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The Sky Above You – May 2024

 

By Duncan Lunan

 

 

The Moon will be New on May 8th, and Full on May 23rd. The Moon passes Jupiter on the early evening of the 10th, and although it passes all the other normally visible planets, none of them will be visible. This month, unusually, there are no planets visible in the morning and evening sky, until the very end, when Saturn and Mars will be low in the morning sky on May 31st, with the waning Moon near Saturn. The Moon doesn’t even pass many bright stars, though it will be near Castor and Pollux in Gemini on the 12th, when at First Quarter (half-full, waxing) and very close to Antares in Scorpius when it’s Full on the 23rd.

 

In my book Children from the Sky (Mutus Liber, 2012). I discussed the event of June 18th, 1178 when, according to the chronicler Gervase of Canterbury, five or more men apparently witnessed the flare from an impact on the Farside of the Moon, forming the crater Giordano Bruno – 12 impacts in 30 minutes. Patrick Moore and H.P. Wilkins deduced the crater’s existence from the rays of impact debris, reaching the hemisphere facing Earth. Sydney Jordan produced a dramatic painting of it for my book.

 

The monks claimed to have seen ‘red sparks’ flying off from the Moon, and allegedly they couldn’t have seen ejecta at that distance. The crater was photographed by Clementine, Kayuga-Selene, and in detail by Lunar Reconnaissance Orbiter. The Kayuga-Selene images were used to estimate the age of the crater, by the number of smaller craters on the ejecta blanket immediately surrounding it, giving an age of approximately 4 million years, ‘much too old for the [1178] hypothesis’, says Wikipedia. But if the monks’ account is correct, and there were 12 impacts in rapid succession, then the ejecta from the multiple events would have been superimposed and it would make the main crater look much older. It had been suggested that the asteroid 1991 VG might have been blasted off the Moon by the impacts, and the same suggestion was made for another discovery, 1999 CG9. But in April 2016 an ‘Earth co-orbital’ was found in an orbit giving recurring encounters with the Earth, making it a ‘quasi-satellite’ (Dave Adalan, ‘Was asteroid Kamo’oalewa blasted from this moon crater?’, EarthSky, online, April 25th 2024). Orbital eccentricities suggest that it reached that position 1-10 million years ago, and spectral data suggests it’s of the same rock type as Giordano Bruno. We may know more soon, because the Chinese probe Tianwen-2 is scheduled to return samples from Kamo’oalewa within 2.5 years after its 2025 launch. We can also expected more accurate orbital data for it, from NASA’s NEO Surveyor telescope, to be launched in 2027. But we should keep in mind that Giordano Bruno is only the most likely, at present, out of a number of candidate craters.

 

Meanwhile, on the Moon, the Japanese SLIM lander has survived a third lunar night and renewed contact with Earth on April 24th. It wasn’t designed to survive lunar night at all, and doing so three times is all the more remarkable because it’s still nose-down, able to power up and send images and data only during the latter part of the lunar day. My guess is that because the heat loss during the night is due to radiation into space, the nose-down configuration may be preserving enough warmth to keep the lander alive. But that’s only a guess, and Japan’s engineers are working hard to find a full explanation, which no doubt we shall hear in due course.

 

The planet Mercury is invisible this month, even though it’s at maximum elongation from the Sun on the 9th.

 

Venus is still out of sight beyond the Sun, at conjunction on the far side of it during June.

 

Mars will rise about 4 a.m. at the end of May, so it’s not likely to be seen in Scotland’s pre-solstice twilight. After a long-drawn-out farewell, the Perseverance rover has finally lost touch with the stranded Ingenuity helicopter. The last transmission from Ingenuity was received on April 16th. Ingenuity has been sending to Earth via the Perseverance rover, and now that the helicopter is grounded with two broken rotor blades, the rover has moved out of range. Such moments have a chequered history: the USA’s first solar-powered satellite, Vanguard 1, made a nuisance of itself in 1958 because its job was done, it was using frequencies that were needed for its successors, and there was no way to turn it off. It was expected to remain in orbit for 2000 years, but fluctuations in upper atmosphere density reduced that to 240 years, and it finally fell silent after 6 years, to general relief.

