SciTech

Those stars above are probably still alive

Black stars! The words leaped out of an interview with singer Xenia Rubinos on National Public Radio’s Weekend Edition Sunday show, a couple of weeks ago. She was not speaking of the obscure astronomical object of that name, a theoretical condensed star, not to be confused with a black hole.

Rather, she was speaking metaphorically about her feelings for her song “Black Star” that had wrapped up concepts of Black Lives Matter, her last encounters with her dying father and an astronomical connection between these concepts.

As she told NPR, “I’d heard this thing about when you look up at the night sky, you might be looking at the light of the stars that no longer exist: that they’ve died, but their light is still shining. And I thought that was the perfect definition of what a black star is.”

The story she had heard is one that I get asked about frequently, especially at our public events at our Dark Sky Observatory: Is it possible that the stars I am seeing are no longer there?

The question arises from the finite speed of light and the enormous distances to the stars. The closest star you can see with the unaided eye from North Carolina, Sirius, is more than eight light-years away. So the light you see from Sirius left more than four years before it gets to your eyes. Vega, the bright star directly overhead at midnight, is 25 light-years away. The typical star you see in the night sky is tens to hundreds of light-years away, meaning that the light you see left the star decades to centuries ago.

Stars are not only enormously far away, but they also have enormous lifetimes. Even the hottest stars, which are relatively short-lived, live millions to tens of millions of years. More typical stars live billions of years. So it is extremely unlikely that they have died, yet they shine in your eyes. In fact, the predecessor stages to stellar death are generally understood, and we would likely know in advance they are on their way out. Mankind has only witnessed a few star deaths with the naked eye. We have our eyes on other aging stars now – old stars on deathwatch.

But those dead stars, in the form of neutron stars and black holes, are indeed dark. Yet, like Xenia’s thought suggests, their original light is still streaming outward, past us and onward indefinitely. They may still be visible to distant extraterrestrial beings who are still waiting to see those stars die. So, like those dark stars, like Xenia’s late father and like others lost from us, those lives still matter.

And, yes, that star you see tonight is probably still alive.

Daniel B. Caton is a physics and astronomy professor, and director of observatories at Appalachian State University. Email: catondb@appstate.edu. More on this month's column: www.upintheair.info.

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