The Sky Above You, May 2025
by Duncan Lunan
The Moon is Full on May 12th, shortly after apogee (furthest from the Earth) the previous night, and it will be New on May 27th, the night after perigee. It passes Mars and the cluster Praesepe in Cancer on May 3rd and 4th, passes Venus and Saturn on the 22nd to 24th, and is above Jupiter on the 28th.
The planet Mercury is not visible this month, too near the Sun, and is at perihelion (physically nearest the Sun) on the 31st, a day after superior conjunction.
Venus is low in the morning sky, at its greatest elongation from the Sun on the 31st (Astronomy Now says June 1st). Venus is passed by the Moon on the 24th, with Saturn the other side of the Moon (right) from the 22nd to the 24th. Their 'smiley face' conjunction on April 25th was predictably nothing like as dramatic as it was supposed to be, but actually turned out quite well in photographs.
After the first successful landing by Venera 7 in 1970, the Soviet Union's Venus entry probes were redesigned for a new series designated Veneras 8-12. The first two of these were launched in 1972 and Venera 8, launched in April, landed successfully in July. Its sister ship suffered a failure of the upper stage during transfer orbit insertion on March 31st and came apart into four pieces, two of which fell in New Zealand and the other two, presumed to be the engine unit and payload, remained in elliptical orbit between 210 and 9800 kilometres up. One of the others, Kosmos 482, is expected to fall somewhere between latitudes 52 degrees north and south, between May 9th and 11th this year. ('Kosmos' was a catch-all designation for Soviet Earth orbiters, successful or otherwise.) If it's the payload, dire predictions are being made that the entry capsule could impact with the force of a meteorite. It is equipped with a parachute, but that's not likely to deploy after all these years. Either way, first it has to separate from the interplanetary carrier, otherwise it will tumble and slow down; and since the 'chute was to have deployed at Earth-atmosphere pressure levels, the solo capsule will decelerate to subsonic speed before reaching Earth's surface. At worst it will be like the crash of Soyuz 1, whose parachute failed to open, and although that landed hard and killed the cosmonaut, catching fire afterwards, it was nothing like a meteorite - and the Venera capsule is a lot smaller.
Mars is now in Cancer, between Regulus in Leo and Castor and Pollux in Gemini. Mars will be very close to the Praesepe cluster in Cancer on the 4th, but the nearby Moon will spoil the spectacle. Mars sets at about 2.00 a.m., and is to the left of the crescent Moon again on May 31st. Over the planet, the Mars Reconnaissance Orbiter has obtained an image of the Curiosity rover with 1,050 feet of its track descending from the Gediz Vallis stream channel to "a region with potential boxwork formations, possibly made by groundwater billions of years ago". The tracks "represent roughly 11 drives starting on Feb. 2 at a top speed of 0.1 mph (0.16 kph)", and the image is said to be the first of its kind, previous ones having been taken when Curiosity was stationary. That may be true, but MRO has repeatedly photographed rovers on the surface, first Opportunity and Spirit, then Curiosity and Perseverance, and whether moving or not doesn't make much difference.
At the Ubajara drill site on Mount Sharp in Gale crater, onboard analysis of four samples has produced a major discovery. All of them contained siderites, a mineral rich in carbonates, which may have sequestered carbon dioxide, and if widespread, might account for the disappearance of Mars's early atmosphere (Paul Scott Anderson, 'New discovery of carbonates on Mars could solve big mystery', EarthSky, online, April 24th, 2025.) On the assumption that such materials were widespread on Mars, in 1991 my friend Martyn Fogg evaluated the possibility of liberating the carbon dioxide to regenerate a dense atmosphere whose greenhouse effect could warm up the planet towards habitability. One such idea was pinpoint bombardment of such deposits, which were thought to be very thick on the floor of Valles Marineris, the Great Rift Valley, for example. (M. J. Fogg, 'The Once and Future Mars', Analog, January 2001.) The artist David A. Hardy produced a painting of the process which became an Analog cover in May 2001. Unfortunately even the Valles Marineris deposits are not large enough to produce a 1-bar atmosphere for terraforming, and even if siderites are common in the northern hemisphere of Mars, which may all have been ocean at one time, it would take thousands of full-comet-sized impacts to achieve the required effect. But the Marineris deposits could be a useful start to the process.
On the western rim of Jezero crater, at a steep layered slope called Witch Hazel Hill, the Perseverance rover has found a bonanza of rocks from deep within the planet, excavated by the impact which formed the crater. In the early mission, it could take months to move from one type of rock on the crater floor to another, and the attraction of the river flowing into the crater was that different rocks had washed down it from the terrain above. In ongoing study, rocks found in July and August 2024 contain 'leopard spots', black 'poppy seeds' and green spots which could be traces of ancient life. But on the crater rim, Perseverance has been finding much more diversity, including 'Silver Mountain', a much older rock, dating back 3.9 billion years to when the planets were newly formed and the Final Bombardment phase was still in progress. The finds include 'serpentine materials', which typically form when water interacts with some volcanic rocks, sometimes creating hydrogen, a potential energy source for life. In the past few months, Perseverance has collected samples of five rocks, performed detailed analysis on seven others, and 'zapped' an additional 83 with its laser for remote study. (Sharmila Kuthunur, 'NASA's Perseverance rover hits the Mars rock gold mine: "It has been all we had hoped for and more", Space.com, online, 16th April 2025).
On its way down from Witch Hazel Hill, Perseverance has found still another oddity, a pitted rock nicknamed 'Skull Hill', in an area called 'Port Anson', where there are a number of similarly dark-hued boulders which don't fit with the terrain. In geology such anomalies are called 'floaters', but this one is high above the riverbed in which Perseverance found other strange rocks apparently washed downstream. It may be igneous, though there are no volcanic vents on the crater rim, so it could have been ejected from another impact crater or a distant eruption, long ago.
