Ability to see stars slowly disappearing


By Tom Burns - Stargazing



We are 22 years into the new millennium, and I am finally, at my wife’s insistence, beginning to clean out the 20th century detritus from my home office. In doing so, I discovered an old newspaper clipping from USA Today that I can’t bring myself to discard.

As the millennium turned, they surveyed people about what they particularly loved in the 20th century and will miss in the 21st. I regretfully report that “the stars” were near the top of the list.

The stars are going away. The glow of urban security lights provides no security. Brightly lit billboards and glare-producing streetlights increasingly befoul rural areas.

There will come a time in the current century when the old constellations are invisible except in small enclaves in the western United States.

That is one of the great ironies of our century. As we finally begin to understand the universe’s form and function more thoroughly, we are losing 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. Go to a Friday night program at Perkins Observatory as soon as possible.

Avail yourself of the John Glenn Astronomy Park (JGAP, for short) in Hocking Hills State Park, one of the few public stargazing locales in Ohio where the night sky is still decently dark and starry.

Join the Columbus Astronomical Society for access to their dark-sky observing sites.

An excellent 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.

The mythologies of many ancient cultures feature the stars of Cepheus. The constellation 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 character weakness so great that he was willing to sacrifice his daughter to the jaws of Cetus, the Sea Monster, which was ravaging his kingdom’s coast 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 designation for Cepheus, but earlier Arabs called the constellation Al Aghnam (“The Sheep” in English).

The change of designation created an odd mixture of stellar names. The brightest star of the constellation is 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. Alrai, “The Shepherd” watching over the flock, marks the peak of the king’s dunce cap.

Those stars aren’t much to look at. However, buried in the constellation is a true gem, barely visible to the unaided eye from our ever-decreasing dark, rural skies. (You can still see it with the unaided eye at Perkins, barely.)

Above and halfway between the top two stars of the constellation is the Garnet Star. It looks as if the upside-down Cepheus is wearing a garnet necklace.

As the name suggests, the Garnet Star is red. In effect, it’s the reddest star visible to the unaided eye.

The star owes its name to 16th century astronomer William Herschel, not because he discovered it, but because he was the first telescopist to note its “very fine deep garnet colour.”

Binoculars or a small telescope show its redness the best. The star looks increasingly orange in larger and larger telescopes, and it appears distinctly yellow-orange in an observatory-sized telescope like the one at Perkins.

You’ll get your best views of it in smaller telescopes set up on the lawn by the Columbus Astronomical Society. Ask one of them to show it to you.

The star’s color tells us much about it. The Garnet Star is a red hypergiant, a massive star that has reached a premature old age. The star’s condition is similar 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. 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 with the mass of our sun fuse hydrogen into helium in a hydrogen-bomb explosion that can last billions of years.

However, the Garnet star started with a mass of 20-25 times that of our sun. Such stars expend their hydrogen very quickly. The star is now fusing its helium into carbon and its carbon into iron.

Like most hypergiants of its kind, the Garnet Star’s old age is premature. At only 10 million years old, the star has consumed its hydrogen fuel like a ravenous giant.

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

As stars like the Garnet reach extreme old age, they begin to pulsate, growing larger then smaller, brighter then dimmer, then back again.

Astronomers have kept careful records of the Garnet Star’s pulsations since English astronomer John Russell Hind discovered its variability in 1848.

The Garnet Star belongs to a class that astronomers call semiregular variables. It has pulsations within its pulsations. Thus, astronomers have measured periods of variability lasting both 860 days and 4,400 days.

Such stable instability (or is it unstable stability?) is what one might expect from a star in the throes of stellar decrepitude.

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 people like me make such nuisances of ourselves harping about light pollution, go to a public stargazing session and see its scarlet splendor while we still have the chance.

Or travel to those 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 twenty-second century, their children will stand against the sodden, gray background of a sky they have never seen and tell their children how glorious it used to be.

To learn about John Glenn Astronomy Park public programs, visit https://jgap.info/.

For Perkins Observatory, see https://www.owu.edu/about/offices-services-directory/perkins-observatory/.

https://www.delgazette.com/wp-content/uploads/sites/40/2022/08/web1_Burns-3.jpg

By Tom Burns

Stargazing

Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.