 

Off-switches were routinely fitted to satellites later, but not always used as intended. The Phobus-1 probe was accidentally switched off on its way to Mars in 1988; Robert Farquhar ‘forgot’ to switch off International Comet Explorer at the end of its mission in 1986, so citizen scientists were able to reactivate it when it passed Earth again in 2014. ESA had to switch off the International Ultraviolet Explorer space telescope in 1996, for lack of funds to operate it, although it was still in full working order, and to this day there’s no full substitute for it. A similar controversy now surrounds the Chandra x-ray space telescope, launched in 1999 as one of the four ‘Great Observatories’ including the Hubble Space Telescope, and the last still to be operating along with the HST. It too is working perfectly well, but the cost of processing the data is rising steadily, and NASA has not been allowed funds to continue it beyond the current financial year.

 

ESA orchestrated the final descent of the Rosetta probe on to the surface of Comet 67-P in 2016, with the help of artist Carlo Palazzari, who had produced animations of the mission throughout. I said at the time that it ‘would bring a teat to a gless e’e’; but when Cassini made its fatal plunge into the atmosphere of Saturn the following year, NASA just prosaically recorded ‘Loss of Signal’. Before losing Ingenuity’s signal, the Jet Propulsion Laboratory pre-recorded an emotional farewell message to the controlling team.

 

Although Ingenuity is now out of contact, its fate is different again. Because its signal is too weak to reach Earth, NASA has left it on, and it has enough memory to store weather and other data for the next 20 years, and it will wake up for a while, each Martian day, to do so. Whether anyone will get to Mars in time to collect the data remains to be seen. At least it won’t be left sadly transmitting in hopes of a reply, as a cartoonist imagined for the Spirit rover when it got stuck in sand and couldn’t maintain solar power through the winter.

 

Perseverance has turned aside from the ancient riverbed piercing Jezero crater, to examine a rock on the inner rim called ‘Bunsen Peak’ (after a feature in Yellowstone National Park). Perseverance has taken two samples from it, by drilling and abrasion; analysis of the latter shows it to be composed almost entirely of carbonate material, bound by nearly pure silica, and it’s thought to have formed on the shore of the lake which once filled Jezero, and to be particularly likely to contain evidence of life. After examining an equally intriguing rock named ‘Bright Angel’, before taking a month to scale the crater rim looking for more ancient material thrown up from the depths by the impact. The drill sample, named ‘Comet Geyser’, is the 24th to be deposited by Perseverance for future collection. Unfortunately the cost and timescale of the retrieval ($11 billion, for return to Earth by 2040) have both been judged unsatisfactory, and the whole Mars Sample Return is now under review.

 

Jupiter, Uranus and Neptune will all be too low and too close to the Sun to see from here. Uranus is at conjunction on the far side of the Sun on May 13th, and Jupiter is at conjunction on the 18th.

 

Jupiter’s volcanic moon Io continues to unveil dramatic images and results from its close flybys, within 930 miles, by the Juno spacecraft in December 2023 and February 2024. An image from February 3rd shows the sub-Jovian hemisphere for the first time since the Voyager 1 flyby of March 1979. An image from the previous day shows the 200-km long Loki Patera, first imaged by Voyager 1 and later by Galileo in 1997, and the Juno image provides further evidence that it’s a lake of molten sulphur, fed by lava flows around its edge and with floating islands of sulphur on its surface. A feature named ‘Steeple Mountain’, 5-7 km high with sheer sides, is also attracting attention. Juno performed a more distant pass of Io at 10,250 miles on April 4th, and will complete its 61st orbit of Jupiter on May 12th. (Nancy Atkinson, ‘Juno Reveals a Giant Lava Lake on Io’, Universe Today, online, April 20th 2024.)

