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UD astrophysicist uses the Hubble Telescope to observe dying stars

NASA and H. Richer (University of British Columbia)
Ancient white dwarfs in the Milky Way

Last Friday, the Hubble Space Telescope celebrated its 25th anniversary.

During its time in space, the Hubble has sent back to Earth stunning images of outer space and helped astronomers make significant discoveries that can’t be accomplished with telescopes on the ground.

For astronomers, booking time with the Hubble Space Telescope can be a lot like trying to reserve a table a Michelin starred restaurant. Judi Provencal, an astronomer at University of Delaware, has used the Hubble to study white dwarfs, also known as dying stars.


"It’s kind of like forensic astronomy, digging around in the guts of theses dead stars, trying to find out what they ate for lunch," said Provencal.


White dwarfs are relatively warm objects, ranging from 20,000 to 30,000 thousand kelvins. Kelvins, by the way, is a unit of measure for temperature that's often used with objects in outer space. Our own sun is around 5,000 kelvins. Knowing how hot these dead stars are can help determine their make-up, how quickly they process energy and even help estimate the age of its galaxy.

Provencal studies pulsating white dwarfs, which change brightness over time. These pulsations allow her to learn more about them.

“If you ring a bell, it makes a certain noise,” said Provencal. “Imagine having a row of bell ringers, and everybody has a bell with a different tone. The tone comes from the shape of the bell or from the metal that the bell is made of. Stars in general do the same thing -- how they pulsate, how they ring depend on what they’re made of inside.”

Provencal is trying to understand how exactly stars decompose and process energy, which could indicate how the future of our sun might unfold. An important part of this research depends on how well the telescope can detect a white dwarf’s temperature. A ground-based telescope could be off by a few thousand degrees, while the Hubble telescope could capture the temperature within 200.

The Hubble telescope can see in the ultraviolet range in the electromagnetic spectrum, helping astronomers like Provencal who observe hot celestial objects like white dwarfs. However, the Hubble’s successor - the James Webb Telescope that will be launched in 2018 - sees in infrared, which is better for cooler objects, like exoplanets. Provencal is hopeful funding will be found to put another ultraviolet telescope in space.

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