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.
