February and March 2016
After the terrible winter weather experienced in December and January it was very refreshing to see so many observations arriving in February and March as a period of settled weather brought some clearer and steadier skies to the UK. Jupiter was the main target for this period, and this was only to be expected given that the giant-planet reached opposition on the 8th of March and was observable from dusk until dawn for much of the period. Mars and Saturn were improving through this period but were still not well placed, being both rather low for detailed observation; however both were observed and imaged in the period with excellent results.
Starting with Jupiter, readers may recall that in the last period there was a noticeable thickening of the North Equatorial Belt (NEB) which seemed to originate from the large storm White Spot Zulu (WSZ) and had spread around half the circumference of the planet. Further thickening was expected in February and March but this didn’t happen; instead WSZ looked almost like a rolling pin acting on the thicker part of the NEB and squeezing out a thinner turbulent region prograde of it. The northern edge of the NEB was particularly disturbed and there was an indistinct Temperate Belt structure visible over only parts of the circumference. In the south there was a large empty South Tropical Zone (STrZ) and the South Temperate Belt system (STB) was only visible in its southern-most aspect with Oval BA being very pale and hard to observe; small white-oval storms deep in the southern hemisphere were very prominent and obvious on the edge of the polar region.
Observations started on the third of February with images from Dave Finnigan showing the southern white oval storm systems and one faint festoon in the EZ growing from a dark barge on the southern edge of the NEB. His image also shows a dark edge, almost a separate thin belt, at the southern extreme of the SEB and extending a little way around the socket in the belt containing the Great Red Spot (GRS). This dark edge gives the SEB a bifurcated appearance, something that remained obvious throughout the period. Carl Bowron’s images from the 10th of Feb’ also show this very clearly and show the narrowest and most disturbed part of the NEB covering most of the visible hemisphere. Steve Norrie added images on the 13th of Feb’, the first of an excellent sequence of images from Steve through this reporting period. They show the development or extension of the dark bifurcation in the SEB extending around the GRS socket and giving the spot a definite ‘eyebrow’.
Images from Carl and from Paul Crossland around mid-month confirmed this feature while Steve and I caught Io in transit, together with its shadow on the 22nd of February.
On the 24th
Martin Lewis submitted an image taken with an ASI174 colour camera showing great detail and the point where the NEB expanded in a gentle step near the dark root of faint festoons, well prograde of WSZ. A faint North-North Temperate Belt (NNTB) is visible in his image with some dark concentrations towards the North Polar Region (NPR). Martin also submitted a methane band image taken at almost the same time. Methane filters are rather interesting. Jupiter is made of a complex mix of gasses but hydrogen does predominate. Where there is methane (CH4) in the atmosphere it absorbs sunlight at a frequency around 890 nanometres, a region in the near infra-red well beyond the sensitivity of human eyes, while the surrounding gasses reflect the light. The result of using a methane filter is to show as dark spots and bands the region where methane is most common at the top of the Jovian atmosphere.
The EZ is often very bright in these filters, showing a thin high haze of cloud covering the deeper regions where dark festoons might otherwise be visible. When these hazes clear, or thin, we see detail in the EZ and hints of equatorial belts. I think Martin’s image is the first methane image I have received from an SPA member but was not the last to arrive in the period; more of which shortly! A colour image from Steve Norrie, taken around 45 minutes before Martin’s methane image, shows some of the same dark features as concentrations on the edge of the NEB and provides an interesting contrast between broad and narrow-band images of this subject; Steve’s image also shows a hint of Oval BA rotating off the planetary limb as a pale and ‘washed-out’ feature. It is a shame this same feature had rotated out of view when the methane image was taken as both the GRS and Oval BA are known to be obvious bright features as these storms force large amount of ammonia ice crystals to the top of the atmosphere which are highly reflective in the methane band.
Alexei Pace, imaging from Malta, submitted an image on the 25th of Feb’ showing that the banding in the SEB extended over much of the planet with two obvious darker and two fainter brown bands comprising the wider SEB system, while more images from Steve on the 27th showed an almost identical scene. On the 28th, both Carl Bowron and Paul Crossland submitted observations showing the isolation of the GRS and the extension of the ‘eyebrow’ feature, described above, around the full length of the socket holding the GRS. Carl’s image shows this in great detail and also catches some of the WSZ as it ‘rolls-out’ the NEB in this region.
Finally I must mention visual observations sent in by Matthew Barrett from the 11th, 12th, 19th and 24th of the month using a mix of red and yellow eyepiece filter to pick out detail. Matthew pays careful attention to variations in regional brightness intensities and his sketches can be used to help quantify the variations in brightness seen in images from differing cameras and taken through varying instruments. Dale Holt also submitted an excellent drawing of Jupiter made at the end of January as a ‘late submission’ to the section.
