Indholdsfortegnelse for September 2025 i BBC Sky at Night

Find it at www.skyatnightmagazine.com/bonus-content SEPTEMBER HIGHLIGHTS Interview with a Rubin astronomer Dani Leonard reveals plans to use the new Rubin Observatory to probe the Universe’s biggest mysteries. Your best images of the Universe Our extended gallery featuring the best astro images sent to us by BBC Sky at Night Magazine readers. Take on the Messier Catalogue marathon Download the complete Messier Catalogue to your phone or tablet. How many targets can you tick off the list? The Virtual Planetarium Pete Lawrence and Paul Abel guide us through the best sights to see in the night sky this month.…

JWST has spotted evidence of a planet lurking in a disc of debris orbiting nearby star TWA 7. The object, known as TWA 7b, could be a young, cold planet with a mass similar to that of Saturn – around 100 times more massive than Earth. Debris discs orbit both young and old stars and are filled with dust and rocky material. They often contain gaps, thought to be created by planets forming around these stars. However, such a planet has never been discovered before. “Our observations reveal a strong candidate for a planet shaping the structure of the TWA 7 debris disc, and its position is exactly where we expected to find a planet of this mass,” says Anne-Marie Lagrange, one of the scientists who discovered the potential new…

I had one answer, every time: Jocelyn Bell Burnell. Whenever Amaury Triaud, my PhD supervisor, asked for speaker suggestions for our weekly seminars, hers was the name I suggested. Again and again. He’d patiently remind me that it might be tough to get her in, seeing as she’s a living legend and all, but still I asked. Finally, in October 2021, the day came when he told me that Professor Dame Jocelyn Bell Burnell would be coming to Birmingham and doing a meet and greet. “But there’s a catch,” he said. “The only slot she can do is in February.” “This coming February?” “That’s right. If you want to attend the talk and meet Jocelyn, you will have to cancel your trip to Antarctica.” I’ll be honest, I briefly hesitated.…

Imagine an early human out on the savannah, stepping away from the evening fire, glancing up at the dark sky and being totally captivated by the tiny, twinkling sparks dotted everywhere. Eyes wide, head tilted, and just the sound of his or her own quiet breathing and the crackling of the fire. Since the dawn of homo sapiens around 300,000 years ago, every other view of our planet has changed – mountains have been eroded, sea levels have risen and fallen, volcanoes and earthquakes have reshaped the land, and swamps have been drained. The only view that has stayed more or less the same is the night sky (the patterns of stars will have changed only slightly over that time due to proper motion). It blows my mind every time…

Jupiter’s magnetic field is truly immense. It extends far beyond the planet itself and is the strongest in the Solar System aside from that of the Sun. This field scoops up and accelerates particles to blistering speeds approaching the speed of light, acting as a giant cosmic particle accelerator. These super-hot particles exist in doughnut-like radiation belts wrapping around Jupiter’s middle; they can damage electronics when they collide with spacecraft, and so missions such as Juno are carefully planned to keep their probes protected. To avoid the worst of the planet’s radiation, Juno orbits on a highly stretched orbit that skims Jupiter’s poles. This orbit dodges the densest parts of the radiation belts, spending as little time in them as possible, and loops through a thin, relatively radiation-free gap sitting…

DON’T MISS Total lunar eclipse as the Moon rises BEST TIME TO SEE: 7 September 2025, from moonrise around 19:45 BST (18:45 UT) Remember the total lunar eclipse back in March? Unfortunately, for many observers across the UK, the weather wasn’t good, but if you were lucky enough to see it, you’ll remember that totality occurred just a few minutes before the Moon set: we got to see the initial partial phase of the eclipse, a hint of totality… and then the Moon was gone. Well, the good news is that this month there’s another total lunar eclipse and, in a way, it’s something of a mirror of the March event. Whereas in March, totality was reached just as the Moon set, the total eclipse due on 7 September will…

Few constellations are as easy to recognise as the ‘W’ of Cassiopeia. From the UK, this distinctive circumpolar pattern is as familiar as the Plough. The ‘W’ is formed from five medium-brightness stars. Caph (Beta (β) Cassiopeiae) marks the western end, the right-hand edge of the ‘W’. The star gets its name from ‘al-Kaff al-Khadib’, meaning ‘the stained hand’, as the preIslamic Arabic depiction of the five stars formed an outstretched hand. The phrase was shortened and came to refer to just Beta Cassiopeiae. It’s a Delta Scuti variable star, ranging from mag. +2.25 to mag. +2.31, with a spectral class of F2 III, indicating it’s a yellow-white giant. Caph is 54.7 lightyears away. It has a mass nearly twice that of our own Sun and is 3.8 times larger…

