Is my three-and-a-half-inch telescope large enough to see
the spots on Jupiter? That question is foremost in my mind as I sit down at
noon to watch today's NASA briefing. My father is watching, too.
Don Savage opens the program as usual and introduces the
panelists. Dr. Steve Maran is back as moderator, and Dr. Lucy McFadden has also
returned to deliver news updates. Shoemaker-Levy 9 co-discoverer David Levy is
back after an absence of several days. Newly arrived are Dr. Roger Yelle of the
University of Arizona, who is part of the Hubble Space Telescope's Spectroscopy Team, and Dr. Renee Prange from the
French Institute Astrophysique Spatiale in Orsay, France, who is a member
of the Hubble Space Telescope's Upper Atmosphere Imaging Team.
Steve states that Fragment P2 should have hit Jupiter within
the past hour, and that the triple-shot sequence of the Fragment Q, R, and S impacts
occurring ten hours apart will begin today at 3:32 p.m.
Dr. Roger Yelle has a new discovery to report. A new graph of
spectroscopic data from the Fragment G impact is displayed, taken by the Hubble
Space Telescope's Faint Object Spectrograph in the 150 to 3000 nanometer
wavelength range (ultraviolet light). It follows the same format as yesterday's
spectroscopic results, in the form of a curve that dips to show how much less
light at certain wavelengths is present after the comet impact, compared with
before. The deepest dip is the ammonia dip we saw yesterday, at around 200
nanometers. However, this graph includes a wider range of wavelengths, and there
is a plateau to the right of the ammonia dip. The right part of that plateau
consists of a number of closely-spaced wiggly lines -- "it looks sort of
like a fishbone," says Roger -- in the vicinity of 270 nanometers. That
indicates absorption by some other type of molecule. It "was very exciting
when we saw that yesterday," relates Roger, "but we had no idea what
it was."
Roger gives a very thorough introduction to this new
discovery. "Molecules will absorb at specific wavelengths -- specific
colors -- that are their own signature," he states, "so one molecule
will absorb at one wavelength; another molecule will absorb at another
wavelength." The shape of this new signature offers some clues as to the
nature of the molecule that's causing it. "It's a very regular spacing of
ripples, and that tells you that it's a simple molecule," explains Roger. "Secondly,
the ripples are close together, and that tells you that it's a heavy
molecule."
He describes the curve and the challenges the researchers faced
in determining which substance those wiggles represented. It wasn't something
that they were expecting, so they "had to go off and search spectra of all
the molecules [they] could think of to find out what [it] was -- and none of
the simple ones matched up!" It wasn't until "about 3:00 in the
morning" that they began to put the pieces together on the nature of that
molecule ...
Dad sits calmly through this entire discourse, unaware of
how tantalizingly few solid findings have come out of these early comet impact
observations. But I am in an extreme state of suspense. Is it water? If not
water, then what is it? Is it part of the comet? Part of Jupiter's
atmosphere? It must be something pretty exciting or unusual if they didn't
think to look for it right away. This is one of the richest finds we've had
yet: a tangible clue to the chemistry that has been going on. But Roger is
taking his time in telling us, drawing out the story.
Finally, after keeping us in suspense for five
excruciatingly long (to me) minutes, he divulges the substance's name.
"Those features are a very good match to the spectrum of sulfur ... sulfur gas," Roger states.
More specifically, it's a diatomic sulfur molecule -- a pair of sulfur atoms bonded together.
Is this sulfur gas from the comet or from Jupiter? It could
be either one. "Sulfur is seen in most comets, I believe," offers
Roger, but he says that Jupiter's atmosphere also contains sulfur.
Roger notes that there appears to be yet a third type of molecule
in the vicinity of the ammonia one, and that while it could yet turn out to be
something else, "the spectrum is consistent with the presence of hydrogen
sulfide."
There is still no sign of water at the impact sites. By now,
this absence of detectable water piques my curiosity almost as much as it does
that of the scientists who have been continually searching for it.
After Dr. Roger Yelle, it is Dr. Renee Prange's turn to
speak. "Jupiter, like the Earth, is a strong magnet," Renee begins. Like
the Earth, it experiences auroras at its poles.
We now see black-and-white
images of the auroras of Jupiter, taken by the Hubble's Wide Field and
Planetary Camera 2 in the far ultraviolet. The first image was taken before the
comet impacts, and it shows the auroras at Jupiter's North and South poles. I
think it's the same one we saw Monday morning, that "best-ever" image
of Jupiter's auroras.
The second image looks a lot like the "after" image of the auroras that we saw on
Monday, with one startling exception: two bright areas have appeared below and
to the left of the polar aurora at Jupiter's North Pole!
This presents no small mystery: if the comet fragments are
impacting Jupiter near its South Pole, then why would there be two
bright auroral spots near the North Pole? They are further south than
any other North Pole auroras have ever been observed. How did they get there?
Renee Prange has some theories, so now it's her turn
to hold forth for a while. She has already stated that Jupiter acts like a
giant magnet, as does the Earth. Any magnet has a north pole and a south pole,
and magnetic field lines pass through a magnet from its south pole to its north
pole. But they don't just stop there; they arc through space from one pole to
the other, completing a loop.
