When many people see an exploded star, it’s because they’re watching the newest science-fiction film.

However, when Edward Baron, physics and astronomy professor, sees an exploded star, he sees a ruler to measure the universe with, and he’ll talk about why 7 p.m. Thursday during his lecture “Measuring Distance with Supernovae” at the Sam Noble Oklahoma Museum of Natural History.

A supernova is, “a star that blows up,” Baron said.

There are two types of supernovae, Baron said. Type 1A happens to solar systems with two smaller stars orbiting close to each other. Because these stars are not hot enough to burn carbon, when one of the stars goes out it leaves a planet-sized core of carbon, called a white dwarf, Baron said.

“When [the still active star] starts to get ready to slough off its material, it will puff up and it will start dumping material onto that white dwarf cinder,” Baron said.

When that white dwarf absorbs enough material to reach a certain size, it becomes what’s called a standard candle, Baron said.

These standard candles are what theorists like Baron use to determine the distance to other parts of the universe, he said.

Scientists use the standard candle’s absolute brightness (how bright it actually is) and its apparent brightness (how bright it seems from the Earth) to determine how far away the star is, Baron said.

The other more common type of supernova, which happens to massive stars, isn’t helpful in measuring interstellar distances, but is useful to the universe.

Massive stars are stars at least eight times larger than our sun, with cores hot enough to burn carbon. This means that when a supernova happens, elements are distributed across the universe, Baron said.

“[The massive star] dumps the gas into the interstellar medium and then it gets incorporated in planets, new stars and people,” Baron said.

This distribution of elements is very good for planets like ours, but it doesn’t help scientists determine distances to other stars, Baron said.

Baron’s lecture is part of a series of celebrating the 400-year anniversary of Galileo inventing the telescope, Richard Henry, physics and astronomy professor, said.

The series is sponsored by the OU Homer L. Dodge Department of Physics and Astronomy, The Sam Noble Oklahoma Museum of Natural History, Norman Public Schools, the Oklahoma City Astronomy Club, Odyssey Astronomy Club, Ten Acre Observatory, Astronomics and R.A. Graphix, according to the International Year of Astronomy 2009 Web site.

An opportunity to observe celestial objects through telescopes will follow the lecture, Henry said.

Organizers advise those wishing to attend to show up early because there is limited seating.

“It does fill up pretty fast,” Henry said. “We even had big crowds over the summer.”