Blaze Star flares to great brilliance


By Tom Burns - Stargazing



It’s amazing how astronomy leaks over into popular culture. Movies like 2014’s “Interstellar” make a serious effort to apply complex ideas like wormholes and warped spacetime to human experience. For those movies, an old stargazer like me is forever grateful.

Sometimes the astronomical references are obscure, to say the least, and only an old stargazer might notice them.

A recent trip outside at about midnight is a case in point. The constellation Corona Borealis was rising in the east just above the more familiar star grouping that represents the ancient hero Hercules. Corona is worth a look in its own right, and I probably ought to write about it sometime. However, the only thoughts that came to mind concerned “Blaze,” a 1989 movie about a romantic relationship between Earl Long, former governor of Louisiana, and a stripper — er, exotic dancer — named Blaze Starr.

Starr may have taken her stage name from a famous star in the constellation Corona Borealis.

It doesn’t look like much now. You’ll need binoculars to see it. But, every 80 years or so we witness the rising of the star T Coronae as it blazes to well above naked-eye visibility.

During the evening of May 12, 1866, stargazers were shocked to see a naked-eye star where one had not been before.

The new star faded rapidly. In only eight days, it had sunk below naked-eye visibility.

“T” turned out to be a special kind of star called a nova, or “new star,” which unexpectedly flares to brief brilliance.

In its normal state, “T” shines 50 times brighter than our sun. At its maximum luminosity. it shines as bright as 200,000 suns!

British astronomer William Huggins immediately applied the new science of spectroscopic analysis to the star. He split the light from the star into its component parts, much like a prism divides sunlight into its rainbow colors. This rainbow is called the spectrum of the star.

Huggins discovered that a stellar explosion caused T Coronae’s brief brightness. He also was somewhat surprised to find a second spectrum instead of just one.

Modern astronomers believe that the secondary spectrum indicates that a rapidly expanding shell of gas surrounds “T.” The star apparently was blowing off its outer layers at a speed of nearly one million miles per hour, a velocity virtually unparalleled in our galaxy.

There the story temporarily ends. However, 80 years later, the Blaze Star, as it came to be known, did it again!

In February 1946, “T” again flared to great brilliance, making it what is called a “recurrent nova.” In 2016, astronomers began to see the telltale signs of another outburst. Thus, the star probably will make a return engagement in 2026, so mark that year on your calendar.

Further spectroscopic analysis suggests it is really two stars. The main star is a red giant 120 times the diameter of our sun.

It has a tiny blue-white dwarf circling around it. The dwarf is apparently what’s causing all the trouble here. It has about two-thirds the “starstuff” of its much larger companion. Yet, its material is packed down to a size that may be no greater than a planet like Earth.

That fact makes it incredibly dense. A tablespoon of it might weigh several tons. Its extreme density gives it the gravitational power of a normal star, except that its gravity is compressed into a very small space. Its density also makes it very hot, hotter than our sun, and much hotter than its companion.

The red giant is much more spread out. Its outer layers are so thin that they are barely there at all.

The dwarf orbits the giant so closely that it passes within the thin outer region of the red star, bumping and grinding its way against the tenuous “surface” of the red giant.

Astronomers aren’t sure what causes stars like the Blaze to pulsate periodically.

One theory holds that as the dwarf circles around its larger companion, it sucks the substance of the red giant into orbit around itself. Thus, some portion of the red giant’s material is probably pulled onto the extremely hot surface of the dwarf.

Eventually, enough material builds up on the surface to fuel a massive explosion.

Another theory suggests that the blue-white dwarf strips the red giant of its outer shell, laying bare the hot layers underneath. What we see during an explosion is the rapid expansion of the red star and the consequent exposure of its brilliant inner regions. The white dwarf’s high gravity causes the explosion, but the dwarf does not explode.

But that scientific controversy pales when compared with an even greater mystery that has yet to be resolved.

Did Blaze Starr the dancer open up a newspaper one fateful day in 1946 and read about the latest eruption of T Coronae? Did she decide to take her stage name from the star?

Or did the astronomer who gave the star its nickname have a secret obsession with exotic dancers?

This old stargazer promises his loyal readership one thing. He will not rest until he finds the answer.

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By Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.

Tom Burns is director of the Perkins Observatory in Delaware.