Io and Europa Atmosphere
and Io Torus Detection Through
Occultations and Conjunctions
2010 Annual IOTA Meeting
December 3-5, 2010
Boston, MA area
Scott Degenhardt
International Occultation Timing Association
scotty@scottysmightymini.com
Having purchased this after attending the
2009 Society for Astronomical Sciences Conference,
I hatched some hair brained ideas….
Scotty’s logic:
If…..
1 lightcurve data point = a picture into a distant place
and
1 picture = 1000 words
then
1000 data point lightcurve X 1000 words = 1,000,000 words!!!
1 miniDV tape ~ 1 hour of video data
So…
Therefore!!!
Double Jupiter Mutual Event of Aug 7, 2009
Io’s shadow eclipses Europa
23 minutes later Io occults Europa
Io
Europa
• An anomalous trend was detected in the 20090807 IoII.
• Theories were proposed for possible sources of this anomaly.
• Possible sources fell into 4 main categories:
1. Camera response
2. Recording method
3. Reduction method
4. Extinction via Io’s atmosphere
• Experiments were designed to validate or refute each.
• Using a model derived from the 20090807 lightcurve predictions of
atmospheric extinction were created for the upcoming 20090901 IoII, which
did repeat the anomaly as predicted based on that atmospheric model.
Europa’s
motion
brightening
Io
dimming
Europa
3.6” = 6 Io radii
IAEP (Io Atmospheric Extinction Project) was launched,
a global plea for observations was made.
IAEP RESULTS WERE PUBLISHED AND PRESENTED:
Degenhardt, S. et. al (2010),
Io and Europa Atmosphere Detection through Jovian Mutual Events,
The Society for Astronomical Sciences:
Proceedings for the 29th Annual Symposium on Telescope Science, p. 91-100
http://scottysmightymini.com/IAEP/SAS2010_Io_Europa_Degenhardt.doc
YouTube video in four parts of the SAS 2010 Power Point Presentation:
Part 1: http://www.youtube.com/watch?v=LJE_V9Jysto
Part 2: http://www.youtube.com/watch?v=0BFRpbTc748
Part 3: http://www.youtube.com/watch?v=02s4KIZ55NE
Part 4: http://www.youtube.com/watch?v=UECOxlFKLVI
IAEP results:
11 observers
4 countries
53 data sets
28 individual events
Typical lightcurve for extended wing data:
 Io and Europa have dimmed intensity
trends surrounding the occultation. (We
dubbed this “lowered shoulders”)
Ganymede wing data displayed a
brightening intensity trend surrounding the
occultation. (We dubbed “raised shoulders”)
Simulation indicates “raised shoulders” to be the nominal
response to two merging intensities of near equal brightness.
raised shoulder = nonlinear camera response creating the non-flat wings.
preliminary investigation: source = region between the two airy disks
As the photons in the outer rings of the airy disks begin to overlap, previously
undetected photon rates become detectable due to the doubling of the
photon rate.
Photon Doubling Effect (PDE)
PDE region
(intensity above baseline
between merging spots)
baseline intensity
False color intensity profile of Io (left peak) and Europa (right peak)
A “light bridge” is clearly seen forming between the two merging spots
Preliminary wing trend conclusion
 PDE causes a nonlinear intensity increase as two airy
disks of near equal intensity merge resulting in raised
shoulders.
 Raised shoulders should be the nominal response for
two merging intensities of near equal brightness.
 Therefore lowered shoulders indicate an anomalous
loss of intensity in the measurement aperture.
Now we need to identify the source of the loss of light…
This data analysis technique of the raw video intensity effectively single
handedly eliminates nonlinear camera response, recording method, and
reduction technique as the source of lowered shoulders.
Europa (behind Io) experiences dimming as it nears Io.
Two photometry methods used:
Individual photometry:
A measurement aperture is placed on each moon
individually. Individual intensities are normalized to a
common moon.
Combined photometry:
One large aperture
surrounds both target
moons. Total intensity of
the large measurement
aperture is normalized to a
common moon.
