The Sky Above You, September 2025
by Duncan Lunan
The Moon is Full on September 7th, and it will be New on September 21st, the day before the autumnal equinox. On the 7th there is a lunar eclipse which will be seen in full from Australia, Asia and Africa, but whose total phase ends as it rises in the UK at 7.53 p.m., with the partial phase ending at 8.56 p.m.. It's followed by a partial solar eclipse on the 21st, visible only from the south Pacific and Antarctica. The Moon passes Saturn and Neptune on the 8th, crosses the Pleiades on the 12th, is near Jupiter, Castor and Pollux on the 16th and 17th, and lastly occults Venus on the 19th.
Currently the largest and most powerful solar telescope in the world is the 4-metre one at the Daniel K. Inouye National Solar Observatory, Haleakalā, 'the house of the sun', on Maui in Hawaii. Commencing operation in 2010, it has ten times the resolving power of any similar observatory, and shows granulation on the solar surface at the scale of Manhattan Island). It has been looking at large features like sunspots in unprecedented detail, and other features down to 18 km in size, never seen before. On 27th August 2025 an image was released showing magnetic loop strands in the corona, the Sun's upper atmosphere, 29.95 miles (48.2 km) wide on average, some as thin as 13 miles (21 km), above a bright solar flare and the sunspot into which the loops are streaming. I don't usually give references in this broadcast version of the column, but on publication day of 'The Sky Above You, September 2025', ON, 2nd September 2025, the Daniel K. Inouye Solar Observatory published more images and information about the story. They appeared in the September 2nd issue of EarthSky, online, headed 'Two disasters [Afghanistan and Sudan], Sharpest Ever Solar Flare Image'.
And barring a total revolt in Congress within weeks, it is to be shut down as part of massive cuts in the budget of the National Science Foundation, along with NASA's, eliminating almost everything that doesn't serve big business or contribute to putting Americans back on the Moon within the Trump Presidency. As Congress is dominated by Republicans that revolt is unlikely, although some Congressmen can be expected to speak against the huge job losses in their respective states. But for the next couple of months, most items of astronomy and space news can be expected to end like this.
The planet Mercury is not visible this month.
Venus in Cancer rises at 4 a.m., and was one degree from the cluster Praesepe, the Beehive, on the morning of September 1st. On the 9th it moves on into Leo, passing Regulus, the brightest star there, on the morning of the 19th, when it's occulted by the waning crescent Moon, in daylight, disappearing at 11.34 a.m. and reappearing at 3.26 p.m.. The Collins 2025 Guide to the Night Sky says only that it will be visible from London, but according to another online search, it can be seen from Orkney, Shetland and Northern Ireland.
Mars has now disappeared behind the Sun, till next year.
Continuing study of the samples from the asteroid Bennu, returned by the OSIRIS-REx spacecraft in 2023, have confirmed that its crust contains material from interstellar space pre-dating the origin of the Solar System, and materials formed at different distances from the early Sun, which continue to tell us more about it and about the dust and gas from which it and the planets formed. In particular, the water bound up in the different types of rock may resolve the question about where the Earth's water came from - within the planet, or by bombardment? - and the naturally formed organic compounds will tell us more about the precursors to life here. (Elizabeth Howell, ''Potentially hazardous" asteroid Bennu contains dust older than the solar system itself — and traces of interstellar space', MSN News, online, 26th August 2025.) It appears that the parent body which formed from these materials, and then shattered in subsequent collisions, formed in the same part of the early Solar System as the asteroid Ryugu, from which Japan's Hayabusa-2 returned samples in 2020. They may even have had the same parent body, of which the Polana asteroid group in the Main Belt are the surviving fragments, with Polana itself much the largest at 55 km across. Both Bennu and Ryugu have been pushed nearer the Sun by Jupiter, and their surfaces have evolved differently in consequence. (Evan Gough, 'It's Official: Asteroids Ryugu and Bennu Are Siblings', Universe Today, online, 19th August 2025.)
As part of periodic testing and calibration of the Psyche spacecraft's science instruments during its cruise phase towards the metallic asteroid of the same name, the spacecraft has taken long-distance images of Mars and Jupiter, and of the Earth and Moon from 180 million miles, on July 20th and 23rd among background stars in the constellation Aries. Further targets may include Saturn and the asteroid Vesta, which was orbited by the Dawn probe in 2011 – long before these columns began, but I discussed the findings in Incoming Asteroid! What Could We Do About It?, (Springer 2013).
