| Jupiter in 2009: An interim report by John H.Rogers |
Jupiter in 2009: An interim report
Jupiter in conjunction with Neptune:This occurred three times in 2009: on May 25, July 13, and Dec.20. The May conjunction was imaged by David Arditti (Fig.1) and Bernd Gahrken. They saw just what Galileo had drawn on 1612 Dec.28 and 1613 Jan.27.
Occultation of bright star:
Jupiter occulted the 6th-mag star 45 Cap on the night of August 3/4: the brightest such occultation since 1971. Several observers in Europe recorded time-lapse videos of the event, which show one or more dramatic flashes of the star for several minutes as it passed through the atmosphere of Jupiterfs south polar region before it disappeared. Such flashes have been notable at previous occultations, but this time some videos show them exceeding the starfs normal magnitude. Unfortunately it is not always clear how the brightness has been affected by image processing, and we have had no visual reports of the event. Videos have been posted by
Maurice Toet and John Sussenbach (Netherlands), and Marc Delcroix (France). Delcroixfs are the most detailed recordings, at:
http://astrosurf.com/delcroix/occ_20090803_Jupiter_45Cap-MDe.htm.
Opposition, equinox, and satellite phenomena:
Jupiterfs opposition was at 15 deg.S, in Capricornus, on 2009 August 14. (Coincidentally, this happened just after Saturnfs equinox on August 11.) Jupiter also passed through equinox this year, on 2009 June 23, and the Earth passed through Jupiterfs equatorial plane on 2009 April 15. Therefore, there are mutual phenomena of the galilean moons throughout this year, and for the first time, several observers have made resolved time-lapse videos of these events.
The low inclination also means that all the satellites and their shadows transit in the equatorial zone. A spectacular multiple phenomenon occurred on Aug.12: simultaneous transits of Ganymede and Europa and their shadows, while Io entered eclipse (Fig.2) This was a neat illustration of the orbital coupling between these three moons ? as was the fact that it recurred a week later (after opposition, so the shadow positions were reversed) (Fig.3). Both events were widely observed across Europe and beyond. (Fig.3 does not include the superb series of images by Dave Tyler and Jose Antonio Soldevilla individually on Aug.19/20).
The eBird Strikef:
The new impact on July 19, discovered by Anthony Wesley, at 57 deg.S, has been described in our interim reports to the end of July. Fig.4 shows a small selection of hi-res images in August. As of Aug.26, the dark impact scar had largely faded and dispersed, but two or more oblique dark streaks remain, with their Np. ends clearly being entrained by the prograding jet at 53 deg.S. On Aug.29 Joel Warren reported with his images: gWesley's impact is rapidly
fading .... just a pale blemish. Easiest to see on the limbs, and you have to know what to look for the closer it gets to the CM.h A full report will appear soon in the Journal of the BAA. Meanwhile, two other web sites are essential viewing: 1. Graphic display of the development of the impact site, in animated polar projection maps, by Hans-Joerg Mettig and Theo Ramakers: http://www.ceastronomy.org/gallery/main.php?g2_itemId=6848 2. The Hawaiian rock version, g1994 (The Jupiter Impact of 2009)h, by Kelly Fast: http://www.youtube.com/watch?v=Ie_eiv4zzxk Jupiterfs atmosphere Jupiter of course continues to display its grand meteorological phenomena. Many observes are now sending superb hi-res images. These include not only the observers in Australia, Brazil, and the Philippines who have been the mainstay of hi-res coverage for the last 2 years (plus excellent new observers in Australia: Trevor Barry and Darryl Pfizner Milika), but also more northerly observers such as Don Parker (USA), Brian Combs (USA), Efrain Morales Rivera (Puerto Rico), Paulo Casquinha (Portugal), Paolo Lazzarotti (Italy), and Jean-Jacques Poupeau (France). Fig.5 is a set of images covering the whole planet on Aug.13-14; equally good or better sets could be prepared from other images on Aug.12-13 or 18-20, including more from the above-named observers. (Also, images at intervals of 1-3 rotations on Aug.12-14 by Parker, Barry, Casquinha and Akutsu allow the currents and jets to be seen by eblinkingf between the images.) Overall, the planet has been recovering from the global upheaval of 2007, and many regions show no large-scale activity. However, the SEB is beginning to fade again in preparation for another cycle of fading and revival; and the NEB has begun a new cycle of expansion northwards. Here is a quick preliminary summary of some interesting features, which are identified on Fig.5 (This does not yet include any analysis of the JUPOS data.)
SPR to SSTB:
Long-lived anticyclonic white ovals (AWOs) are now familiar features in v-hi-res images in each of the four domains from ~60 deg.S to 40.5 deg.S. A new analysis of BAA and JUPOS records indicates that the AWO at ~60 deg.S, which is usually slightly reddish, has probably existed since 1994 or earlier [Rogers, Adamoli & Mettig, submitted to JBAA].
STZ/STB:
The next AWO to the north, oval BA, was reddish from 2006 to 2008 but has almost no colour in 2009. The formerly orange ring within it is now the same pale fawn colour as its surroundings.
