VU researchers to study white dwarf stars with the Hubble telescope – Chicago Tribune

Valparaiso University Professor of Physics and Astronomy Todd Hillwig, Ph.D., is the sole American researcher involved in an international project using the Hubble Space Telescope to learn more about the universe. Hillwig received a $72,743 grant that will fund the hiring of student researchers who will help study dwarf white stars over the next three summers.

Titled “A Treasury FUV Survey of the Hottest White Dwarfs,” the project is special because it’s part of a Treasury Program. Typically when researchers use the Hubble Telescope the information they glean from it remains proprietary for 18 months. With a Treasury Program, however, as soon as collected data is archived it is downloaded for sharing amongst the scientific community.

For this reason the white dwarf research was granted 130 orbits of time with the Hubble. Typically, research projects are only granted 10 orbits. It takes the Hubble 90 minutes to orbit the earth.

The project is an international effort run through the Space Science Telescope Institute. Nicole Reindl, Ph.D., at the University of Potsdam, Germany, is the lead researcher of the group of 17 scientists that will be analyzing white dwarfs — stars at the end of their life cycle.

A dwarf star can be defined as any star less than eight times the mass of the sun. Toward the end of its life this type of star becomes smaller, but is extremely dense because of its crystalline structure of mostly carbon and oxygen.

White dwarfs are commonly the size of earth, but difficult to see in space because they don’t give off much light, though they are very hot. VU students will assist in analyzing spectra from the white dwarfs, or measuring how bright the star is at many different wavelengths. “It turns out studying spectra of these stars in light we see is complicated,” Hillwig said.

The Hubble Telescope is key because it can measure ultraviolet light coming off the stars that telescopes on earth cannot due to the earth’s atmosphere absorbing UV light. Telescopes on earth in Chile, the Canary Islands, and Arizona, part of the Southeastern Association for Research in Astronomy which VU joined in 2006, will be used for supplementary research however.

Hillwig said a teaspoon of white dwarf matter would weigh many tons on earth. There are other trace elements besides carbon and oxygen in their makeup. Identifying these is a part of the project. “They make a really big difference in how hot it can be,” Hillwig said of the trace elements.

Hillwig’s group will be focusing on the 100 hottest white dwarfs identified in the universe. “There are difficulties in understanding those that don’t exist for the cooler ones,” he said.

When it enters the white dwarf stage, a star begins to shrink and cool and will stay in this phase until it dies. This can happen by continued cooling, or, of particular interest to Hillwig’s study, the inevitable can be put off a little longer.

Some white dwarfs are binary stars, part of a pair of stars in which a white dwarf is orbited by another star not yet in decline. The white dwarf, in a cannibalistic move absorbs the orbiting star in a fashion Hillwig described as “shredding it” and takes on its mass before exploding as a supernova.

The light from these supernovae can be used as a sort of pinpoint to help in determining the size of the universe.

The sun will eventually become a white dwarf in its end stage and is expected to last to around nine billion years of age. It is currently four-and-a-half-billion years old.

VU offers an astronomy major, which is a combination of both physics and astronomy courses, as astronomy is a subfield of physics. VU astronomy students will be paid with the grant funding to assist in research over the next three summers.

“We try to hire students here every summer. It’s a big part of our department,” Hillwig said. “The goal is to get as many of our students as possible that kind of experience.”

Shelley Jones is a freelance reporter for the Post-Tribune.