Stargazing - 08.02.12
After the Sun, the first star whose distance was accurately measured was 61 Cygni.
It is part of Cygnus, the swan, which is high overhead this evening.
61 Cygni is fairly close to Deneb, the swan’s tail, and is about 11 light-years away.
Spinning Hearts
When we look at a star, all we see is the layer of gas at its surface. But astronomers would like to see a star’s core, because that’s where the action is. Nuclear reactions in the core convert lightweight elements to heavier ones, yielding energy — the energy that powers the star.
One way they can learn about the core is to look for ripples on a star’s surface. In fact, by using this technique, the Kepler spacecraft has shown that the cores of some giant stars are spinning much faster than their surfaces.
Kepler’s mission is to find Earth-like planets orbiting Sun-like stars. It stares at more than 150,000 stars in the constellations Cygnus and Lyra, monitoring their light for tiny dips that result when a planet passes in front of its star.
But the stars themselves also flicker. They vibrate, like a ringing bell, and Kepler is so sensitive to starlight that it can detect these vibrations. Mission scientists have converted some of those vibrations to sound. [SFX: Kepler audio]
The vibrations probe a star’s interior just as earthquakes probe Earth’s interior. Kepler observations of three giant stars indicate that their cores spin at least 10 times faster than their surfaces.
Billions of years from now, the Sun will swell to the same giant proportions as the stars that Kepler studied. And like those stars, the Sun’s core may spin much faster than its surface — producing flickers of light that will ripple through the galaxy.
