You are here

More Moon and Companions

February 21, 2011

The Moon, the star Spica, and the planet Saturn arc across the sky late tonight like a celestial javelin. They rise in late evening, with Spica just above the Moon and brighter Saturn a little farther above Spica.

When we view these objects, we're seeing them in a thin band of the electromagnetic spectrum: visible light. But if we could tune our eyes up and down the spectrum, like changing stations on a radio, they'd look a lot different.

Saturn produces some radio waves, which are the longest wavelengths of energy, as charged particles from the Sun spiral through its magnetic field. It also emits a fair amount of infrared energy -- the result of heat radiating outward from its dense core.

As you go to shorter wavelengths, though, you'd see an even bigger difference.

In the ultraviolet, Spica would shine much brighter. That's because it consists of two stars, each of which is tens of thousands of degrees hotter than the Sun. Stars that are that hot emit most of their energy in the ultraviolet.

Spica's stars also produce strong "winds" of charged particles. The stars are so close together that their winds ram into each other like the spray from two firehoses. When they hit, they produce a lot of X-rays, making Spica one of the brightest objects in the X-ray sky.

By contrast, the Moon and Saturn produce almost no ultraviolet and X-ray energy. So at those wavelengths, Spica would outshine its two companions.


Script by Damond Benningfield, Copyright 2010


Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.