Driftless Dark Skies: Comet Tales

We’ll carry with us many memories of the Summer of 2020, but one of my favorites will be the three weeks in July when Comet NEOWISE had so many of looking up together/apart being awed in a dark time by this visitor from far beyond. It was wonderful to hear from so many skywatchers in the Driftless Area and beyond who spotted the comet and shared pictures and reactions and made memories with family and friends. For many, it was a first time glimpsing a comet. I never imagined a career path of “use social media to let people be amazed by a fuzzy thing in the sky”, but I thoroughly enjoyed my brief time as a cometary evangelist. Facebook reports that I was able to reach 400,000 people. In other times there would have been public programs and comet parties. This year, we did it virtually.

Comets are traditionally named for their discoverer, so this one is named for the Near Earth Object Wide-field Infrared Survey Explorer–a space telescope that is watching for things that might cross our path. Like that comet or asteroid that wiped out the dinosaurs 66 million years ago. But comets are the bringers of life as well as death. Much of Earth’s water comes from comets. It’s only 3 miles wide, but NEOWISE has enough water to fill 13 million Olympic swimming pools! Grateful to Dr. Emily Kramer of NASA/JPL for doing the math on the back of her envelope. And comets are also the bringers of meteors. With each flyby of the Sun, comets might lose 1/1000 of their ice and dust.When Earth flies through that trail, pieces of comet dust streak across our skies and we see meteors such as the Perseids in August. So this comet could be around tens of millions of years old. But just a short time in a cosmos almost 14 billion years old.

NEOWISE first spotted its comet on March 27. Many comets break up when they swing by the Sun, but this one survived its flyby on July 3. The Sun heated up this “dirty snowball”, evaporating its ice and creating a coma (cloud) around its nucleus and a tail millions of miles. That’s what had me awestruck when I headed out before dawn on July 7 with my binoculars and spotted it low in the northeast. Best comet I have seen in twenty years. And it got even better as it rose higher in the sky, grew even brighter, and then became visible in the evening sky. One of my favorite science writers, Andy Chaikin, called it “a slender, gently curved feather of soft light suspended among the stars”. I loved that it was so easy to spot as it moved through the Great Bear and the “three leaps of the gazelle”–those paired stars that make up the paws of Ursa Major. One story is that a gazelle was startled by Leo the Lion at a pond and left those three hoofprints as it leaped away to safety. NEOWISE journeyed by them at 40 miles/second.

The Comet was also an invitation to ponder deeper time. This comet was formed over four billion years ago in the early days of our solar system and has spent most of its time in the far frigid dark reaches of the Oort Cloud. Something disturbed its orbit, and it began falling towards the Sun. In this warmer neighborhood, it developed that distinctive tail. When Comet NEOWISE last passed by Earth 4400 years ago, humans were just starting construction of Stonehenge. Its recent flyby of our Sun has lengthened its orbit to almost 7000 years. In the next 35 centuries, NEOWISE will journey far out into our solar system 700 times the distance of Earth to the Sun (and 15-20 times the distance of Pluto) before falling back in for another fleeting flyby of the Sun (and Earth) sometime around the year 8888. Hope our descendants are as awed as we were. Hope they remember us as good ancestors.

John Heasley is an astronomy educator and stargazer who enjoys connecting people with the cosmos. He volunteers with NASA/JPL as a Solar System Ambassador and the International Astronomical Union as a Dark Sky Ambassador. For more information about stargazing in southwest WI, like Driftless Stargazing LLC on Facebook and find out whenever there’s something awesome happening in the skies. Driftless Dark Skies appears monthly in the Voice of the River Valley.

Bon Voyage Comet NEOWISE. So moved by this image by Rob Steffen from the Lone Rock Bridge of the WI River flowing downstream as The Comet streams away from Earth.