Sky & Telescope - January 2022 - 53

2009 IMPACT: NASA / IRTF / JPL-CALTECH / UNIVERSITY OF OXFORD
Impact plume
pBrazilian amateur José Luis Pereira captured
the most recent impact event at 22:39 UT on
September 13, 2021, using his 10.8-inch Newtonian
reflector and a QHY5III462C video camera
(see page 10).
Impact area
cist Ricardo Hueso, and Jon Juaristi
Campillo of the Center for Astronomy
at Heidelberg University in Germany
wrote software that searches for impact
flashes in video recordings. Employing
a fast and efficient algorithm based
on differential photometry, DeTeCt
(https://is.gd/DeTeCt) is an opensource
application that planet imagers
can use on their own computers to
identify impacting events. The program
eliminates the need to perform a very
tedious and time-consuming frame-byframe
hunt for bright spots of fleeting
duration by searching for localized
brightness anomalies and automatically
generating a detection image and report.
Using DeTeCt is one of the core
activities of the Europlanet Planetary
Space Weather Services. The project's
website (https://is.gd/europlanet) provides
a tutorial for using the program, a
download link, and an up-to-date list of
results. The group has also analyzed
data acquired during almost two
decades of Jupiter observations containing
more than five months of continuous
video recordings. Scrutinizing this
long span of data allows more accurate
estimates of the frequency of impacts,
though considerable uncertainties
remain because it's difficult to make a
statistical analysis of events that have
been observed only a few times.
Analysis of the light curves of the
five flashes recorded between 2010 and
2017 indicates they were produced
by impactors measuring less than 20
meters in diameter (assuming a modest
density typical of cometary material).
The energy released by these events is
comparable to the February 13, 2013
" superbolide " airburst over the Russian
city of Chelyabinsk, which was 30 times
more powerful than the atomic bomb
dropped on Hiroshima.
A recent estimate by Spanish astronomer
Agustin Sánchez-Lavega of the
impact rate of objects in this size span
striking Jupiter ranges from 10 to 65
per year. He notes that only a fraction
of these can be observed from Earth for
several reasons:
Impact sites are evenly distributed
over Jupiter's visible day and averted
night hemispheres.
There's only an eight-month observing
window each year when Jupiter is
readily visible.
Most observations tend to cluster
around the date of opposition.
The visibility of impacts at high latitudes
on Jupiter's oblate globe is poor.
Impactors larger than about 300
meters, like the one that produced Wesley's
2009 scar, yield dark debris fields
 The debris field of an impacting object in
2009 appears bright when seen through a
890-nanometer methane filter.
observable with amateur instruments
that persist for weeks. According to Sánchez-Lavega,
these events probably occur
once every 3 to 16 years and should be
observed about once every 7 years.
Jupiter has long been known as " the
amateur's planet " due to its rich legacy
of discoveries by backyard astronomers
(S&T: Nov. 2021, p. 52). Professional
astronomers find it easier to collaborate
with this worldwide amateur network
than to persuade the committees
that allocate telescope time to allow
a round-the-clock, long-term vigil for
sporadic events.
A growing band of dedicated amateurs
continues to provide monitoring of
Jupiter during each apparition. Thanks
to DeTeCt software, imagers can analyze
video recordings of the planet long after
the end of the annual Jupiter observing
season. So make time to scan your
unprocessed planetary videos - you
may have an unnoticed impact event in
your possession awaiting discovery. The
opportunity to collect valuable data and
make real contributions to planetary science
has never been greater.
¢Contributing Editor TOM DOBBINS
has yet to witness an object hit Jupiter
himself, but he enjoys vicarious views
provided through the internet.
sk yand tele scope .o r g * JANUARY 2022 53
https://www.is.gd/DeTeCt https://www.is.gd/europlanet https://skyandtelescope.org/

Sky & Telescope - January 2022

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

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