Skywatch - 2021 - 5

I'm not exactly what you'd call a "morning person."
The idea of being up and about before the Sun rises
strikes me as a little eccentric and possibly unhealthy.
That's why the first dawn appearance of Sirius doesn't
register with me. Instead, I'm more aware of events
occurring in the evening, or late at night. And because of
that, nothing signals the end of summer quite like spotting Orion's Belt cresting the hills to the east of my home
for the first time in autumn. No matter what the outside
temperature actually is, it suddenly feels colder. Orion's
return is always a mixed blessing. While I'm happy to see
an old friend once again, his arrival also reminds me that
yet another year is quickly drawing to a close.
Once you've gotten to know the stars and constellations, the seasons in the sky will become as familiar
as those here on Earth. Winter is the domain of Orion,
Taurus, and Canis Major. Spring brings us Boötes, Leo,
and Virgo. The Summer Triangle and the respective constellations of its component stars (Vega in Lyra, Deneb
in Cygnus, and Altair in Aquila) signpost the mildest
season, and autumn's chill is heralded by Pegasus, Perseus, and Capricornus. The more nights you spend under
the starry sky, the stronger these seasonal associations
become. Even if you go no further, recognizing these patterns connects you to the universe beyond your day-today existence.
The annual parade of stars and constellations is one
thing, but there are also cycles that repeat over much
longer timespans. Take big, bright Jupiter, for example.
When the planet is at its best this year (around its date
of opposition, on August 19th, when it's visible all night
long), it resides in the constellation Capricornus, near the
border with neighboring Aquarius. Because Jupiter takes
slightly less than 12 years to go around the Sun, it shifts
eastward roughly one constellation of the zodiac (of which
there are 12) each year. Next opposition, Jupiter will be
in Pisces, the one after that, in Aries, and so on. Jupiter's
orbital period also means the planet returns to the same
general spot in the sky every 12 years. Indeed, Jupiter
was last at opposition in Capricornus in 2009, and it will
be in the vicinity again (just over the border in western
Aquarius) in 2033.
Mars has its own, delightfully complex rhythms. The
Red Planet brightens dramatically when Earth catches
up to it in its orbit, approximately every two years. But
Mars puts on its finest telescopic display only during the
very closest encounters (called perihelic oppositions). We
had one such opposition last October, and Mars won't be

that close again until 2035 and 2037. I feel the chill hand
of mortality when I consider I may have only a couple
more chances to see Mars as well as I did in 2020. Ulp!
Of course, there are also sky events that are literally "once in a lifetime." Halley's Comet is the most
famous example. It swings by the Sun, when it brightens to visibility, every 76 years - slightly less than the
lifespan of the average American. Mr. Halley's famous
comet last graced our night sky in 1985/86, so that's it
for me (and my friends) - one and done, as they say.
Some lucky individuals might see Halley's Comet
twice in a lifetime, but that's pretty rare.
Comets also remind us that life is occasionally
punctuated with moments of surprise. The unexpected
appearance of a really bright comet is something to
cherish because no one knows when, or indeed, if,
another will come along again any time soon. Last
summer we got to enjoy the gift of Comet NEOWISE
(C/2020 F3). It was the first conspicuous comet in several decades and a visual delight.
Compared with the transient delights of comets,
there's a kind of comfort to be found in the unchanging
nature of the constellations. Although their seasonal
comings and goings mark the passage of time, the
constellations also possess a reassuring constancy.
When I was a child, I was fascinated to watch three
stars rising in a distant, V-shaped valley. I wondered,
how could these stars be so perfectly aligned and identically bright? A trip to the library later, I was able to
identify them as the stars of Orion's Belt. You could say
that early encounter was life-changing - it set me on
the path I still tread today.
Late last night I stepped into the backyard for a
breath of fresh air. It was a mild, late-summer night
with a gentle breeze slipping through the leaves and
branches of nearby trees. I could hear a pair of owls
conversing in the distance - their pensive calls rising above the persistent raspy din of chirping crickets. Above an apple tree to the east, Orion rose. We
exchanged a brief greeting and went our separate
ways. I returned to bed happy to know that the starry
hunter (and his trusty dog, Canis Major) will be my
companions the rest of my life.
Sky & Telescope Consulting Editor GARY SERONIK began
exploring the night sky as a child in rural British Columbia,
Canada. Orion was the first constellation he identified and,
decades later, remains a favorite.

SK Y WATCH 2021

Skywatch - 2021

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