The same book discussed the proposal by Prof. Colin McInnes of Glasgow University, to deflect threatening asteroids by launching impactors, to forcibly change their trajectory. The experiment has since been tried with the DART probe which struck Dimorphos, the satellite of the asteroid Didymos, in September 2022. A significant change was made to Dimorphos's orbit, but images from the accompanying LICIAcube microprobes have struck a cautionary note. The debris streams from the impact were much larger and more compact than expected, and Dimorphos may have been resurfaced by material swept up again; Europe's HERA probe is on the way to study the effects on the two bodies after the impact. Two stream of boulders were ejected, 104 objects in all, and it appears that they came from fragmentation of larger boulders on the asteroid's surface by the probe's solar panels in the fraction of a second before the main impact (Deborah Byrd, 'NASA’s DART mission unleashed a blitz of boulders into space', EarthSky, July 9th 2025). I've seen it suggested that one of those new meteor streams will hit Mars, and another of dust (at least) will cross the Earth's path later; however the original paper says that the orbital changes are small, though the debris conceivably could evolve into Earth or Mars-crossing objects in time (Tony L. Farnham, Jessica M. Sunshine et al, 'High-speed Boulders and the Debris Field in DART Ejecta', The Planetary Science Journal, July 4th, 2025). As Jay Tate of Spaceguard UK said in the Incoming Asteroid! discussions, 'You have to be very sure that you won't turn a cannon-ball into a shotgun blast'.
OSIRIS-REx, now renamed OSIRIS-Apophis, is now heading to the asteroid Apophis, which will make a very close pass of the Earth in 2029, coming close to the 'comsat ring' of geosynchronous orbit, with another in 2036, both so close that a minor change in its path could lead to a catastrophic impact. Apophis, named after the Stargate villain (named after a minor Egyptian deity) was discovered in 2004, and we were often asked in the Incoming Asteroid! project why we didn’t focus on Apophis when it had been used as the basis for many other studies. One reason was that our project had been running for two years before Apophis was discovered, and we had already settled on a 'designer hazard' which we called 'Goldilocks' - neither too hard to intercept nor too easy, not too big nor too small to be a major hazard, and with neither composition nor rotation making it too difficult to deal with, though still far from easy. Apophis by contrast was comparatively easy to get too, comparatively small (about 350 metres), but with composition unknown. Thanks to Robert McNaught from Prestwick, now at Siding Springs in Australia, it turned out that Apophis would not hit the Earth in 2029 or 2036, and there was only one chance in 300,000 of doing so in 2068. ESA is scrambling to get a flyby probe to Apophis as it goes past in 2029, and OSIRIS-Apophis was going to catch up with it immediately afterwards and go into orbit round it for detailed study. Having no interest in that either, and with it lying outside the current Presidency in any case, the White House has ordered OSIRIS-Apophis to be switched off next month.
Jupiter in Gemini now rises around 00.30 a.m., passing Castor, Pollux and the Moon as above.
After a communications glitch on August 16th, caused by a mis-set timer, ESA's JUpiter ICy Moons Explorer (JUICE) is fully operational and was ready for a Venus flyby on August 31st which put it on its outbound course to reach Jupiter in 2031, after two more Earth flybys. The Venus flyby took no photographs because the sunlight was too intense for the cameras, which are designed to function at the much lower light level of the Jupiter system, though they worked fine in the first Earth flyby of August 19th 2024. Passing Venus, the heat from the Sun and the heat reflected from the Venus clouds on the other side would together have been too much, and the spacecraft's high-gain parabolic antenna was pointed towards Venus at closest approach, to reflect as much heat as possible back towards the planet. Venus and Jupiter are still fairly close in the sky after their conjunction in August, and a dramatic photograph during the flyby shows them in line with the antenna of ESA's Deep Space Antenna 2 at Cerebros, 77 km west of Madrid. As well as tracking their own spacecraft, ESA's network often contributes to the missions of other nations, including NASA's Deep Space Network and China's lunar missions. The next two Earth flybys will be in September 2026 and January 2029, finally beginning the outward coast to Jupiter in 2031.
After 35 passes over the Galilean moons during 2.5 years, JUICE will go into orbit round Ganymede, the largest moon in the Solar System, which will be the first orbit of any moon other than our own.
NASA's Europa Clipper mission has escaped the Trump Presidential axe, at least for now, and is continuing on its outbound path to arrive in 2030. During a Mars flyby on March 1st, Europa Clipper took the opportunity to test its terrain-mapping REASON radar system (Radar for Europa Assessment and Sounding: Ocean to Near-surface and obtained a plot of its surface track, which doesn't look very exciting, but holds great promise for the spacecraft's 50 scheduled orbits of Ganymede.
