With a supermoon and a comet, things are looking up for aurora-less Philly skywatchers

In what has been quite the week for night-sky connoisseurs, the promised comet that is a fragment of the origins of our solar system has been appearing in the western sky after sunset, and looks to remain in sight for at least the next several days.

And it’s about to share space with a “supermoon,” which will be rising on the opposite side of the sky, appearing noticeably brighter and larger than the average full moon, since this one will mark the closest approach of the year.

While you should have no trouble seeing the moon with the naked eye, comet C/2023 A3 Tsuchinshan-ATLAS may take a little more effort, which its fans say would be worth the trouble.

In real life, the cometic materials may seem like a prosaic mix of rock and ice, but “these are the original building blocks of the solar system,” said Edward Sion, professor of astronomy and astrophysics at Villanova University. Besides, this thing appears only once every 80,000 years.

Clouds and light interference permitting, the comet will be visible almost due west after sunset, at about a 16-degree angle above the horizon, on Wednesday night, NASA says.

As the Earth turns, the comet slowly will sink toward the southwest, said Derrick Pitts, astronomer at the Franklin Institute. He recommends viewing it with binoculars, although it can be seen with the naked eye.

“Comets look even more dazzling through binoculars or a small telescope,” agreed Bennett A. Maruca, astronomy and physics professor at the University of Delaware. “The gas and dust that surrounds comets gives them a ‘fuzzy’ appearance. Indeed, the word comet derives from the Latin word for ‘hairy.’”

William J. Cooke, lead of the NASA Meteoroid Environments Office in Huntsville, Ala., said the comet “should remain visible to the unaided eye for about another week to 10 days.” He said that even with his “bad eyes” he was able to see it above a lighted parking lot.

But he added: “It’s fading fast, so folks should take a look while they can.”

While the comet will be climbing higher each night, it also will be losing brightness, said Pitts.

“It will drop below naked-eye visibility by the end of the month,” he said.

Said Cooke, “C/2023 A3 may not fit the definition of a great comet, but it is most certainly a pretty good one.”

Unlike with the comet, you won’t have to wait 80,000 years for another shot at seeing the full moon, but this one will be exceptional.

It is sometimes called the “Hunter’s Moon.” As for why, let’s just say that back in the old days, you wouldn’t want to be a deer out enjoying the moonlight.

The instant of fullness will occur at 7:26 a.m. Thursday, but only a celestial nitpicker would be able to tell the difference between what rises Tuesday night, at 96.5% fullness, and Wednesday, at 99.6%, and that 100% moment. The moon will be up, big and bold on the horizon, at 5 p.m. Tuesday and 5:51 p.m. Wednesday.

Plus, since the moon and sun ride a seesaw, the moon is climbing ever higher as the sun sinks lower in the skies of the approaching winter.

It will be about 30% brighter than it is when the full moon occurs at apogee — when it’s farthest away — and 20% bright than “typical,” said Karen Masters, astronomy and physics professor at Haverford College.

Granted, while it’s not an encore of the northern lights that electrified the skies — albeit briefly — over parts of the region on Thursday night, “the moon is always nice, though,” she said.

And while no earthbound solar eruptions are expected in the near term, nor aurora opportunities around here, “The sun should remain active for a bit longer,” said Masters, “so, hopefully, another one soon.”