After delivering samples from asteroid Ryugu in December 2020, Japan's Hyabusa 2 space probe is currently heading for the small but near-spherical asteroid 1998 KY26, to arrive in 2031. But on March 21st it experienced an 'anomaly'. As of April 17th it was still in 'safe mode' and in touch with Earth, but there's no further news.
On its way to the Trojan asteroids in the orbit of Jupiter, on April 20th the Lucy spacecraft flew by the Main Belt asteroid Donaldjohanson. The flyby was at 600 miles, so close that the only video hitherto released, as of April 29th, doesn't show the whole of it, though proving it to be a 'contact binary' of two objects, joined by a neck of material which has flowed to the common centre of mass between them. It will take at least a week for the full data to be released, so for 'Space Notes' (ON, 27th April), I compared that first image to other similarly paired objects in the same size range, as well as smaller and larger solo ones, and went on to explain with orbital diagrams why the surface composition may prove to be particularly important. More details will have to wait till later.
Jupiter is still bright in Taurus, but setting around 11.00 p.m. by the end of May, with the thin crescent Moon above it on the 28th, shortly before it disappears into the afterglow of sunset.
In the February 'Sky Above You', I highlighted the extraordinary discovery that astronomers have been wrong for decades, in identifying Jupiter's bright bands as high-level cirrus-like layers of ammonia ice crystals. Whatever they are, they're too low in the atmosphere for ammonia ice to form. I went on to add, 'When the Pioneer probes found towering white plumes with intense lightning activity in gaps in Jupiter's clouds, and Ed Buckley painted one in 1975 for my Man and the Planets (Ashgrove Press, 1983), they too were assumed to be ammonia ice. But in May 2020 they turned out to be water ice, all the way up into the supposed ammonia ice levels, and I wondered if that may be at least part of the answer on a much larger scale - perhaps with different types of ice, as SF writers going back to James Blish had suggested. Continuing study by the Hubble Space Telescope, the Very Large Array, and the Juno orbiter, have suggested that rising plumes of ammonia are interacting with the water ones to produce 'slushballs', in which the ammonia acts as antifreeze, so instead of hailstones, balls of mush are forming and growing to softball size before falling back into warmer layers. It now appears that this is happening on such a scale that it depletes the ammonia in whole bands of the middle atmosphere. Ammonia is depleted above 'hurricane-like vortices', which I take to be the 'white ovals', as large as the Earth and visible from here, which show hurricane-like patterns and are now suggested to have ammonia concentrations in their central layers. (Shireen Gonzaga, 'Ammonia-water mushballs raining on Jupiter, says new theory', EarthSky, online, April 23rd 2025).
Saturn in Pisces rises about 4.00 a.m., to lower right of Venus in early May, but will be hard to observe before the end of the month. Saturn's conjunction with the Sun on 18th March was observed by the SOHO spacecraft from the Sun-Earth L1 point, a million miles to sunward of us, and while it was invisible from Earth we passed through the plane of the rings, from our viewpoint, on March 23rd. On Saturn, the Sun's ring plane crossing occurs as it passes through its autumn equinox on May 6th. Interesting events have been seen at such times in the past, and although we can't see them from here, this time, we'll soon know whether any other spacecraft have seen any. But as Nigel Henbest says in Stargazing 2025, Saturn should now look markedly different when we're observing the rings from the other side, from below instead of above. The Moon will be near Saturn on the 22nd, as above, and between Venus and Saturn on the 23rd.
Uranus in Taurus and Neptune in Pisces are not visible this month. Uranus is in conjunction with the Sun on May 18th.
On the morning of 6th May the eta Aquarid meteors from Halleys's Comet will peak in a moonlit sky, but with the comet now at its furthest from the Sun, not much was expected anyway, nor for years to come.
For some better news, NASA's SphereX space telescope is now in orbit, and beginning a whole new set of all-sky surveys. With a heat shield shaped like a muffler for an angry dog, it's expected to cover 450 million galaxies, and 100 million stars in the Milky Way, even more than the recently deceased Gaia telescope.
Update: in mid-April it has been difficult over the nights of the Full Moon to observe the faint stars of Corona Borealis, below Boötes the Herdsman in the east, mid-evening, where an outburst of nova T Coronae Borealis is expected any time, after 80 years. I've bought a new pair of binoculars from the chandler's on Lamlash pier, to make sure I don't miss it when it happens. As I reported last month, though it isn't 'due' till 2026, the star has been flickering as it did before the last event. The circlet of Corona Borealis is below and to the left of the red giant star Arcturus, and its brightest star is Alphecca, 2nd magnitude like the stars of the Plough. If you see two stars there, one just off the circlet, then the nova is taking place.
But on a sad note, with regret I have to note the passing of the Troon-based astrophotographer Mark Ferrier, who died suddenly of a heart attack on April 20th. I first saw his work on display at the Little Shop with No Name, a cafe on West Portland Street in Troon, which included an outstanding image of star trails over the War Memorial on Troon Promenade. His favourite subjects were noctilucent clouds and aurora, which Gerry Cassidy and I featured in issue 4 of Space & Scotland magazine in 2017. In 2014 he had photographed and filmed the southerly minor standstill moonset at the Sighthill stone circle ('Sighthill Observations', Orkney News, April 10th 2022), the only minor standstill event which anyone managed to catch during the circle's years at its previous location. In sending condolences to his wife Polly, it's hardly necessary to add that Mark will be greatly missed.
Duncan Lunan’s recent books are available through Amazon; details are on 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.