Moving into March and on the 4th Alexei Pace sent in an image showing the first clear view of Oval BA for this period. This storm is no longer a very obvious feature as the dark annulus that previously surrounded it has now faded. A number of dark concentrations precede and follow it which helps to locate it but the spot itself is a very pale ruddy colour and no longer rivals the GRS; at least, not in visible light, in the infra-red this feature is much more obvious. Images taken by Steve Norrie on the 7th and by myself on the same night confirm this impression. Paul Crossland sent in some 19 images showing the rotation of Jupiter from the 7th into the 8th of March giving the fullest coverage of Jupiter for the night of opposition itself. Over midnight the moons Europa and Io transited Jupiter and Paul caught the shadow of Europa on Jupiter sitting almost exactly under the disc of the moon, demonstrating the alignment of Sun, Earth and Jupiter at opposition.
Alexei Pace, Martin Lewis and Ian Sharp also caught these aligned-shadow events in the early hours of the 8th and Martin also sent outstanding IR images, extremely detailed, along with more methane band images in which the transiting moons stand out very brightly. Simon Kidd sent an image from the 12th showing a similar aspect to images submitted by Graham Taylor, taken back on the 5th with a small Vixen 110mm telescope. Graham feared his results were “more Damien Hirst then Damian Peach!” but the comparison is useful. Simon’s detailed image shows much more than Graham’s image but the overall structure is still visible even if the absolute resolution is not; small telescopes can make a contribution to this work.
Looking now at the GRS, Steve Norrie sent images from the 6th, 7th and 14th showing the extension of the eyebrow feature around the socket in the SEB and the emptiness of the STrZ around the spot itself. He also picks out the very turbulent region within the SEB, visible as a series of distorted white ovals, following in the wake of the GRS. The spot itself is fairly uniform with only a slightly darker annulus and a small dark concentration at its centre. Dave Finnegan’s excellent image from the 13th confirms this impression and shows slightly more detail in the spot, while an image taken by Paul Crossland slightly earlier hints at concentrations on the rim of the GRS and also shows very clearly how the northern storm WSZ is distorting and redirecting flow within the NEB. WSZ has often been a difficult feature to observe being, by nature, a white storm in a white belt, but this apparition it has made itself very obvious, rivalling or exceeding Oval BA in size and activity; it is currently the second most obvious spot-feature on Jupiter. Alexei Pace’s image from the 14th confirms this and also shows the turbulence region behind the GRS in exquisite detail.
The next clear period covered the nights of the 16th to 18th of March which brought another rush of contributions from Paul Crossland, Larry Todd, Carl Bowron, Dave Finnigan, Alexei Pace and Martin Lewis with both Alexei and Martin adding more Methane images to the more usual colour ones. A number of moon and shadow transit events were observed and it was very noticeable how far north the shadows of the outer moons have migrated compared with last opposition when they were aligned with the equator of Jupiter; Carl’s image of Callisto in transit shows the moon on the extreme northern limb, scraping past the North Pole. Alexei and Martins’ images from the same night are extremely detailed showing large festoon activity in the EZ, something that had been only faint and unclear earlier in the period and was also caught by Dave that same evening; Martin even caught albedo features on Callisto itself. Both methane images show some detail in the EZ suggesting that the thin high reflective cloud over this region has started to clear.
With space running out I must move on to other planets. Larry Todd sent in images of Mars from the 13th
of February and the 8th
of March. Alexei Pace also imaged Mars on the 13th
of March and this provides us with a sequence in which the steady growth in apparent size of the planet is evident, through the period, as Mars moves towards opposition in May. For such a low elevation target surface detail is impressive and shows that modern cameras can catch significant detail even when Mars is below 10 arc-seconds in apparent size. Major surface albedo features are clearly seen and are identifiable along with cloud features over high-ground, notably over the Elysium region and Olympus Mons. The small north polar cap is visible as are the dark regions surrounding it. Syrtis Major is very obvious and the southern Hellas Basin is still full of frost and cloud, not yet melted away as the southern hemisphere moves into springtime. Alexei also sent in a sharp image of Saturn with some colour fringing as might be expected from its low altitude but with banding on the disc and excellent detail in the ring system.
Finally I must thank Tony Ireland for his tongue-in-cheek contribution of the recent internet-controversy caused by the publication of an amateur Jupiter image showing what looks like a rather obvious lens-flare, to one side near the moon Europa. This is taken as “proof” of an extra-terrestrial “mother ship” in orbit around the planet. Since the mothership is around one third the size of Jupiter and appears in no other images I am tempted to repeat a phrase often used by Sir Patrick Moore in connection with astrology and other pseudo-science. “There is one born every minute!”
I must apologise in that this report is incomplete. I went on holiday in the last week of March and had to create this report in time for a publishing deadline tied to the SPA magazine; as a result I wrote the report before leaving for holiday and it misses out on a number of excellent observations made by members in late March. These observations will be bundled into the next section report and I hope no members of the section will mind this tardiness on my behalf.
Thank you for your contributions and do please keep them coming.