Supernova over the Pyramids in the Far Future

I’ve been thinking up one of my capricious little vibes: the Great Pyramids at Giza, far into the future, long since restored to their original glory in pristine blinding-white limestone, all the artifacts and the mummies now house in museums returned to their tombs, the city of Cairo no more as the human population empties out into the countryside and into outer space, a rewilded Earth where the skies are once again totally dark over mankind’s first truly great monuments.

Already evocative enough. When to set this little caprice? At first I was thinking the first “quadruple-leaping year” of my Cosmic Standard Calendar, 1,650,000 years after the turn of its epoch (the year of American independence). See more about my calendrical worldbuilding here. That would be the year 1,651,776 CE; or 1,649,753 years from now.

That’s a long time, but the Pyramids will almost certainly still be there. Mankind in my universe’s timeline gradually scatters to the wind, abandoning Earth to Mother Nature, but the greatest of monumental structures are the last to be abandoned; it will take thousands, even millions, of years before humanity stops caring about them.

Even after that happens, consider that Mount Rushmore, among the most durable of all our structures, will remain recognizable for up to 7 million years after maintenance ceases. Kenneth Emery in 1960 estimated the Great Pyramid at Giza would remain standing for 100,000 years or so without maintenance.

It’s my understanding that the original white-limestone cap protected it from weathering, and many Egyptian monuments were also protected by being largely buried under sand dunes that had accumulated over the millennia; if the protective caps were restored and dunes grew around the Great Pyramids at Giza, they may well last for much longer than Emery’s figure even without any maintenance work.

Anyway, these monuments are like mountains: come the first quadruple leaping year, they’ll still be there. Precious little else of man’s handiwork will be, but they’ll stand like sentinels in an otherwise wild planet, the pharaohs’ artifacts crying out to the universe “Man was here!”.

Might the universe cry back?

I’ve been thinking that this general period of time is roughly the era in which the most hotly anticipated of all yet-to-come great supernovas will take place: the explosion of Betelgeuse. When exactly Betelgeuse will explode remains mysterious; in recent years a study that claimed a supernova might be imminent in the 21st century made a splash, but generally scientific assessments give estimates on the order of 100,000 years, though it could be substantially shorter or substantially longer. Maybe even long enough to keep the star burning brightly in the Earth’s sky for another million years hence…

Interestingly, while constellations will generally be unrecognizable then, due to the different proper motions of the stars taking them out of the patterns we’re familiar with, Orion will be among the last of our familiar constellations to succumb to the process, on account of all of its brightest stars being relatively distant (and slow-moving as seen from Earth). Orion’s belt, especially, will look only somewhat different from its current alignment one million years hence. Betelgeuse, alas, has much higher proper motion than the belt’s stars, so it will be well out of alignment by that point, so the whole constellation won’t be the same then (source).

Nevertheless, it’ll still be among the brightest stars as seen from Earth. When it explodes, it’ll become far brighter. Predictions are its supernova will shine roughly as bright as the full moon. That’s pretty bright; easily enough to be seen in the daytime sky, and to light up those pristine pyramids’ facades in a blinding white at night. Interestingly, the brightness is expected to be relatively constant for 2 to 3 months before starting to dim.

Eventually Betelgeuse’s remnant will be a neutron star of perhaps 1.5 solar masses, along with a surrounding nebula comparable to the Crab Nebula, which is the remnant of a supernova that took place in 1054. Considering the Crab Nebula’s apparent magnitude is 8, not too far beyond the naked-eye limit of magnitude 6, and that it’s 10 times further away, it seems likely that Betelgeuse’s supernova remnant will be easily visible with the naked eye long after the supernova itself expires.

At least according to Google Bard the Crab Nebula won’t dissipate for another 100,000 years, so for all I know a broadly similar lifetime should be expected for Betelgeuse’s nebular supernova remnant.

Admittedly all this is a little bit speculative, but I can’t readily find very many good sources on the topic, and my suppositions do seem reasonable. So imagine some lone protagonist coming in from far off in space to the ancestral homeworld, making a pilgrimage to the land of the pharaohs, incomparably more ancient to her than it is even to us, then…she has the privilege of seeing, in the night sky over those monuments, a new star as brilliant as the full moon suddenly shine forth, lighting up the dunescape all around her.

So evocative it makes my spirit vibrate with the music of the spheres just thinking about it. Might make great fodder for a short story sometime…

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