Florida Tech scientists earn NSF grant to study age of stars

Taking a unique approach

Florida Tech Scientists Earn NSF Grant to Measure the Age of Stars MELBOURNE, FLA.—Terry Oswalt, Ph.D., head of the Florida Tech Department of Physics and Space Sciences, has won a National Science Foundation grant of more than $380,000 for a unique approach to learning stars' ages.

"How old is it? Is just about the most difficult question you can ask about a star," said Oswalt. He and his team will determine ages by studying the chromospheres, or outer atmospheres, of stars like the Sun. Chromospheric activity, like sunspots and the solar cycle, is known to correlate with age but the exact relation has not been explored beyond the age of the Sun.

"Stars, like people, become less active as they age. We're looking at stars like our Sun across a wide range of ages to see exactly how the faint features in their spectra, which are markers for activity, weaken with age," said Oswalt.

Oswalt is taking a new approach to calibrating and extending this age determination technique. He has selected a sample of stars like the Sun that happen to have "dead" companion stars known as white dwarfs. White dwarfs are the cooling embers of stars that have run out of fuel and are slowly cooling over time.

"Much as the coroner at a crime scene gauges the time of death by taking the victim's temperature, we get the so-called 'cooling age' of a white dwarf by taking its temperature," said Oswalt. This provides an independent check on the companion star's age, because stars in a pair were born at the same time. Using white dwarfs, which tend to be very old, Oswalt may be able to extend the activity-age relation for solar-type stars right up to the age of our galaxy, the Milky Way, about 10 billion years.