Saturn in Pisces is visible all night, passed by the Moon on the 8th, at its nearest to us and brightest for the year when it reaches opposition on September 21st, when it will be due south at midnight GMT, 1 a.m. BST.
Uranus rises at 9.30 p.m., between the Pleiades and Hyades clusters in Taurus. In 2025 it was announced that the James Webb Space Telescope had discovered a 29th moon of Uranus, 6 km in diameter and just outside the ring system, which is face-on to JWST at the Sun Earth L2 point. Because Uranus and its rings orbit the Sun on their side, and the Uranus year is 84 Earth years, if the JWST lasts 10 years as planned the rings will change inclination by 42 degrees approx.. All the moons of Uranus are named after characters in Shakespeare, except for Umbriel who's a character from Pope's The Rape of the Lock, and although some photo captions are confusing, this one is not to be confused with 'Cordelia', after the unfortunate youngest daughter of King Lear, which was discovered by Voyager 2 in 1986, a 'ring shepherd' just inside the outermost ring, 34-46 km across, not visible in the JWST image due to the glare from the rings themselves. The Uranus rings are extremely dark, so show up brightly in infrared due to the sunlight they absorb as well as what they reflect. For more details see 'New Moon for Uranus', EarthSky News, online, 21st August 2025.
Neptune in Pisces is at opposition on the 23rd, in the sky all night like Saturn, nearby, and the Moon is between them on the 8th.
There's an increasingly mysterious object called 3I/ATLAS coming our way, about which I've written articles for Orkney News called 'Interstellar Comet' and 'Little Red Dots, Interstellar Comet' (10th and 24th August 2025). I misprinted it several times as '31/Atlas' (I'm obliged to my friend Del Cotter for pointing that out), as if it was the 31st object discovered by ATLAS (Asteroid Terrestrial-Impact interstellar Alert System), which has two telescopes on Hawaii and one each in Chile and South Africa – an understandable confusion, perhaps, when asteroid 2024 YR4, also discovered by ATLAS, is still in the news, with the possibility of a lunar impact in 2032. In the correct designation, 3I/ATLAS, the 'I' stands for 'Interstellar' because this is only the third such object to be discovered on approach.
In that article I speculated that the notion that it was artificial might have substance if its origin was close to the Galactic Centre, as 1I 'Oumuamua's was to the Apex of the Sun's Way. The full track has now been published, from pre-discovery images in mid-May, through discovery on 1st July, to likely disappearance beyond Jupiter in March 2026. The backward trail has now been extended to May 7th with data from NASA's Transiting Exoplanet Survey Satellite (TESS). In the chart the asterism of 'The Teapot' in Sagittarius is visible at lower left, below the trail of 3I/ATLAS, so demonstrably it didn't come from there.
Some articles that I've seen state that 3I/ATLAS was already displaying a cometary halo and tail in early May, but that is not true, although there was other activity. (Avi Loeb, 'Detection of an Anti-Solar Tail for 3I/ATLAS', Medium, online, 30th August 2025). Shortly after discovery, on July 5th and 21st attempts were made to obtain spectral data using the Gemini South and NASA IRTF telescopes, and announced as unequivocally demonstrating the presence around the comet of water vapour and other gases typically found in cometary halos. Avi Loeb strongly disagreed with that finding ('No, There’s No Clear Evidence for Water Around 3I/ATLAS', Medium, August 8th, 2025), and has proved to be right in further studies by the JWST on August 6th, the Hubble Space Telescope on August 7th, and SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer), August 7th to 15th. Throughout, no coma or tail developed and all that could be seen was a cloud forward of the object, at first composed of dust but later including carbon dioxide and monoxide, while the only evidence of water was in reflection from the object's surface, apparently mixed with carbon dioxide. Nevertheless we appear to be seeing the same intellectual process that we saw with 'Oumuamua, where first it had to be an asteroid, then when it didn't look like one it had to be a comet, though it didn't look or behave like one, more like a sheet of polished metal. Now there seems to be general agreement that come what may, 3I/ATLAS is a comet and that's what even I have been calling it until proved wrong. At last it's developing a faint tail of carbon dioxide gas ('Detection of an Anti-Solar Tail for 3I/ATLAS', above), but that's very different from the water, cyanogen etc found in comet halos, and the ion tails and dust tails which grow out of them.
