There’s something amiss in the night sky these days.

The evening is going well – I’m sitting by a crackling fire that I just used to clean a Dutch oven from our last trip out. (Something I actually neglected for about a week, just because I kept forgetting about it. I’ve learned that burnt molasses does not come out of a Dutch oven easily, but it came out more easily than I thought it would. The pie that caused this effort was definitely worth it, though….)

So as nice as tonight is shaping up to be, something’s wrong. We noticed last night, walking to a neighborhood New Year’s Eve get-together. Betelgeuse, the red supergiant star in what we see as the upper left shoulder of Orion, is much, much dimmer than it used to be. And of course I and my family are not the first to notice this. In fact, the astronomy community is talking about it a lot – over the past five months, Betelgeuse has gone from being the tenth brightest star in our sky to something like the 21st.

(I’d love to share a picture, but since most neighbors are still lighting up the place with Christmas lights, I can’t get a good “before and after” on the brightness – but I do have a “before” image, from about 2 years ago with the ISS streaking through.  Betelgeuse is the red star at left, about the same brightness as Rigel, the blue-white one to the right.  Go outside and look at the difference!)


We don’t know what this sudden dimming means. As I mentioned, the star is a red supergiant. If Betelgeuse was sitting in the place that our Sun is, the surface of the star would almost reach out to the orbit of Jupiter, and would be sending flares of material out almost as far as the orbit of Neptune. So it’s big, it’s luminous, it’s powerful. It’s fair to say that Betelgeuse is a huge star. In the grand scheme of things, it’s also one of our closest neighbors, at only 700 light years away. And for it to suddenly dim like this is a mystery, particularly to do it so dramatically over such a short period of time.

We do know that Betelgeuse dims periodically. It’s primary period is about 425 days, but there is an additional oscillation at a period of between 100-180 days, and another at 5.9 years. (There’s apparently a lot of things going on with this star). By one theory, this historic low – and by that I mean that Betelgeuse is currently dimmer than it has been since we started measuring it, about a hundred years ago – is simply the alignment of the various lows in these oscillations, just another cycle in in ancient star’s history. But, we can’t help but wonder, is Betelgeuse about to go supernova?

There are several astronomers that have suggested that we actually MAY be getting close to a supernova event. This would mean the explosion and death for one of the most well known stars in what is arguably the most well known constellation in our sky. If Betelgeuse were to go supernova, it would be as bright as the full moon, perhaps more, for several months. It would be visible in the daytime. Right now Orion is a night sky constellation, so if it exploded Betelgeuse would actually shine like a second sun, through most of the night. It would easily be bright enough to cast shadows on its own, like a full moon. Dramatic to say the least. And of course, as that glow dissipated, Orion would never look the same again.

Humanity has seen supernovae before. Every once in a while a bright new star suddenly appears in the night – and some of those we’ve been able to track (after the fact) for centuries. For example, the Crab Nebula is a remnant of a supernova, or “guest star” in the vernacular of the Chinese astronomers that documented it, that exploded in the year 1054. But most supernovae aren’t objects that we’ve been watching for a long time up before the critical event. And so, knowing what a star looks like just before it explodes is not something that we’re all accustomed to. We don’t really know the tell-tale signs that predict the death of a star – other than knowing that since Betelgeuse is already a supergiant, it’s definitely a candidate, eventually.


Layered multi-spectrum view of the Crab Nebula, remnant of the supernova from 1054, aptly named “SN 1054”.  Image from NASA.

So it’s possible, maybe even likely, that Betelgeuse is doing nothing. But maybe we’re in for a spectacular something in some period of time. Maybe tomorrow, maybe 1,000 years from now – We really have no idea, but it’s worth watching. It’s also a reminder that the universe is not a quiet, static place. People have been using the same star patterns for millennia to navigate, to tell stories of myth and legend to underscore human culture, and to suddenly have something like Orion be altered forever in a catastrophic event (well, to Betelgeuse it will be pretty catastrophic, the explosion won’t affect us at all) could be astounding.

If it did go supernova, we’d have a second sun for a while, and then that would fade out and likely leave behind a planetary nebula of some sort of expanding gas and debris, rushing out into space, backlit by electromagnetic radiation from the remaining neutron star. So it’s exciting. And it’s worth watching.

So with the possibility of significant alteration to our night sky LITERALLY hanging over your head, Happy New Year! I hope everybody has a great 2020 I hope you have substantial plans to guide your life forward in a positive direction. And I hope you take some time to look outside, be outside and ponder your place in the universe, even if the universe itself is subject to change.

Get Out There

7 thoughts on “Betelgeuse, Betelgeuse, Betel….

    • Neat idea, but no… Betelgeuse is far enough from the ecliptic that the Moon wouldn’t pass in front of it, but it would get close! The Moon occults nearby star Aldeberan pretty often – it would pass just north of a super-bright Betelgeuse. Cool thought!

      Liked by 1 person

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