It’s been an exciting week for extra-terrestrials.
And we’re not talking about Little Green Men here.
The news was fairly crowded with reports of the asteroid that missed Earth by a cosmic hair, and the space rock that provided a rude awakening to Russian city by not missing it.
The two events are entirely unrelated; the trajectories of those bodies were so different they literally came from different neighborhoods in space. Still, space rock No. 2 provided a reminder of what could happen — on a much larger scale — if something like the asteroid would hit us. Clearly, more than a few windows would get broken!
And what do you know — the Kepler space telescope, our friendly planet hunter “out there,” has found interesting space rocks, too: tiny planets orbiting faraway stars. One of them is only slightly larger than our own moon.
A few years ago this kind of discovery was unheard of. With the capabilities of the telescopes then it was only possible to find very large planets orbiting other stars. We’ve looked at Kepler’s technique before: the telescope’s unblinking eye stares at a bunch of distant stars and measures the tiniest dips in brightness. If a dip is detected it is logged and compared to other data on the same star to see if those dips occur regularly, which means there’s a pretty good chance a planet is responsible for those changes.
But Kepler is also far more sophisticated than that. In order to determine the size of a planet orbiting a star one has to know the size of the star first. Scientists did that by examining the sound waves the boiling motion below the surface of a star generates.
But wait a second, you might say, how can you possibly hear the noise a star makes? Don’t you need air for the sound waves to travel to your ear? Well, no. In this case the sound waves travel into the star and are reflected back out, and they show up as a rapid flickering on the star’s surface. That’s something you can measure in a field of science called astroseismology — literally “starquakes.”
Smaller stars pulse very rapidly in higher frequencies whereas bigger stars boom more slowly in lower tones, and of course there’s a direct correlation between tone and size. And there you have it: the size of the star! And with that you can calculate the size of the planet you’ve just discovered.
It’s really quite amazing, when you stop to think about it; after all, none of these planets have ever actually been seen — only their effects on their stars.
That’s some might fine cosmic sleuthing there, Sherlock Kepler!
Learn more about Kepler’s adventures at http://kepler.nasa.gov/
Beate Czogalla is the Professor of Theater Design in the Department of Theatre and Dance at Georgia College & State University. She has had a lifelong interest in space exploration and has been a Solar System Ambassador for the Jet Propulsion Laboratory/ NASA for many years. She can be reached at firstname.lastname@example.org