One of the weird aspects is that 3I/ATLAS's forward dust cloud is showing increasing evidence of nickel. Nickel-iron is formed by internal differentiation of rocky bodies due to internal radioactive heating, so it makes up most of the core of the Earth, the other terrestrial planets and most of the meteorites which survive atmosphere entry to reach the Earth's surface. The largest source of nickel on that surface is the Sudbury impact feature in Canada. But as Avi Loeb points out, to get nickel on its own you normally have to refine it from iron ore by industrial processes, to which one well-known astronomer has replied, "This is nonsense on stilts". I won't mention who said that because I'm reminded of a BBC interview with myself, the late A.T. Lawton and Sir Bernard Lovell in January 1973, after which the producer told us, "We'll edit that to spare Sir Bernard embarrassment in case you're proved right". For now, we can only wonder what 3I/ATLAS has up its sleeve to surprise us with next.
On the subject of possible extraterrestrial communications, a very interesting idea has come up about the 'WOW signal', detected in August 1977, by the Big Ear radio observatory of Ohio State University. Its intensity, narrow bandwidth and brevity all suggested it might be artificial, and first thoughts were that it probably came from some nearby source, like the recent mysterious burst from the defunct Relay 2 comsat (see 'Space Notes, July 2025', ON, July 1st 2025). New analysis by the Arecibo Wow! project at the University of Puerto Rico at Arecibo has pinpointed the source with greater accuracy and terrestrial interference, including aircraft and satellites, now appears to be ruled out (Paul Scott Anderson, 'The Wow! Signal: New analysis closes in on mysterious source', EarthSky, August 24th 2025.)
On the other hand, searches for an extraterrestrial source have also drawn a blank. The signal never repeated, and no promising stars have been found that could host habitable planets, even in the much more detailed catalogues now available from the mapping of the Galaxy by the GAIA space telescope (see 'The Sky Above You, February 2025', ON, February 1st, 2025). A very detailed search by Jodrell Bank failed to find any 'traffic' from other civilisations anywhere around the line of sight, right across the Galaxy. And now there is a possible explanation which does not require such a civilisation to be there.
The WOW! signal was on 'the hydrogen line', the 21-centimetre radio emission of neutral hydrogen, which is thought to be the prime wavelength for interstellar communication just because any civilisation with radio astronomy is bound to be aware of it. Clouds of the material are everywhere, and the new suggestion is that one such cloud was briefly lit up by a Fast Radio Burst from a magnetar, a very active form of pulsar surrounded by extremely powerful and complex magnetic fields. A still more powerful burst from a source far away in the Universe would probably have been detected here too, but one from a recently formed pulsar within the Milky Way would be sufficiently directional to light up the cloud as a natural maser, emitting a coherent signal which we detected here, though the beam which triggered it didn't come our way (and so much the better for us, if its source was anywhere in this quadrant of the Galaxy). It could explain everything, including the non-repetition of the signal and the lack of any detectable source for it. It has a ring of truth, even if it's disappointing for the Search for Extraterrestrial Intelligence.
Another mystery, definitely natural but possibly scary for us, has come a step nearer resolution. Among its many discoveries, the Fermi gamma-ray observatory, launched in 2008, detected huge 'bubbles' extending 50,000 light-years above and below the centre of the Galaxy. The intensity of their gamma-ray emission suggested that they might be composed of antimatter, perhaps emitted from a white hole 'gusher' leading from another part of the Universe, or from another universe altogether. Signals from a distant quasar passing through one of them revealed that it was still expanding at 2 million miles per hour, giving it an age of 2 million years. Other possible explanations included a collision with a dwarf galaxy and collision of its central black hole with our own, though there haven't been any as recent as that. Whatever the event was, it was so violent that cold gas clouds, like the one possibly responsible for the WOW! signal, were ejected bodily from the Galaxy's central bulge without having time to heat up. Similar ones have been identified in similar bubbles from the centre of the radio galaxy Centaurus A, and they confirm a maximum age of a few million years for the events.
On the face of it, that's good news for us. Whatever the event was, it doesn't seem to have done serious damage to the Earth. Between 10 million and 1 million years ago, there are glitches in evolution caused by supernovae, volcanic eruptions, glaciations etc, but nothing to indicate a catastrophic event on a galactic scale, like the one portrayed by Fred and Geoffrey Hoyle in The Inferno (1973). Then again, in the novel we are saved at the last gasp by a higher civilisation which puts a temporary shield between Earth and the terrible thing blazing in Sagittarius. Maybe the Fermi bubbles are telling us that we're still here because we're not alone, after all.
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.