1. Picos de Europa, Cantabrian Mountains Totality: 1 minute 43 seconds, 9˚ above western horizon Observe the eclipse from Pico de la Tabla, framed by the rugged peaks of Picos de Europa. Explore! will lead the tour group. www.explore.co.uk 2. A Coruña, Galicia Totality: 1 minute 15 seconds, 12˚ The Tower of Hercules, a Roman-era lighthouse on the northwest coast, is where to see the eclipse from Galicia’s second city. www.turismo.ga 3. Sigüenza, Guadalajara Totality: 1 minute 38 seconds, 7˚ AstroTrails sets up at Sigüenza Castle, overlooking cathedrals, cobbled squares and centuries-old charm in a city declared a Historic-Artistic site in 1965. www.astro-trails.com 4. Parque Natural Cañón del Río Lobos, Castile and León Totality: 1 minute, 42 seconds, 7.5˚ This spectacular 16-mile-long limestone gorge and plateau is one of Spain’s…

As described on page 46, there will be a total lunar eclipse on 7 September that somewhat mirrors the one that occurred last March. Whereas March’s eclipse took place as the Moon was setting, with totality being achieved just before moonset, this one takes place at moonrise, with totality ending around 15 minutes after the Moon pops up above the horizon (as seen from the centre of the UK). Both events could be reasonably described as frustrating, as neither gives a decent view of totality. Still, if skies are clear, this month’s event should provide a good look at the second partial phase after totality ends. There are many ways to photograph a lunar eclipse and, as you’d expect, some methods work better than others. Using a smartphone is perfectly…

VITAL STATS Price £1,199 Optics Quadruplet refractor Aperture 86mm Focal length 602mm, f/7 Focuser Dual-speed rack and pinion Extras Tube rings with finder clamp handle, Losmandytype dovetail, camera adaptors, two finder shoes, carry case Weight 5.8kg Supplier First Light Optics Email questions@firstlightoptics. com www.firstlightoptics.com Earlier this year, First Light Optics announced a new addition to its in-house brand of telescopes, the StellaMira range. The 86mm f/7 quadruplet refractor is the first four-element telescope in the collection, with two extra-low-dispersion (ED) elements and a built-in flattener which promises a perfectly flat field of view, from corner to corner. It provides 602mm of focal length, which is perfect for a wide variety of popular targets, and – despite the rapidly disappearing darkness of our spring skies – we were excited to make…

What makes Chile, specifically the Atacama Desert, a prime location for looking at the cosmos? Chile is the best place on Earth for doing astronomy in different wavelengths. We have very clear and quiet skies, which are perfect for observations in the optical and infrared. We also have high, dry places in the mountains which are good for ‘millimeter’ and ‘submillimeter’ astronomy. Observing sites like the European Southern Observatory (ESO) Paranal site are in the middle of the Atacama Desert, far from big cities and their associated light pollution. What exactly is light pollution? It’s the brightening of the sky caused by the excess light that we human beings emit into the atmosphere. We emit a large amount of unnecessary light – say, from poorly positioned streetlamps and the blue…

VICTOR M BLANCO 4-METER TELESCOPE, 9 JULY 2025 This is NGC 6188, an emission nebula 4,000 lightyears from Earth, known as the Fighting Dragons of Ara because of its resemblance to two dragons preparing to face off (seen here in close-up). The nebula lies in the constellation of Ara, the Altar, and its reddish glow comes from ionised hydrogen that’s being illuminated by energetic outflows from the region’s many young stars, no more than a few million years old. The intense stellar wind blasting outwards from these stars has sculpted and shaped the surrounding gas and dust into the striking draconic forms we see today. Cluster buster JAMES WEBB SPACE TELESCOPE, CHANDRA X-RAY OBSERVATORY, 30 JUNE 2025 A new study of the Bullet Cluster is helping to shed light on…

