A star in the constellation Orion is dimmer than it has been in 100 years
Hi again, welcome back to Plain English, the best podcast for learning English. I’m Jeff and JR is the producer. This is episode 222 and you can find the full transcript of this program at PlainEnglish.com/222.
Coming up today: Betelgeuse, a red supergiant star that makes up Orion’s shoulder, is dimmer than it has been in 100 years. By the way, “dim” is the opposite of bright. And stars of this type tend to lose their brightness right before they explode. So is that about to happen? Is Orion about to lose his shoulder? That’s what we’ll explore in the first part of today’s episode. In the second half, we’ll talk about the expression “ebb and flow,” and JR has a song of the week.
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Is a supernova on the horizon?
Life changes quickly down on Earth, so sometimes it’s comforting to know that if you look up at the night sky, the familiar patterns of the heavens are unchanging. Whatever is going on down here, we’re just a speck in the universe. The night sky is will always follow the same patterns, show us the same stars, remind us of our fixed position among the celestial bodies.
Except it’s not really that way. Our lives are so short, relatively speaking, that we don’t live to witness big changes in the universe. And those of us without telescopes can only see just a little bit of the universe anyway. But every now and then, there is a visible change in the night sky that reminds us of the changes happening far, far away.
One of those changes may be happening now. If you’re like me, you probably learned about the constellation Orion. It is among the three most-recognizable constellations, named after a hunter in Greek mythology. It is visible from every part of the world and is clearest from January to March.
One of its stars, called Betelgeuse, is the dimmest it has been in almost a hundred years. The star is the second-brightest in the constellation and is typically the ninth-brightest star in the sky. But in October, it started dimming. By last month, it wasn’t even in the top twenty brightest stars in the sky.
Not all stars are equally bright all the time; a variable star is one whose brightness ebbs and flows, and Betelgeuse is known to be this kind of a star. But the reduction in its brightness is such that astronomers are starting to wonder if something big might be about to happen. Perhaps it’s more accurate to say that astronomers wonder if we’re about to see something happen. After all, if something happens on Betelgeuse, we wouldn’t see it until 600 years later.
What might happen? Betelgeuse is a red supergiant. That means it’s large in terms of volume—if it were in the place of the sun, it would be so big that the Earth would be inside it. But it’s not large in terms of mass. Compared to other stars, the surface is relatively cool. These stars live short but tumultuous lives. Betelgeuse is about 8.5 million years old—relatively young for a star—but is nearing the end of its life. It will die in a massive explosion called a supernova, the result of a series of nuclear reactions.
If that happens to Betelgeuse, the supernova would be visible from earth. For a short period of time, it would be brighter than the moon and would be visible during the day. After that, it would be gone—all its mass pushed out into the rest of the universe—and Orion would be without a shoulder.
Is that about to happen? It’s impossible to know. Betelgeuse tends to follow patterns of brightness. One longer-term pattern repeats about every six years. Another shorter pattern repeats every 425 days. This could simply be a more pronounced example of the star’s normal variation. One astronomer says this is nothing special: he says that the star happens to be at its dimmest point in both its cycles, making it appear especially dim.
Chances are that Orion will remain intact for all of our lifetimes. Scientists think that the star will explode in the next million years—and perhaps in the next ten thousand years. But there’s a small chance we’ll see it. The most recent supernova to be visible from earth was in 1604, named after the German astronomer Johannes Kepler. It was visible during the day for over three weeks and descriptions of it appear in European, Chinese, Korean, and Arabic texts.
I learned about astronomy as a kid and I remember looking up at the sky and not seeing anything. The Big Dipper, sure. The Little Dipper, all right. But I didn’t see a hunter. Orion is a hunter. I didn’t see a hunter. I certainly didn’t see a ram (Aries), a queen (Cassiopeia), twins (Gemini), or a lion (Leo). I remember looking up and seeing a jumbled mass of stars and grown-ups trying to convince me that if you looked just right, at the right combination of stars, then you could see these figures. I just didn’t get it. Perhaps it was their relationship to Greek mythology. I absolutely hated Greek mythology as a kid, and maybe that spoiled the constellations for me. Who knows.
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