Sky & Telescope - December 2022 - 4

SPECTRUM by Peter Tyson
Picture Perfect
IT'S AMAZING HOW INVENTIVE astronomers can be when they want
to record a celestial object they can't see. They simply won't be
stopped by distance, overwhelming starlight, or intervening gas and
dust. If there's a workaround, they'll find it.
To show you what I mean, I direct your attention to four images
in this issue. Collectively, they display the prodigious skills that both professionals
and amateurs wield to secure pictures of elusive entities.
First, look at the image of Sirius, the Dog Star, on page 29 of Ken Croswell's
cover story. As the brightest star in the night sky, Sirius is easy enough to
photograph, but notice the tiny dot in the lower left. That's Sirius B, a companion
white dwarf star. Sirius B is smaller than Earth and roughly 10,000 times
fainter than Sirius (aka Sirius A). How did astronomers possibly get a picture of
it next to that blinding spotlight? In short, they used
the Hubble telescope and some technical cleverness.
(As it turns out, even amateurs with modest scopes
can pick out Sirius B - see https://is.gd/SiriusB.)
Now, turn to page 12, where you'll see a silhouAnother
exquisite portrait:
The planetary nebula
HFG 1 (see page 20)
ette of the black hole residing at our galaxy's center.
Why is this image astounding? Because the black hole
is 26,000 light-years away, its shadow on the sky is
roughly the size of a grapefruit seen at the distance of
the Moon, and, most significantly, it's hidden behind
clouds of dust and gas. How did astronomers obtain
its portrait? Camille Carlisle gives you full details in her article, but the key was
using a slew of radio telescopes that can " see " right through interstellar dust.
Next, behold the image on page 60, particularly its inset. Taken by amateur
Rolf Wahl Olsen, this photo captures light echoes from SN 1987A, the closest
supernova to have appeared in modern times. Like sound echoes, light echoes
bounce off distant objects - in this case, cosmic dust clouds - and reach us
later than the direct light from an event like SN 1987A. Again, you'll have to
read Olsen's feature to learn just how he pulled off this stunning feat. But just
think: You're viewing light from a supernova that occurred decades ago.
Finally, consider the sketch on page 57. See all that nebulous stuff on either
side of the Andromeda Galaxy? That's galactic cirrus - dust and gas spewed out
by supernova explosions. Sketching enabled amateur Mel Bartels to depict the
gauzy cirrus in a strikingly effective way.
Of course, many other images in this issue (and all issues) of S&T exhibit
just how creative astronomers can be when they want a
picture. As our field advances, who knows what celestial
scenes we'll enjoy down the road?
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Sky & Telescope - December 2022

Table of Contents for the Digital Edition of Sky & Telescope - December 2022
