DOTTED YETI / SHUTTERSTOCK.COMFOCAL POINT by Joe Ulowetz
hinting that the large gravitational fi eld
of something is “herding” them.
Sedna’s current brightness is mag-
nitude 20.9, or about two magnitudes
fainter than I’ve done before. Stacking
my images might just let me go deep
enough, I thought. So I spent two suc-
cessive nights photographing Sedna’s
location. Then I stacked together the
images taken each night and blinked
the results, looking for any changes.
Nothing. I couldn’t even convince
myself that there might be a barely
visible smudge. Unfortunately, I just
couldn’t go deep enough with my loca-
tion and equipment. So I looked over
the rest of the image, to see if maybe I
had at least captured some other aster-
oid or maybe a variable star.
And that’s when I noticed it.
Off near the edge of each image —
but in slightly different locations — was
a tiny dot that I estimated to be about
magnitude 18. It hardly moved between
the images, less than what I expected
Sedna would do. That implied it was far-
ther out than Sedna, but at magnitude
18 it must be large to be visible that far
away — much larger than Sedna.
I knew of astronomers’ predictions
about Planet 9, but if it was as brightBut for one dizzying day
I couldn’t rule out the
possibility that I had.I JUST WANT TO MAKE THAT CLEAR
from the start: I didn’t discover
Planet 9, that hypothetical, super-
Earth-size world posited to lie in the
outer realms of our solar system. In
fact, I didn’t discover anything. But
for one day I couldn’t help but wonder:
Could it be?
I live in suburban Chicago, where
third-magnitude skies are a good night.
But with just a moderate-size scope
(9.25-inch SCT) and a good CCD cam-
era, I can reach really faint objects that
I could never have hoped for when I was
limited to visual observing.
Pluto, for example, is easy to see at
magnitude 14 with an exposure of a
few seconds. If I increase the exposure
to around 5 minutes, I can capture
between magnitude 18 and 19 in good
weather. I’ve imaged faint targets like
the dwarf planet Eris many times.
But I wanted to push my limits. I
thought it’d be really exciting to fi nd
Sedna. Roughly three times farther out
than Neptune, that sizable planetoid
travels far beyond the main Kuiper Belt
and out toward the Oort Cloud. And
Sedna is one of the six small worlds
whose aligned, elliptical orbits are tilted
about 20° off the ecliptic — collectivelyas magnitude 18 someone would have
found it already. There really wasn’t
any chance that I was seeing it, right?
Besides, they’d predicted it would lie
in a patch of sky west of Orion, while
Sedna was currently located in southern
Taurus, which was...... west of Orion.
My heart stopped. It couldn’t be. It
would have needed all previous surveys
to have missed it. Impossible, right?
Probably, but I just couldn’t walk
away. I changed my imaging plans and
dedicated a third night to re-imaging
the fi eld where Sedna lay.
And when I processed the new
images: nothing. Apparently a pair of
cosmic rays had hit my camera in nearly
the same spot on two successive nights,
making them look together like a slow-
moving object.
So, in the end, I didn’t discover
Planet 9. But for 24 hours, I couldn’t
prove that I hadn’t.
¢A software engineer during the day,
JOE ULOWETZ uses his backyard
observatory every clear night to study
cataclysmic variable stars for the Center
for Backyard Astrophysics (cbastro.org),
plus other objects of interest.84 JUNE 2020 • SKY & TELESCOPE
I Did Not
Discover
Planet 9
E23G671