A newly discovered comet is streaking through the night sky. The comet NEOWISE, a 4.5 billion-year old icy rock essentially unchanged since the formation of the solar system, is now visible to the naked eye throughout New England. It won't be visible for long, and glimpsing it is a "once in a hundred lifetimes” opportunity.
"The tail is so delicate and so pretty," said Kelly Beatty, senior editor for Sky and Telescope Magazine in Cambridge. "It's just kind of a picture-perfect comet."
The comet has been visible in recent days predawn but can now also be seen in the evening hours, starting about an hour after sunset. Beatty said if you want to see it, look to the Northwest — that’s to the right of where the sun sets — and try and spot a more familiar object the sky: the Big Dipper.
"We use this very exacting way of measuring distances in the sky. You stretch out your arm and clench your fist," he said, wryly. "And that’s about 10 degrees of sky. The comet’s about three fists below the Big Dipper.
You’re looking for a hazy light and that classic comet tail. Beatty says a dark location is best if you can find one. For those closer to cities where there’s often light pollution, one inexpensive item might help.
"If [you've] got a pair of binoculars and you kind of fish around in there, you will see it," he said.
It was first seen by scientists only in March of this year. Comets are traditionally named for their discoverer, and so it was in this case, as it was first observed by a NASA instrument called the Near Earth Object Wide Field Infrared Survey Explorer.
In what I think we can all agree was a good move, they went with the acronym, NEOWISE.
Comets are small, solid objects, said Boston University astronomy professor Jeffrey Hughes. They don’t make their own light, and without a little help from the sun, they would pass by the earth with little fanfare, largely invisible.
"This one is maybe 3 miles across," he said of NEOWISE. "You’d never see that. It’s just too small."
But what makes them special is the presence of water ice around their solid core and an orbit that takes them around the sun — close enough to melt off some of that ice and make them glow.
"So what you see is the cloud of primarily water vapor that’s evaporated from it reflecting sunlight," he said.
They are also pretty common. In fact, Hughes said about a dozen new ones are discovered every year by scientists, mainly specialists in the field. And most are too faint to be seen without expensive observational equipment.
"What makes this one different is it’s passed very close to the sun," said Hughes. "Which meant it got pretty hot, evaporated a lot, [and] got a big cloud to reflect sunlight so it’s very bright."
Another thing that makes it unique is its orbit which, despite the fact that NEOWISE was just discovered few months back, has already been worked out thanks to Newtonian mechanics. All scientists needed were a few images that allowed them to calculate a comet’s speed and distance from the sun.
"I'll have my Sophomores compute that in their planetary class [that] I will teach next semester," he said.
NOEWISE’s orbit is cigar-shaped and extremely long. It will spend the next 3,000 years or so traveling away from the sun, about 100 times further than Pluto's orbit, before looping back and making another pass through our neck of the woods in about 6,800 years.
For scientists, comets provide an up-close glimpse back in time. And studying them gives them all sorts of clues about how the earth formed and developed. But it’s been since Hale-Bopp in 1997 that a passing comet has been this bright. And Hughes says that gives all of us a rare chance to observe for ourselves and ponder the kind of questions that drive him to do what he does every day.
"Where did we come from? Where are we in this universe? You can argue that that’s perhaps one of the most important questions we can, as mankind, ask," he said.
And, if that’s a little heavy for you, Kelly Beatty — who dragged himself out of bed at 3 a.m. last week to catch a glimpse of NEOWISE in the predawn hours — offered this endorsement.
"Boy just looking at the night sky is awe inspiring," he said. "This is a transient visitor from the great beyond. I encourage everyone just try and get a look at it. There are a lot of things that happen in the sky. This is one of the pretty ones."
You’ve got this week for sure, and maybe an another week after that to have your own look at NEOWISE. After that you’ll have to wait until the 89th century.