Star creations seen in new light

By Dan Shah

Astronomers at the University are better understanding the roles of gas and dust between stars as well as obtaining a better idea of the birth and death of stars by comparing images captured at different wavelengths.

The studies, conducted with x-ray, infrared, optical, radio and ultraviolet wavelengths, are showing different physical properties and processes that were never before really seen and also are helping to change old theories about the formation of stars.

Robert Gruendl, an astronomer and professor at the University, used an infrared telescope, known as Spitzer Space Telescope, to research massive stars and the way they interact with the interstellar medium, gas between the stars. The Spitzer Space Telescope is fairly new, only being used in the last two years.

“For a long time, people saw these star explosions as discrete (actions),” Gruendl said. “There isn’t quite the discrete production of stars. I think the main thing we are seeing is that past generations of stars are affecting present generations of stars forming. Some star formation produces more star formation and it propagates. It’s not a single event. It’s a continuous process.”

You-Hua Chu, University professor and the chair of the astronomy department, explains that infrared wavelengths are especially important for the types of stars that it shows.

“The infrared shows the newborn star,” said Chu. “These stars are formed from the collapse of another star. The dust is absorbed by a dust cocoon which is captured by infrared.”

The newborn stars are in the form of small dust cocoons that will be ionized and pushed out by the very dense gas being pressurized by the larger star, said Rosa Williams, professor and astronomer at the University.

The x-ray wavelengths are also especially important because they show the hot gas remnants from stars that have exploded.

This helped Williams’ find about star death. Traditionally, the thought was that the expanding shells of supernova remnants contained large amounts of gas and dust particles. Williams’ study shows that there might not be as much dust as originally thought.

“We know when a star has exploded, it is spitting out gas,” Williams said. “When we look at older ones we find that where we expected a lot of dust, we are not seeing a lot of dust. This is a surprise. There is not as much as we expected. Instead we are just seeing the gases we expected.”

Williams is currently looking into the reasoning to why there is not as much dust as expected. She believes that the high ultra-violet radiation can possibly break the gas apart. It is still a highly debatable issue she said.

“This is still a somewhat contentious issue whether this was really missing dust or not,” said Williams. “It is more difficult to detect.”

The importance of these studies will help us learn more about our galaxy since it is simple to observe from our current position.

“(Living in the Milky Way Galaxy) is like being in a pizza,” said Chu. “It is difficult to see what’s on top of the pizza and the topping on the pizza if you are in it. This is why we are studying other galaxies, to get an idea of ours. For example, looking all around us, we see x-rays, clueing us into being surrounded by hot gas.”

Chu said that there is now a complete optical survey of the Large Magellanic Cloud, a large and close neighboring galaxy that is often studied and which was discovered by Magellan.

Studying closer galaxies in high resolution with multi-wavelength images will lead to finding out more about galaxies that are further away, Gruendl explains. By studying conditions here with larger resolutions astronomers get a better idea of what’s going on, and can figure out how often star formation is going on and assemble a bigger picture of galaxies further away.

The astronomers presented their studies, which were funded by NASA, in Washington, D.C., on Jan. 11th at the American Astronomical Society meeting.