The annual Perseid meteor shower will put on its best and brightest display between Aug. 12 and 13 from 11 p.m. to 4:30 a.m. The atmospheric conditions are near perfect. The weather conditions are not.
A total solar eclipse is darkening skies Wednesday — at least, over Europe. The eclipse isn’t visible in the U.S., but astrophysicist and University of Iowa Assistant Professor Dustin Swarm said it will still benefit the Perseid show.
“The consequence is that we are in a new moon phase, which means the moon won't be up, shining brightly, obscuring meteors,” Swarm said. “So we'll be able to see even fainter meteors than we typically would.”
But weather could dampen Iowans viewing plans. Forecasts show rainclouds covering most of the state Wednesday night. That’s bad news for visibility. But Swarm remains optimistic.
“My weather app shows a partially cloudy icon, so I'm hoping that I'll be able to sneak some peeks when I'm out on my evening walk,” he said.
What you could see
If stargazers in Iowa could see through the clouds, they would likely spot one or two meters per minute. That’s already a pretty spectacular show, Swarm said, but Wednesday is also the night to see the most “fireball meteors.”
"[Those are] larger chunks of debris that burn up more spectacularly as they enter the atmosphere and leave a larger, brighter trail,” he said.
Swarm said the largest burning chunks are probably about 15 pounds, with the circumference of a bowling ball. He estimates the smallest ones that would still leave a visible trail might be pebble-sized.
All of the chunks are debris left behind by the Swift-Tuttle comet. They radiate every year from a region near the Perseus constellation, a vaguely man-shaped cluster of stars in the northern sky. But Swarm said it may be easier for a beginner stargazer to orient themselves with a different constellation.
“I find an easier constellation that's actually close by is Cassiopeia,” he said. “Cassiopeia looks like a big 'W' in the sky, and the stars are fairly bright. If [people] look for Cassiopeia, then they would look below the leftmost edge of the 'W,' and that's about where the radiant would be located.”
Wednesday isn’t the only night to catch the Perseids. Attentive observers have been able to see meteors since mid-July, and showers will continue until around Aug. 24. So if thunderstorms roll through the area overnight, hold out hope for a clearer night over the next couple weeks. If all else fails, there’s always next year.
A brief history of the Perseids
Astronomers didn’t always know the Perseids happen every year.
Swarm said the earliest reference to the shower is from Chinese astronomers in 36 C.E. But he said it wasn’t until the 1830s that scientists realized it was an annual event, and it wasn’t connected to the Swift-Tuttle comet until the 1860s.
Meteor showers like the Perseids can help astronomers learn what makes up a comet, Swarm said, which can have surprisingly far-reaching implications.
“We think the comets come from a region beyond where Pluto would be, called the Oort Cloud. So this would be leftover debris from when the solar system is forming,” he said. “Seeing what that debris at the outer edges of the solar system consists of would give us more clues about the protoplanetary disk from which our planets formed.”
In other words, each pretty color crisscrossing the sky could hold secrets about the beginnings and ends of the solar system. But the shiny, sparkly display doesn’t have to be that deep.
“We can't discount the appeal of having such a dynamic astronomical show, even for professional astronomers,” Swarm said. “We enjoy watching that as well.”