 

Studies of the isotopic composition of Io’s sulphur have found that it’s more dense than average, due to differentiation in which lighter isotopes have diffused into space from the atmosphere after ejection from the moon’s volcanic plumes. The ratio suggests that Io has been volcanically active, in constant eruption driven by tidal interaction with Jupiter, since its formation 4.6 billion years ago. That too is remarkable because studies of exoplanets such as K2-18b have concluded that their entire surface may be molten due to heating from the same cause. The cosmonaut artist Andrei Sokolov produced a set of paintings showing human explorers showing such a planet which had evidently solidified, yet was still bright red, perhaps because it orbited a red dwarf star or a red giant which had passed the peak of its expansion. The continuing presence of an atmosphere might suggest the latter, since it looks as if tidal action which keep most of Io molten for a long time to come.

 

Saturn, in Aquarius, is close to the waning Moon on the 4th, when it’s occulted by it as seen from Australia and New Zealand, but it’s not likely to be seen from Scotland till the end of May, as above, when it will be near the Moon and rise about 3 a.m. (BST). As Saturn approaches its equinox the rings grow narrower, seen from Earth, and are now at an angle of only 2 degrees to us.

 

Pluto is in the news thanks to a new study at the University of Bern, of the western lobe of the heart-shaped feature named Sputnik Planitia. The feature is bright because it’s a depression full of nitrogen ice, within which water icebergs travel along the cracks – suggesting hitherto that there may be liquid water below, perhaps still liquid from the impact which formed the basin, possibly implying a water ocean surrounding the planet’s core. But Pluto and its relatively large satellite Charon have mutually trapped rotations, and Sputnik Planitia is direct opposite the sub-Charon point, which should mean that its contents are more dense than their surroundings, rather than more. The new suggestion is that the bottom of the basin is a ‘mascon’, like those filled with dense lava on the Moon, but this one is the core of a rock impactor, 400 km in diameter, deposited in an oblique low-velocity impact. Its nitrogen filling comes from ammonia released from the crust by the impact, and no sub-surface oceans in required – or if there is one, to explain the icebergs, it must be very shallow.

 

There’s good news from Voyager 1, which has been out of touch in interstellar space for over five months. The problem is made worse because at its great distance (currently 24 billion km), an exchange of signals with the spacecraft takes 45 hours. However, by repeatedly ‘poking’ it with commands, engineers succeeded in getting a full engineering download from the spacecraft and identifying the problem, which lies with a single chip in the Flight Data System, at the point where signals are packaged for transmission to Earth. Whether it has suffered a cosmic ray strike or simply died of old age is uncertain. Engineering data has been redirected to bypass the chip, and the ground team are now in touch with Voyager in real time, as nearly as the time-lag will allow. The spacecraft has proved to be in good shape in all other respects, except that the backup for the FDS stopped working after the Saturn flyby in 1980, so outgoing transmissions can’t simply be switched to it, and there isn’t enough memory in the onboard computer to repackage the science data the same way. But six or more years of data before Voyager’s power finally gives out are worth fighting for, and the search for other solutions is on. As I’ve previously pointed out, the scientific instruments are being switched off one by one to conserve power as the end drawn nearer, and there may be some hard decisions ahead, as to which ones to switch off early to provide more memory for the rest.

 

One intriguing feature of the success so far is the photograph of the Voyager team celebrating their success to date on April 20th. When I visited the Jet Propulsion Laboratory in Pasadena in 1986, my friend Mike Urban was in charge of one of the two teams controlling Voyager 2, after its Uranus flyby that year, and there were only three people on each shift. Presumably more were called back for the demanding task of programming the spacecraft for its Neptune encounter in 1989. But as I remarked last month, Voyager 1 has been in cruise mode since 1980, apart from its last photo assignment in 1990 when it imaged all the planets including Earth as the ‘pale blue dot’. Looking at the people on the far side of the table in the celebration picture, I suspect many of the ‘science and engineering teams’ quoted (Carolyn Collins Petersen, ‘NASA Restores Communications with Voyager 1’, Universe Today, April 22nd 2024), are volunteers, possibly called back from retirement. But whether or not that’s true, the best of luck to them all.