The STB is tenuous at most longitudes, as usual, but has developed a new dark sector, which is f. the GRS and due to pass the GRS later this year (marked eSTB-1f on Fig.5). This has developed in a long gap, opened up by the convergence of the other two long-lived STB sectors: the short, very dark block f. oval BA (eSTB-2f on Fig.5), and the long, very pale blue eSTB Remnantf. The STB Remnant itself formed in identical circumstances in 2004-05 [http://www.britastro.org/jupiter/2006report07.htm and ...report11.htm].
Images this year give more evidence that it is a cyclonic cell: its darkness in methane-band images, and its sinuous blue outline in an exceptionally fine image by A. Wesley on Aug.4 (Fig.6).
SEB & GRS:
The GRS is at L2 = 138.
Switchoff of SEB activity: There was still dense bright rift activity f. the GRS in March-April. The rift activity ended rather abruptly in early June; indeed there may have been no new rifts since May, and the residual rifted region disappeared when its f. end reached the GRS. The earchf connecting the GRS rim with the SEBs f. it faded away at the start of July, leaving the GRS as an isolated though pale oval (Fig.7). Several observers therefore predicted that the switchoff of activity would lead to SEB fading again. Indeed, in August the SEB seems to be generally fading, and barges in it are strikingly dark. So we can expect the fading to continue until a SEB Revival outbreak begins some time in 2010 or 2011.
SEBn:
The SED was very inconspicuous in early 2009, but was identified as a bright strip at L1 ~ 35 which passed the GRS on July 8. In mid-August it has partially recovered its classic form, though still very elongated, (L1 ~ 95, Aug.13) (Fig.5), as it approaches the GRS again.
The EZ is still largely white, with no major festoons nor EB, but hi-res images reveal an intricate network of innumerable faint bluish streaks.
There are still only a few large projections on NEBs.
NEB/NTropZ:
This has been the scene of the greatest activity this year. In the spring, there were examples of small bright spots appearing in the NEB and expanding into distinct rifts, as in 2008. But in the summer the rifting expanded to an exceptional extent, covering the full width and much of the circumference of the belt. Although it has always been difficult to establish any relationship between NEB rifting and other phenomena, it may well be associated with the NEBn expansion event that is now beginning.
This event began on May 31 when the Sf. end of a large rifted region, passing a NEBn projection which marked the location of a previously visible dark barge, flipped dark material into the NTropZ. (This was at L2 = 136, due N of the GRS: Fig.7. See previous bulletins; the following analysis has been done by Michel Jacquesson.) Three very dark spots in succession appeared at this point and prograded in the NTropZ, but then drifted S again and reversed or halted their drift. Spots 2 and 3 remain, at L2 = 98 and 118: these are like anticyclonic Little Brown Spots which have appeared in early stages of previous NEB expansion events. In August, the region around them has turned a dusky yellowish colour ? clearly the start of the expansion event. At its f. edge is a bright white spot (arbitrarily labelled WSY on Fig.5).
On Aug.7, at L2 = 20, a second such outbreak began in exactly the same way (Fig.6), with the Sf. end of a bright rift flipping around a little red barge (spectacularly shown in Wesleyfs image on Aug.4) to create a dark brown ring in the NTropZ, which prograded at -40 deg/month for a week, then halted at L2 = 7. With turbulence continuing to project into the NTropZ at the original longitude as well, this too seems sure to be a continuing focus of NEBn expansion, and others could yet appear.
Meanwhile NTropZ white spot Z ? now 12 years old, still very bright and rapidly prograding ? has approached the first NEBn outbreak, and is now positioned just f. white spot Y (Fig.5).
NTB/NTZ:
The NTB is still broad and orange after its dramatic revival in 2007. The N edge is still very sinuous, and embedded within it are some very dark grey streaks and some small reddish spots. In one or more sectors the disturbance seems to spread N across the NTZ forming a eN. Temperate Disturbancef ? which would confirm last yearfs conjecture that such features are a delayed sequel to vigorous NTB revivals. We have not yet analysed these in detail, and an objective of this yearfs v-hi-res campaign will be to determine the movements of spots in and around these sectors, to see if they interrupt the jetstreams.
NNTB/NNTZ:
The most notable feature is the Little Red Spot in the NNTZ. This year it has been exceptionally red. Initially it was an isolated red spot, as the NNTB was absent there, but then various dark spots and streaks gathered around it, and now it has a dark rim with NNTB adjacent, while the interior is still red. Our analysis of BAA and JUPOS records indicates that this LRS has existed at least since 1993 [Rogers, Adamoli & Mettig, submitted to JBAA].
John Rogers, 2009 Aug.28
_________________________________ John H. Rogers, Ph.D. Jupiter Section Director, British Astronomical Association. http://www.britastro.org/jupiter _________________________________ Fig.1Fig.2
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John H. Rogers,Ph.D. Jupiter Section Director, [British Astronomical Association.]
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