Renee's theory is that charged particles from the comet
fragments have been propelled along the magnetic field lines from their origins
near the South Pole all the way around to a corresponding latitude in the North
Pole region. "Some material from the comet itself was liberated at the South
Pole, accelerated ... around these magnetic field lines, and fell into the
northern hemisphere," Renee theorizes. A third image is shown that
illustrates these hypothetical magnetic field lines.
"I think it's a major discovery," Renee asserts.
Less scientifically intriguing but even more exciting to me is
the latest news from the amateur astronomy world. The impact spots on Jupiter
can definitely be seen now from amateur telescopes!
David Levy introduces this topic by commenting that it
almost feels as if they are all competing in some sort of contest to come up
with the biggest surprise of the week.
"I can't say that the fact that these dark spots are
visible for virtually everybody to see is the biggest surprise," he
says humbly, eyes alight with happiness, "but it sure is one of the
biggest ...
"Nobody expected this."
"We have some very large spots on Jupiter,"
David amplifies. "By now there are enough of these spots that no matter
where you are, when Jupiter is in the sky after dark, you will probably be
seeing some spots." He notes that Clark Chapman has been observing Jupiter
for many years, and he paraphrases Chapman's label of the Fragment G impact site
as "the most obvious feature ever to appear on this planet." According
to Levy, Chapman has challenged everyone on the Internet to argue that claim. "So
far, nobody has!" Levy notes happily.
"If you have any experience at all looking at
Jupiter," says David, "these spots should be extremely easy to
see."
Levy wonders what might have happened had the comet
fragments not been discovered ahead of time. "If the comet had never been
found," he muses, "right now, people would be seeing one spot after
another appearing on Jupiter." If it were just one spot, observers might
have guessed that a large object had hit the planet. "But these spots are
now forming all over that area of Jupiter," David points out, and if
anyone had dared to suggest that it was a series of separate impacts, others
would have responded, "No, how could you possibly get so many
impacts in the course of a week?"
Lucy responds generously. "I think we're lucky that
these guys were watching and found it!" she says, alluding to David and
the absent Shoemakers.
"If there has ever been a time to get out with a
small telescope and look at Jupiter -- ever since Galileo first observed
Jupiter through a telescope in 1610 -- this is the time to do it!"
David proclaims.
"This is just a marvelous time to be looking at
Jupiter!"
Lucy leads the rest of the news summary, which includes
additional images of Jupiter at different wavelengths, with impact spots
clearly visible.
Before presenting the latest report from the Kuiper Airborne
Observatory, Lucy describes the aircraft for us. A C-141 cargo plane that flies
at 41,000 feet, it has a compartment with a 36-inch telescope in it that can be
aimed through an opening in its fuselage. According to Lucy, "everyone
who's flown on it reports an exciting adventure."
"At 41,000 feet, they have oxygen within reach,"
Lucy enlarges. "[If] the interlock between the telescope and the observers
breaks, they have fifteen seconds to get their oxygen masks on."
One obvious advantage of this observatory is that it can fly
to wherever on Earth it is needed -- currently Melbourne, Australia. Dr. Gordon
Bjoraker of the Goddard Space Flight Center reports from Melbourne that another
advantage is that "you're flying above 99.9% of the water vapor in the Earth's
atmosphere, and you're above 80% of the total atmosphere.
"Our key thermometer is the methane molecule, which is
present in the Earth's atmosphere," Bjoraker adds. "By flying at
41,000 feet, this opens up a window where we can measure very strong methane
features on Jupiter that are not measurable from ground-based telescopes."
Dr. Anita Cochran of the University of Texas tells how she
and her colleagues at the McDonald Observatory in Fort Davis, Texas, had a ball
looking at Jupiter last night under outstanding observing conditions. "We've
mostly been running around like giddy little kids, because it's very
exciting to watch this," she confesses. "We've all had to take our
turns looking through the eyepiece, because you can see the structure of
the spots in the eyepiece ... and it's so much fun to watch Jupiter change [before]
our eyes!"
They did manage to take pictures of the Fragment L and
other impact sites. "The conditions turned spectacular very soon on, we
had excellent, excellent transparency almost all night and extremely
stable atmospheric conditions," she says. As a result, they obtained some
"really pretty images" using the 2.7-meter (8.8-foot) and 0.8-meter (2.62-foot)
telescopes.
One striking image that Anita presents shows four spots plus
the Great Red Spot; it was taken with the infrared camera in a "hydrogen
molecular band."
"We sent this in the conventional orientation,"
Anita notes, then adds, "We find it amusing to turn this and some of the
other images upside-down and look at it. You'll see why when you see the
image."
The image is inverted as she speaks, and a goofy-looking
smiley-face appears! Laughter is heard from the panelists.
"You turn it upside-down, and Jupiter doesn't seem so
unhappy, after all!" Steve later remarks.
Near the end of the question
and answer session, a reporter from Florida Today asks if there's any
evidence that the spots are fading. "We're going to ask Lucy McFadden to
answer that," Steve directs, "because Dave Levy was called away; he
is in great demand!" Sure enough, Levy has vanished from the set.
"There is evidence of fading of some of the spots,
changes in the brightness of some of the spots," Lucy acknowledges.
My pulse quickens at the thought of all those spots dimming.
Apparently it wasn't enough to buy a telescope; now I need the weather
to cooperate! A nice, clear observing window like the one they've been enjoying
in Texas would be wonderful ... and soon, before all those magnificent
spots fade away!
