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Moon and Regulus

June 8, 2019

There’s a graphical code for just about everything. The barcode on a can of beans, for example, contains information about the product and its price. And QR codes on ads send you to web pages with a longer sales pitch.

The stars come with their own graphic codes. And over the last century and a half, astronomers have developed ever-better “scanners” for reading them.

The scanners are spectroscopes. They break the light from a star into its individual wavelengths or colors. The intensity of light at each wavelength reveals important details about the star.

Consider Regulus, the bright heart of Leo, the lion. The star is quite close to the lower right of the Moon this evening.

Spectroscopy tells us that the surface of the bright star we see as Regulus is thousands of degrees hotter than the Sun. It tells us that the star is made mainly of hydrogen and helium, with smatterings of other elements. And it helps reveal that the star spins must faster than the Sun does.

Perhaps most important, it reveals a companion star that’s too close and faint to see through the glare of the bright star. It probably is a white dwarf — the corpse of a star that once was much brighter and bigger.

The discovery of the white dwarf told astronomers that the system is older than they’d thought. And it helped them deduce that the bright star has changed over time as it interacted with the companion — a companion with its own stellar code.

Script by Damond Benningfield

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