A Little Cometary Perspective

In these Covid-deprived times our ability to embark on ambitious peregrinations is greatly stifled. We are encouraged to stay close to home, abjure crowded airplanes, keep our distance, and thereby hope to avoid emulating the unhappy fate of the six hundred thousand of our fellow humans who have already succumbed to the virus. At this time of year I would ordinarily be enveloped in the quiet, restorative delights of the woods of Big Bras d'Or, the wildflower-festooned trail to Dalem Lake, the vocal stylings of the Swainson's thrushes, black-throated green warblers and white-throated sparrows of Boularderie Island. Perhaps the pandemic will have abated enough to permit a return to Cape Breton in 2021. Perhaps not.

I am obliged to content myself with horizons reachable on foot from my James Bay door, by bicycle, or by a short drive in gasoline-powered conveyance. But these days—perhaps I should say nights—another sort of peregrination provides happy, contemplative distraction. I admit to being one among  my kind fascinated by comets. Yes, comets. I get excited whenever a new comet is discovered and I have the prospect of seeing it with my own septuagenarian eyes. In late March, on its journey to our corner of the solar system, a new comet was detected by a space telescope, the Wide-field Infrared Survey Explorer absorbed in its Near-Earth Objects mission—NEOWISE for short. Comet Neowise has an alternate, even more prosaic moniker, C/2020 F3. I find neither name as evocative as the names Halley, Hale-Bopp or Hyakutake but that is a mere quibble. Any visible comet is a joy to behold, an inducement to contemplate our significance in the greater scheme of things.

Often dubbed "dirty snowballs", comets are typically made of dust, gas and the ionized gas the scientists call plasma. When invisibly minding their own business in the outer reaches of the solar system comets are very cold, something in the order of minus-220 Celsius, but as they approach the innermost zones of the solar system the surface temperature can shoot to an opposite extreme: heat measured in the millions of degrees. And that is when we humans get to see them: it is the heat of the sun and the solar wind that produce the comet's corona and the tail that extends as much as ten million kilometres.

A few nights ago Jan and I made our way in evening twilight to Highrock Park in Esquimalt to see the new comet. We were not alone: twenty or thirty others were also gathered at Highrock for the show. Neowise is a wee thing, a mere five kilometres in diameter, but even at a distance of a hundred million kilometres the corona and tail make it is easy enough to spot, especially if the observer is armed with a decent binocular. It was of course Jan, aka 'Hawkeye', who spotted it first. I managed to get a decent image of Neowise with my long-lens Sony.

One viewing was not enough. Last night we went out again. By 11 pm the summit of Victoria's Mount Tolmie was crowded with people and their vehicles, all gathered for the same purpose. Neowise once traveled at a sedate 3,200 kilometres/hour but the slingshot effect of the sun's gravity has increased the iceball's pace to 28,000 kph. That works out to about 7.78 kilometres a second, quite a bit faster than Usain Bolt in his prime. The comet will make its closest approach to Planet Earth July 22 by which time it will be a mere 103 million kilometres distant. You still have plenty of time to see it: take a bino to some location—the darker the better—with an open view to the northwest. I promise it will be easy enough to see.

Where is Neowise headed? Well, back to the Oort Cloud is the short answer: the far reaches of the solar system. Solar system distances are measured by the Astronomical Unit, the distance from the sun to our little planet, 152 million kilometres. At aphelion, the comet's greatest distance from the sun, Neowise will be in the order of 630 AU away from us. The comet will need a few thousand years to reach aphelion and commence its next circuit to the sun. For a sense of what 630 AU means consider this: Voyager 1, launched 43 years ago in 1977 and speeding along at 17 kilometres/second is now about 150 AU from its launch pad. When will we see this comet again? The experts tell us it will be 6,800 years before Neowise delivers a return engagement.

Neowise delivers a tonic over and above its fascinating bare facts: when a fellow is inclined to fret about the state of human affairs and the danger that Donald Trump might be reelected leader of the free world, the comet offers a little perspective.