Sky & Telescope - September 2021 - 57

Pro-Am Conjunction
by Diana Hannikainen
Chase a
Centaur
With the right equipment, you
can help unravel the nature
of an intriguing class of solar
system objects.
W
ho doesn't love a comet? Many
of you likely enjoyed spectacular
Comet NEOWISE last summer (S&T:
Nov. 2020, p. 14). Such otherworldly
visitors episodically swing by the Sun,
only to be slingshotted back into icy
outer space. How exactly do they find
their way to us from the solar system's
outer reaches?
The answer may lie with this tongue
twister: Comet 29P/SchwassmannWachmann
1.
Gateway objects. Astronomers have
identified a region just beyond Jupiter
that channels most of the faraway
Kuiper Belt objects into the inner solar
system, where they then scurry busily
about flouncing fancy tails. Objects
entering this " comet gateway " region are
called Centaurs, and the most soughtafter
of these is 29P. At about 900 million
km (560 million mi) from the Sun,
29P is one of the most distant objects
to show heightened comet activity.
Normally around magnitude 16-17, the
iceball always exhibits a dust coma, and
it undergoes dramatic outbursts seven
or more times a year. And by dramatic,
we're talking brightening by 3 to 5 magnitudes,
bringing the object within easy
reach of 8- to 10-inch telescopes. During
its brightest outbursts, it might even flare
to magnitude 9 - grab your 6-inch!
Campaign for a Centaur. Several
years ago, then-graduate student Kacper
Wierzchos (now University of Arizona)
was monitoring 29P with a millimeterwave
telescope in Arizona to measure
amounts of carbon monoxide, the most
abundant gas in 29P's outbursts. Comet
29P also frequently exhibits a dusty,
pCOMET IN OUTBURST In this composite photo, Comet 29P brightens during an outburst in
2013, starting on June 16th (lower left) and finishing on July 28th. The comet may very well represent
a linchpin of our continued understanding of solar system formation and evolution.
jetlike feature, and comparing the gas
and dust emissions helps astronomers
unveil the nucleus's composition. Since
visual magnitudes mostly track dust,
Wierzchos scoured the literature for
magnitude estimates from observations
coincident with his own. And then the
light bulb lit up for his advisor, Maria
Womack (University of Central Florida
and the National Science Foundation).
Womack and her colleague Gal Sarid
(SETI Institute) devised a campaign
dedicated to understanding 29P, with the
aim of kicking observations into high
gear. " It's time to go beyond just documenting
the overall brightness of the
object as it changes over time, " Womack
says. " This Centaur is already a muchloved
target of the amateur community,
but the campaign provides the framework
for a more coordinated effort. "
And they're looking for you - observers
with CCD cameras and maybe even
spectroscopes. The bigger your telescope,
the better, but a 6- to 8-inch when the
source is in a major outburst should do
the trick. Brownie points for those who
can record a time series: If you can take
images every 30 seconds, " that would
be amazing, " she adds. " Capturing an
outburst evolution over time would be
really helpful. "
If this tickles your fancy, then go to
https://is.gd/observing29p, where you
can list your recent past and upcoming
observations. (Signing up doesn't commit
you, should you change your mind.)
Professional astronomers with observing
programs at wavelengths other than
visual, such as radio or infrared, can
then consult the webpage, see who else
is out there pointing their scopes at 29P,
and invite them to collaborate.
And yes, the campaign is calling on
professionals to sign up as well! If you're
scheduled to observe 29P, go ahead and
list yourself - let's make this a true proam
endeavor.
All together. The larger goal of
this global project is to provide a place
for observers to meet up and find one
another. New collaborations might
develop independent of Womack or her
colleagues - and that's fine by them.
This campaign is still in its infancy, and
Womack is eager to see how it develops.
The next outburst observing window
runs from September 2021 through
March 2022, but the campaign is
projected to last at least a decade (see
the website). So get out there, take your
equipment with you, and let's help crack
the nut that is Comet 29P/Schwassmann-Wachmann
1. Ultimately, your
data might contribute to our understanding
of the nascent solar system.
¢ Observing Editor DIANA HANNIKAINEN
loves picturing iceballs zipping around
the solar system.
sk yand tele scope .o r g * SEPTEMBER 2021 57
DAMIAN PEACH

https://www.is.gd/campaign29p https://skyandtelescope.org/

Sky & Telescope - September 2021

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