We have a once-in-6,800-years opportunity to see a comet in Washington’s skies
A telescope in space meant to detect dangerous objects headed toward Earth found a passing comet in March. Now, you can see it in the night sky above western Washington.
Comet NEOWISE is in the evening sky, just below the Big Dipper through July and possibly into August, astronomers say. It’s marked by two graceful trails.
While the world was engrossed in the exploding coronavirus pandemic March 27, NASA’s Near-Earth Object Wide-field Infrared Survey Explorer spotted the comet.
“It’s helping us find stuff out there,” said Bill Vinson, an amateur astronomer and member of the Tacoma Astronomical Society, said of the space telescope. “We don’t want to go the way of the dinosaurs.”
NEOWISE is still getting closer to Earth, making its closet approach on July 22. Don’t panic — there’s no chance of a collision. However, the comet’s luminosity is decreasing because it’s getting further from the sun every day.
For local astronomers, the comet is proof that even in our solar system, space still holds surprises.
“It’s abuzz among people like us who are amateurs,” Vinson said.
Comets orbit the sun, just like Earth and the other planets. But NEOWISE has a highly elliptical orbit that sends it far past Pluto, Neptune and Uranus, said Bernard Bates, an astronomy instructor at the University of Puget Sound.
At NEOWISE’s furthest point from Earth, the sun would look only like a bright star, Bates said. The comet would remain small and dark, imperceptible to Earth’s residents and their instruments.
“Still, it’s under the sun’s gravitational pull,” Bates said.
NEOWISE’s orbit takes it past earth once every 6,800 years. There are no historical records of its previous visits. Comets and their predictable visits have figured prominently in history and astronomy. One of the most famous comets, Halley, makes a trip past Earth every 75 years. It’s next visit will be in 2061.
What is a comet?
“Comets are things that were formed when the solar system was forming,” Bates said. “They’ve been in cold storage very, very far from the sun.”
When a comet gets close enough to the sun, it becomes visible and begins to melt, giving off the signature tails.
Typically, Bates said, a comet is made of frozen water, methane, ammonia and other substances. Because space is a vacuum, the ice melts directly into gas.
Without their tails, comets could be just passing blobs in the night sky. But, like a peacock, a comet is all about its tail.
NEOWISE has two tails. As the ice vaporizes and moves away from the comet’s surface, it drags dust with it. The expanding atmosphere of gas and dust is then pushed away by the solar wind.
“If you didn’t know anything about it, you would think that the tail is like a trail left behind, like a car speeding down a dusty road,” Bates said. In fact, he said, the direction of the tail has no relationship to the direction the comet is going.
At night, the tails you’ll see point away from the sun below the horizon. One tail has a slight curve.
Those dust particles get left behind in the comet’s orbit. If Earth passes through them, they’ll produce a meteor shower. The annual Perseid meteor shower in August is an example, Bates said. They are the leftovers from comet Swift–Tuttle, which approaches the Earth/moon orbit every 133 years (next visit: 2126).
NEOWISE gives earthlings an opportunity to view a comet that has been in space since the formation of the solar system, some 4.5 billion years ago.
“This is why comets are interesting to study, because they’re like a frozen snapshot of what conditions were like when the solar system was forming,” Bates said.
Comet over Tacoma
Amateur astronomer Vinson has spent the past several nights and early mornings viewing and photographing Comet NEOWISE for his YouTube channel.
Last week, when the comet was visible in the early morning hours, Vinson had several cameras set up along Ruston Way. He switched to evening hours when the comet became visible after sunset this week.
“A lot of people are coming around,” Vinson said of the mostly mask-wearing crowd. “I was basically giving a one-man show with the comet as I was taking the pictures and doing the time lapse movies.”
Vinson said Comet NEOWISE is about half as impressive as Comet Hale-Bopp, a spectacular comet that visited Earth’s night skies in 1996-1997.
Vinson had no problem spotting the comet within city limits, but he is planning a night time trip to Mount Rainier to get more photos and video.
“Go up to Mount Rainier and get away from city lights, and it’ll be easy to find,” he said.
Now is the only opportunity to see NEOWISE for the next 6,800 years.
The 3-mile-wide NEOWISE is just one of the 3,650 known comets, according to NASA. There are likely billions of others orbiting the sun, NASA says.
“An incredibly bright comet could show up at any time,” Bates said.
For amateurs like Vinson, NEOWISE is reward for their diligent scanning of the night skies.
“Always be on the lookout, because you never know what you’re going to find or what you’re going to see up there,” Vinson said.
Finding Comet NEOWISE
The comet will become visible in the evening sky, after sunset. Look to the northwest, between where the sun set and true north. Find the Big Dipper (Ursa Major) and then look below it.
Hold your fist at arm’s length and count three to five fists above the horizon.
The best viewing spots are going to be away from city lights and obstructions.
Binoculars, telescopes and telephoto lenses will help you see the comet’s tail.
Astronomers can’t predict how long the comet will be visible. It makes its closest approach to Earth on July 22.
