members of the team attempt to gather data about the orbits, composition, and surface properties of these NEOs. They then analyze these data in order to learn more about the objects’ origins.

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