__________________________________________________________________________ T H E O L E R O E M E R M E S S E N G E R _______________________________________________ JJJJ C G JJJJJJ I E JJJJ __________________________________________________________________________ Newsletter of the International Jupiter Watch Satellite Discipline E-mail issue 10 June 8, 1994 Editor and Discipline Leader: John Spencer Voice: (602) 774-3358 Lowell Observatory Fax: (602) 774-6296 1400 W. Mars Hill Rd. Internet: spencer@lowell.edu Flagstaff, AZ 86001 ----------------------------------------------------------------------- IO "OUTBURST" No new observations yet of the bright outburst of Io seen by Schneider, Sauter, and Spencer at the IRTF on 1994/05/30 in Jupiter eclipse. There is some hope of determining a location for the outburst from images that we took at the time, as we have L-filter images in sunlight which appear to show the hot spot against the sunlit disk, but deconvolution will be necessary to get the spot location. Jay Goguen points out that the (hot spot flux)/(reflected sunlight flux) for this outburst at 3.5 microns is similar to the ratio for the winter 1991 Loki brightening at 3.8 microns, so this outburst is somewhat brighter than the 1991 Loki brightening (because of the shorter wavelength), and much less bright than the 1986 and 1990 outbursts seen by Johnson, Veeder, and co. As the 1991 Loki event lasted about 3 months Jay suggests that this event may be equally long-lived, giving us a chance for more observations. Let's hope he's right! The new event is *probably* not at Loki, as Loki was close to the limb at the time of the observations and visual inspection of the resolved images suggests a southern hemisphere source. ------------------------------------------------------------------------ O2 ON GANYMEDE (!) Wendy Calvin has identified the mysterious 5773 and 6275 Angstrom absorption bands on Ganymede, found by Spencer and Calvin in 1993. They are due to oxygen molecules in contact with one another, and are prominent in the spectrum of solid oxygen frost (e.g., Landau et al. 1962, Spectrochimica Acta 18, 1-19). The location, intensity, and shape of the bands are matched so well that there is no doubt about the identification. Ganymede is much too warm for oxygen frost, so the features must be produced by clusters of O2 molecules trapped in the surface somehow. More later... ------------------------------------------------------------------------ UV GALILEAN SATELLITE OBSERVATIONS & REQUEST FOR HST 16 CYG B SPECTRA Lonne Lane (alane@jplal2.DNET.NASA.GOV) writes: Deborah Domingue and I had a very successful run on the 2.24m at MKO; very good Galilean satellite data from 294.6 to 347.3 nm. Generally good SNR; Ganymede looks about the same as it did with IUE in the period 1979-85. Europa and Callisto seem different -- need to better understand calibration before we can say anything positive. Did get good spectra of 16 Cygni B for comparison. Now doing a detailed comparison of its spectra with those acquired from Moon and other solar system bodies. Do you know of anyone who has 16 Cyg B from Hubble in range given above?? I have IUE data which was resampled on 0.2 nm centers, from the low resolution 0.7 - 0.8 nm channel. Would like better if I can find it because UVSI recorded data at 0.05 nm/pixel with a resolution of 0.12 and 0.3 nm. ------------------------------------------------------------------------- HST UV IMAGING OF IO John Clarke (clarke@sunshine.sprl.umich.edu) writes: We have part of our WFPC 2 far-UV imaging of Io now scheduled: 7 June 1994 11:33 to 15:33 UT: WFPC 2 far-UV imaging of Io airglow emissions 18 June 1994 at 1:45 UT start: near-UV WFPC 2 image series As we have discussed before, there would be a great advantage if any ground- based observers could observe Io thermal emission near the time of our HST images. Our images will be near west elongation, so observing should be straight forward if telescopes are available. No news yet on the June 7 observations ------------------------------------------------------------------------- SEARCH FOR NEUTRAL SULFUR ON IO AT 1 MICRON Schneider, Sauter, and Spencer obtained high S/N, high spectral resolution, spectra of Io at 1.08 microns with CSHELL at the IRTF on May 26 and 30 UT, to look for emission by neutral sulfur. Spectra were taken in Jupiter eclipse and in sunlight. No emission was immediately apparent but something may show up with further analysis. ------------------------------------------------------------------------- OBSERVING PLANS Bob Howell will be continuing 3-5 micron speckle photometry of Io in Wyoming on June 18 - June 24. Spencer will again use NSFCAM on the IRTF to monitor the Io volcanism in Jupiter eclipse on June 19 and 21. -------------------------------------------------------------------------- UPCOMING CONFERENCES DPS Abstracts are due July 1st! ------------------------------------------------------------------------- PUBLICATIONS IN (OR EMERGED FROM) THE PIPELINE I haven't had time to update this list, though there are quite a few new publications out there. Hopefully the next issue will have an updated list. Send me information on any preprints! ----------------------------------------------------------------------- COMET CRASH UPDATE- NEW PREDICTIONS Here are the latest impact time predictions, from Chodas and Yeomans: Predictions as of 1994 June 3 Date of last astrometric data in these solutions: 1994 June 1 {This is a shorter version of our earlier table; we plan to issue this version more frequently than the full version.