One regret that I (and likely many other observers have) is losing observations that we recorded, sometimes of once-in-a-lifetime events. In preparing for an eventual downsizing, I started to tackle going through the accumulation of papers and files in the basement. I collected and scanned my loose-leaf logbooks and have lots of wonderful observations from them. I was disappointed, however, that I did not come across any from the summer of 1994 when Comet Shoemaker-Levy 9 crashed into Jupiter in spectacular fashion. And then this week – voila! I uncovered about a dozen observations of Jupiter from that year. And yes, among them a few of Jupiter post-impact.
Looking at them brought pleasant flashbacks. One of the most
dramatic sights I have ever had the good fortune to witness as an amateur
astronomer was those amazing bruises on the giant planet so readily seen in my
modest telescope.
For those who were not yet observing (or not yet born) in
July 1994, a brief reminder: Comet Shoemaker-Levy 9 had been torn apart by
Jupiter’s gravity on an earlier close pass and was on a collision course.
Between 16 and 22 July a string of fragments slammed into the giant planet’s
southern hemisphere at roughly 60 km/s. As the impacts rained down on Jupiter just
beyond the limb as seen from Earth, we anxiously held our breath as to whether
we would be able to see any evidence of the hits. To everyone’s surprise and
delight, a short time later dark, high-contrast debris fields rotated into view
and remained prominent for months.
Amateurs around the world suddenly found themselves observing
features that rivaled or exceeded the Great Red Spot in visibility. My own
records begin a few days after the bombardment.
20 July 1994, 1:10 UT
Telescope: 6-inch f/8 Criterion RV-6 Newtonian at 124×
Seeing 5/10, transparency 1/6 under murky, humid hazy
My drawing shows two large, dark oval spots sitting near the
south temperate region. My notes still convey the astonishment:
“Through murky, humid haze came the view of a lifetime – I could
scarcely believe how dramatic and contrasty these two impact sites are! Oval
& featureless like 2 sunken eyes, (they are the) first objects you notice
when looking at the planet. Other major belts are visible, no features noted
but serious study impossible due to large number of public at our observing
site wanting a view. Following spot transited ~ 10 pm EDT.”
For context of that report we were set up at an outreach
site (while not noted in my report I am pretty sure it was out at the Irvine
Nature Center on the grounds of St. Timothy’s School in Stevenson), and the
impact scars were so obvious that people lined up for a look even under
mediocre transparency. The “sunken eyes” description still feels exactly right
– featureless, ink-black ovals that dominated the disk the moment the planet
came into focus.
25 July 1994, 1:30 UT
Same telescope and magnification
Seeing 4/10, transparency 1/6
On this date three distinct scars were visible. The central
one was especially impressive:
“Kind of hazy but
seeing fair; the central spot is incredible, easily size of GRS and noted
readily even at 70×. The spots preceding & following are readily seen with
the following one weakest of the three. Hard to see either a STB or NTB.”
The drawing shows the three dark spots strung across the
southern latitudes, still high-contrast enough to punch through a mid-summer
haze.
8 August 1994, 1:20 UT
Again the RV-6 at 124×
Seeing 4/10, transparency 3/6
Nearly three weeks after the final impacts the scars were
still unmistakable:
“Three large spots noted, the central one having a darker
core I believe and showing signs of being stretched out E-W. Spots are still
incredibly contrasty & easy to see. STB noted with a gap in it but no oval
present west of the CM. SEB split, NEB darkest belt with a notch on south side
west of the CM. NTB very vague, NPR evident.”
The central scar had begun to elongate east-west, yet the
overall visibility remained remarkable for features that were, after all,
simply debris suspended high in Jupiter’s atmosphere.
Looking at these notes and sketches more than three decades
later, several things stand out. First is the sheer drama and significance of
the event itself – nature delivering a never-before-seen planetary-scale
collision that even modest apertures were capable of revealing. Another aspect
is reflected by the fact that a simple 6-inch Newtonian battling summer haze
was more than adequate – and that rewrote how we looked at the threat from
comets or asteroids impacting a planet. While I do not have access to ALPO
reports from that summer, I suspect even a quality 80mm refractor would have
been up to the task.
Will anyone look at my recording of the Shoemaker-Levy 9
crash as seen through my little scope in a couple decades from now? Not likely. It will fade into the
backwaters of the internet or be completely lost again fifty years from now.
But for the moment there is joy and satisfaction in holding in my hands once again
my documentation of one of the most momentous astronomical events visible to
amateur astronomers in the 20th century.