 

The eta Aquarid meteors, one of the two showers from Halley’s Comet, will peak on the night of May 6th, and although the shower will not be a strong one, with the comet just past its furthest distance from the Sun, there will be no Moon to mask the meteors that do appear.

 

The Event Horizon Telescope (an international link-up that effectively generates a telescope the size of the Earth) has obtained a new image of Sagittarius A*, the black hole at the centre of the Milky Way galaxy. The first black hole to be imaged in that way, in 2019, was the supermassive one in the galaxy M87, followed four years later by a polarised image showing the structure of magnetic fields around it. Sagittarius A* was first imaged in 2022, and although it’s much smaller than M87’s black hole (4.1 million times the mass of the Sun, as opposed to 6 billion times), the latest image shows that the polarisation is remarkably similar. Sagittarius A* is so much smaller and closer to us that the pattern changes almost daily; what remains to be learned is whether all massive black holes have this pattern, or whether we happen to have captured ours when it momentarily looks like M87’s (‘News Update: Milky Way’s Black Hole Has a Magnetic Surprise’, Astronomy Now, May 2024).

 

Duncan Lunan’s recent books are available through Amazon. For more information see Duncan’s website, www.duncanlunan.com.

 

 

 

The Sky Above You

 

By Duncan Lunan

 

About this Column

 

I began writing this column in early 1983 at the suggestion of the late Chris Boyce.   At that time the Post Office would allow 1000 free mailings to start a new business, just under the number of small press newspapers in the UK at the time.   I printed a flyer with the help of John Braithwaite  (of Braithwaite Telescopes)  offering a three-part column for £5, with the sky this month, a series of articles for beginners, and a monthly news feature.   The column ran from May 1983 to May 1993 in various newspapers and magazines, but never in more than five outlets at a time, although every one of those 1000-plus papers would have included an astrology column.   Since then it’s appeared sporadically in a range of publications including The Southsider in Glasgow and the Dalyan Courier in Turkey, but most often, normally three times per year, in Jeff Hawke’s Cosmos from the first issue in March 2003 until the last in January 2018, with a last piece in “Jeff Hawke, The Epilogue” (Jeff Hawke Club, 2020). It continues to appear monthly in Troon's Going Out and Orkney News, with an expanded version broadcast monthly on Arransound Radio since August 2023

 

 The monthly maps for the column were drawn for me by Jim Barker, based on similar, uncredited ones in Dr. Leon Hausman’s “Astronomy Handbook”  (Fawcett Publications, 1956).   Jim had to redraw or elongate several of them because they were drawn for mid-US latitudes, about 40 degrees North, making them usable over most of the northern hemisphere.   The biggest change needed was in November when only Dubhe, Merak and Megrez of the Big Dipper, as the US version called it, were visible at that latitude.   In the UK, all the stars of the Plough are circumpolar, always above the horizon.   We decided to keep an insert in the January map showing the position of M42, the Great Nebula in the Sword of Orion, and for that reason, to stick with the set time of 9 p.m., (10 p.m. BST in summer), although in Scotland the sky isn’t dark then during June and July. 

 

To use the maps in theory you should hold them overhead, aligning the North edge to true north, marked by Polaris and indicated by Dubhe and Merak, the Pointers.   It’s more practical to hold the map in front of you when looking south and then rotate it as you face east, south and west.   Some readers are confused because east is on the left, opposite to terrestrial maps, but that’s because they’re the other way up.   When you’re facing south and looking at the sky, east is on your left.  

 

The star patterns are the same for each month of each year, and only the positions of the planets change.   (“Astronomy Handbook” accidentally shows Saturn in Virgo during May, showing that the maps weren’t originally drawn for the Hausman book.)   Consequently regular readers for a year will by then have built up a complete set of twelve.

 

 

©DuncanLunan2013, updated monthly since then.

 

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