Possible sources fell into 4 main categories:
1. Camera response
2. Recording method
3. Reduction method
4. Extinction via Io’s atmosphere
Dimming source conclusion:
o The source of the dimming has been linked to the moon being occulted by
Io or Europa.
o The start of dimming and end of brightening defines boundaries of
extinctive material.
o Moons being occulted by Io suffer extinction of their light when they are
within 5 to 30 Io radii of Io.
o Moons being occulted by Europa suffer extinction within 22 to 30 Europa
radii of Europa.
o Moons being occulted by Ganymede do not suffer extinction at these
same distances.
o An asymmetry was noticed in the slope trend of the ingress/egress of
extinction in both Io and Europa lightcurves.
If Io was west of Jupiter and occulted a moon with its western limb:
Ingress/egress > 1
If Io was east of Jupiter and occulted a moon with its western limb:
Ingress/egress < 1
Conclusions on asymmetry of Io atmospheric extinction:
Occultations on Io’s Jupiter facing limb have longer extinction
slopes.
Longer extinction indicates more extinction material.
More extinction material on Io’s Jupiter facing limb possibly
implies a stream of material from Io towards Jupiter. This
comes as no surprise given that Jupiter is called the “vacuum
cleaner” of our solar system.
Why?
Why have these extinction events
been missed for 400 years…?
Likely due to insufficient wing data
surrounding Jupiter Mutual Events.
Lightcurve (b.) is the same event
as (a.), only (a.) has just 6 minutes
of wing data surrounding the
occultation (typical of what is found
in the NSDC IMCCE database).
How small can your system be?!
•20100104 UT marked the end of the JME cycle
•This was not the end of Jovian Extinction Events
•Occultation misses, i.e. conjunctions still provide
opportunities for extinction measurements
•Conjunctions remove the camera response
issues associated with merging spots.
Io’s eastern and western Torus tips appear more dense due to an optical
geometry where the Torus material is collimated to our line of sight.
Schematic of a Torus Jovian Extinction Event (TJEE)
Torus material
Io
160 Io radii
Collimated Torus material
at the tip of Torus
Torus of Io
(viewed from above)
Earth’s view
Data provided by Wayne Green
Io Spectra taken by
John Menke
HOW CAN I PARTICIPATE?
I see the following potential research that can be done now:
1. Detection of extinction through video recordings in modest equipment. Begin
making plans now to observe the next round of Jupiter Mutual Event
occultations in 2014.
2. PDE experiments to better our understanding of our observed nonlinear
intensity gain with merging spots.
3. Detection of Io or Europa atmosphere through transits by any
astrophotographer that carefully does his work.
4. Data mining of IMCCE NSDC lightcurves, Hubble, Voyager, Galileo, and Don
Parker images (just kidding Don!), all sorts of things to look for now that we
have pointed it out to everyone in the paper.
5. Jovian Extinction Event observations. Io Torus detection and modeling, and Io
and Europa atmosphere modeling through conjunctions.
6. Spectroscopy of Torus extinction events.
7. Think outside the box (or rather your box should have elastic walls and not
cement)!
You do not have to wait 4 years
(2014) for the next
Jupiter Mutual Event Cycle
to measure extinction!
Jovian Extinction Event predictions for 2010 are available here:
http://scottysmightymini.com/JEE/JEE.htm
scotty@scottysmightymini.com
Salvador Aguirre
Sonora, Mexico
Dave Clark
Texas, USA
Scott Degenhardt
Tennessee, USA
Tony George
Oregon, USA
Donald Parker
Florida, USA
Terry Redding
Florida, USA
Andy Scheck
Maryland, USA
Brad Timerson
New York, USA
Not pictured but submitting data sets:
Wayne Green – Colorado, USA
Mike Hoskinson – Alberta, Canada
John Menke – Maryland, USA
Roger Venable – Georgia, USA
FINAL CONCLUSION
• Dimming trends of Io and Europa occultations have been linked to
atmospheric extinction of the light of the moon being occulted.
• Asymmetries of the slope of extinction have been noted.
• No extinction trend has been detected for Ganymede.
• Extinction events caused by the Torus of Io and conjunctions with Io and
Europa are detectable, further validating the extinction hypothesis.
• A 3D model of these atmospheres should be possible by inverting the
lightcurves derived by our observational method.
• Extinction detection is possible in modest equipment. Further
photometric and spectroscopic data collection is a must to gain better
statistical data on the material causing the extinction phenomenon.
• Detection of extinctive material around our Jupiter may have implications
for other Jupiter like exoplanet research.