Cepheus and the Garnet Star


Tom Burns - Stargazing



We are now 16 years into the new millennium, and my thoughts turn to an old newspaper clipping from USA Today. As the millennium turned, they discussed the things that people said they particularly loved in the twentieth century and will miss in the 21st. Sadly, the stars were near the top of the list.

The stars are going away. The glow of security lights that provide no security, brightly lit billboards, and glare-producing streetlights increasingly befouls rural areas. There will come a time in the 21st century when the old constellations are invisible except for small enclaves in the western United States.

That is one of the great ironies of our century. As we have finally come to understand more fully the workings of the universe, we have lost the ability to see it with our own two eyes. Like many other aspects of nature, our experience of the universe has now become filtered through glowing screens.

We must make the best of a bad situation while we can. A good place to start is the now-obscure constellation Cepheus, the King, and a single star in it, the gloriously red point of light called the Garnet Star.

Cepheus is featured in the mythologies of many ancient cultures. It is sadly unfamiliar to most people these days because its relatively faint stars barely shine through the glow of urban nighttime lighting.

The constellation goes back at least to the Chaldeans of 2300 BCE. To the later Greeks and Romans, Cepheus, king of the Ethiopians, was father to Andromeda, a constellation to the east and husband to Cassiopeia to the northeast.

He is best known for a weakness of character so great that he was willing to sacrifice his own daughter to the jaws of Cetus, the Sea Monster, who happened to be ravaging the coast of his kingdom at the time.

To our modern eyes, Cepheus looks like a head wearing a well-deserved dunce cap.

His fitting punishment for his crime against his daughter is that he spends most of the year hanging upside down.

The ancient Arabs named the brighter stars of the constellations, and we still use those names. They eventually accepted the Greek name for Cepheus, but earlier Arabs called the constellation Al Aghnam, “The Sheep.”

The change of designation created an interesting mixture of stellar names. The brightest star of the constellation is called Alderamin, a western corruption of the Arab Al Dira al Yamin, “The Right Arm,” presumably of the king. The second-brightest star is Alfirk, “The Flock,” presumably of sheep. Marking the peak of the dunce cap is Alrai, “The Shepherd” watching over the flock.

Those stars aren’t much to look at. However, buried in the constellation is a true gem, just visible to the unaided eye from our ever-decreasing dark, rural skies. (We can still see it with the unaided eye at Perkins, barely.) Above and half way between the top two stars of the constellation is the Garnet Star.

As the name suggests, the Garnet Star is red. In fact, it’s the reddest star visible to the unaided eye. Binoculars or a small telescope show its redness the best. The star looks increasingly orange in larger and larger telescopes, and it looks distinctly yellow-orange in an observatory-sized telescope like the one at Perkins. We get our best views of it in smaller telescopes set up on the lawn by the Columbus Astronomical Society.

The star’s color tells us much about it. The Garnet Star is a red supergiant, an enormous star that has now reached a premature old age in a similar way to the more famous Betelgeuse in the constellation Orion.

Stars cool down considerably when they reach their decrepitude. The Garnet star is a rather tepid 6,000 degrees Fahrenheit. That fact doesn’t stop it from shining a startling 283,000 times brighter than the sun.

Stars tend to puff up when they reach old age. The Garnet Star is well over 1,000 the diameter of the sun, large enough that if the sun were removed from our solar system and replaced with the Garnet Star, Earth would be well inside the star. In fact, the star would engulf Jupiter and make it part of the way to Saturn.

It will not remain that way for long. In their long youth and middle age, stars fuse hydrogen into helium in a hydrogen-bomb explosion that can last billions of years. Stars like the Garnet Star expend their hydrogen very quickly. The star is now fusing its helium into carbon and its carbon into iron.

In a few million years, the Garnet Star’s hydrogen-bomb reaction will cease, the star’s core will collapse to a black hole, and its outer shell will expand explosively in a supernova explosion that will light up Earth’s distant sky.

Most stars don’t show their colors very well to human eyes. That makes the Garnet Star extraordinarily beautiful and rare. If you want to know why we make such nuisances of ourselves harping about the light pollution around Perkins Observatory, come to one of our public programs, and we’ll show you its scarlet splendor while we still have the chance.

Or travel to those wondrous and rare rural locations in southern Ohio where the stars still shine like diamond dust against the uncorrupted blackness of the sky. Let your children and grandchildren see the beauty of the universe in which they live. Perhaps at the turn of the 22nd century, their children will stand against the sodden, gray background of a sky they have never truly seen and tell their children how glorious it used to be.

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Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.

Tom Burns is director of the Perkins Observatory in Delaware.