} The predictions for all fragments except Q2 are based on independent orbit solutions; the orbit reference identifier is given in the rightmost column. The orbit solution for fragment Q2 was obtained by applying a disruption model to the orbit for Q1, and using astrometric measurements of Q2 relative to Q1. Immediately to the right of the predicted impact times, we give the 1-sigma uncertainties in those times for all fragments except Q2. We have made an effort to make these uncertainties realistic: they are not formal uncertainty values. NOTE: To obtain a 95% confidence level, one should use a +/- 2 sigma window around the predicted impact time. The uncertainties for fragment Q2 have not been quantified, but are probably comparable to those for P2. The dynamical model used for the predictions includes perturbations due to the Sun, planets, Galilean satellites and the oblateness of Jupiter. The planetary ephemeris used was DE245. ---------------------------------------------------------------- Fragment Impact 1-sig Jovicentric Meridian Angle Date/Time Unc. Lat. Long. Angle E-J-F Orbit July (UT) (min) (deg) (deg) (deg) (deg) Ref. ---------------h--m--------------------------------------------- A = 21 16 19:55 26 -43.23 176 63.56 99.35 A10 B = 20 17 03:07 23 -43.45 77 63.67 99.22 B11 C = 19 17 06:59 24 -43.33 217 64.53 98.64 C8 D = 18 17 11:18 28 -43.34 14 63.49 99.36 D9 E = 17 17 15:30 17 -43.70 164 66.13 97.41 E25 F = 16 18 00:40 23 -43.79 139 64.17 98.77 F16 G = 15 18 07:52 16 -43.80 37 66.99 96.77 G25 H = 14 18 19:47 16 -43.86 109 67.32 96.52 H23 K = 12 19 10:39 16 -43.96 287 68.15 95.90 K24 L = 11 19 22:40 16 -44.07 2 68.95 95.31 L25 N = 9 20 10:21 26 -44.59 67 67.13 96.49 N12 P2= 8b 20 15:27 25 -44.82 253 66.46 96.91 P11 Q2= 7b 20 19:49 -44.48 48 69.27 95.00 Q1= 7a 20 20:16 15 -44.20 64 69.69 94.75 Q27 R = 6 21 05:59 19 -44.27 57 70.24 94.34 R22 S = 5 21 15:46 17 -44.26 51 70.76 93.97 S32 T = 4 21 18:16 44 -45.28 145 67.43 96.14 T7 U = 3 22 00:25 85 -45.19 3 71.74 93.15 U6 V = 2 22 04:06 31 -44.52 141 68.16 95.77 V8 W = 1 22 08:34 19 -44.29 299 71.32 93.57 W25 Notes: 1. Fragments J=13 and M=10 are omitted because they have faded from view. Fragments P=8 and Q=7 each consist of multiple components. The March'94 HST image shows that P1=8a has almost completely faded away (so it too is omitted from the Table), and that P2=8b has split. We do not as yet have sufficient data to obtain independent predictions for the two components of P2=8b. 2. The impact date/time is the time the impact would be seen at the Earth (if the limb of Jupiter were not in the way); the date is the day in July 1994; the time is given as hours and minutes of Universal Time. 3. The impact latitude is Jovicentric (latitude measured at the center of Jupiter); the Jovigraphic latitudes are about 3.84 deg more negative. 4. The impact longitude is in System III, measured westwards on the planet. 5. The meridian angle is the Jovicentric longitude of impact measured from the midnight meridian towards the morning terminator. This relative longitude is known much more accurately than the absolute longitude. 6. Angle E-J-F is the Earth-Jupiter-Fragment angle at impact; values greater than 90 deg indicate a farside impact. All impacts will be just on the farside as viewed from Earth; later impacts are closer to the limb. -------------------------------------------------------------------------- MORE SL9 NEWS From the bulletin board: 01 Jun 1994: D. Jewitt and N. Trentham report that nucleus 15=G is double. See "observ/results/iauc5999" PERIODIC COMET SHOEMAKER-LEVY 9 (1993e) D. Jewitt and N. Trentham, University of Hawaii, communicate: "New observations from the University of Hawaii 2.2-m telescope show that nucleus 15 (= G) is double. On May 7 UT, the fainter component (15b) appears 3".5 east and 3".7 north of the brighter (15a). The red magnitude difference measured in a 1"-radius aperture is 3.8. The fainter component is not evident in observations taken in previous months under similar observing conditions." Note that the March HST image is reproduced in the July Sky and Telescope issue- I for one had not seen it before. ---------------------------------------------------------------------------