Wednesday, July 02, 2014

Podcast: Dark Stars and Cosmic Cocktails

Image: Princeton Press
In Katherine Freese's new book The Cosmic Cocktail: Three Parts Dark Matter, she traces the history of dark matter and her career as an astrophysicist navigating through it.

For the last few years, she's been developing her theory of dark stars, giant primordial stars powered by dark matter annihilations, which she talks about in this week's podcast. Most recently she and her fellow researchers have been probing whether they are not only bright and gigantic, but also if they pulsate.

Certain kinds of stars, called Cepheids, expand and contract regularly in a cycle of heating and cooling. As they heat up, they expand out until they're so big they start cooling down and contracting again. On Earth it looks like they're getting brighter and dimmer over time. The length of their cycle depends on their average luminosity. Knowing their absolute brightness means that scientists can tell how far away they are by gauging how dim they appear. They're used as the standard rulers to determine how far away other galaxies are.

Freese has been performing calculations to determine whether dark stars might also pulsate. If that's the case and they're discovered in the far-off universe, they could be another tool for astronomers to more precisely determine the distance from here to the most distant galaxies.

The Hubble Ultra-Deep Field, the most distant galaxies at the very edge of the visible universe.
Image: NASA

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