About 16 per cent of all the Universe’s matter is ‘ordinary’, including everything from atomic nuclei to human beings. Unlike its mysterious counterpart, dark matter, it also emits light and interacts with other matter, meaning that it can – in principle – be detected. Despite this, a significant fraction of ordinary matter has gone unaccounted for, lost in the vast spaces between galaxies. Astronomers have now found it. The researchers from Caltech and Harvard’s Centre for Astrophysics used fast radio bursts (FRBs) – bright and fleeting flashes of radio-frequency radiation from the distant cosmos – to illuminate the sparsely spread missing matter. “The FRBs shine through the fog of the intergalactic medium, and by precisely measuring how the light slows down, we can weigh that fog, even when it’s too…

It’s human to feel alarmed by the sheer emptiness of space. Now, astronomers from the University of Portsmouth suggest this unsettling vastness may be worse than we thought, claiming that our entire Milky Way sits inside a mysterious giant hole. This void, they believe, may cause the cosmos to expand more quickly in our local environment than in other parts of the Universe. The void idea was proposed as a way of solving what’s known as the Hubble tension (or the Hubble crisis), a conundrum that has puzzled astronomers for years. The tension refers to the fact that the rate of the expansion of the Universe varies depending on where it’s measured. This discrepancy is a major problem for cosmologists, who need to know the expansion rate to accurately determine…

One of the Cassini orbiter’s stand-out discoveries in the Saturn system was plumes of water-ice erupting from fissures in the moon Enceladus. These ice particles make up the diffuse E ring surrounding Saturn. Now, a team fronted by Niels Rubbrecht, at the Delft University of Technology in the Netherlands, has found something just as unique created by Enceladus’s icy eruptions. Rubbrecht and his colleagues were looking through old photos captured by Cassini during its 17th close fly-by of Enceladus on 27 March 2012. They spotted distinct stripe-like features appearing around the moon in images taken by both the Visual and Infrared Mapping Spectrometer (VIMS) and the visible Narrow-Angle Camera (NAC) on the probe. The team went back through other Cassini images taken under similar lighting conditions, including fly-bys of other…

Driving up dusty mountain roads flanked by cacti and colourful bursts of wildflowers, it’s hard to imagine these quiet peaks in the Chilean Andes are home to some of the most sophisticated astronomical instruments on Earth. Atop Cerro Pachón, 2,715 metres (8,900ft) above sea level, the newly constructed Vera C Rubin Observatory is ready to reshape our understanding of the cosmos. Its 10-year Legacy Survey of Space and Time (LSST) is slated to start later this year. Visiting the facility in May, it was a marvel to see the telescope whirring to life. Gathered on a platform inside the dome with scientists and other visitors, I watched as the massive teal-coloured structure rotated and angled towards the sky. We were seeing it move at only a fraction of its maximum…

It’s difficult to fully grasp the enormity and extremity of Jupiter. The planet – a striped behemoth of swirling gas with around 100 moons, one of which is larger than Mercury – dominates the Solar System, flooding space with its magnetism and exerting its powerful gravity over everything nearby. The planet contains most of the ‘stuff’ left over after the birth of the Sun, and is so influential that it’s played a central role in shaping our patch of space into the system we see today. It’s no wonder that we’ve had Jupiter firmly in our sights from our earliest forays into space exploration. We first sent spacecraft there in the 1970s with NASA’s Pioneer and Voyager probes, which swung past the planet and observed it from space. NASA’s Galileo…

To make a planet, first you’ll need a massive, reasonably dense cloud of cold gas and dust. Luckily, later generations of the cosmos have provided just that. These clouds, rich in hydrogen, helium and elements forged in earlier stars, are the raw ingredients for planets. In the case of Earth, this happened about 4.5 billion years ago. So if you’re starting from scratch, you may want to clear your schedule for the next few aeons… Next, you’ll need something to give that cloud a cosmic nudge. A nearby supernova blast, a passing star or some other gravitational disturbance will do the trick. This triggers the cloud to begin collapsing under its own gravity. As it contracts, most of the mass falls towards the centre, forming a protostar. The rest flattens…

PICK OF THE MONTH Saturn Best time to see: 21 September, 01:00 BST (00:00 UT) Altitude: 35° Location: Pisces Direction: South Features: Rings, subtle atmospheric features, moons Recommended equipment: 150mm or larger Saturn reaches opposition this month on 21 September, rising to a peak altitude of 34° as seen from the centre of the UK. The planet is currently within Pisces, shining away, with a slightly off-white hue, at mag. +0.2 during opposition. On 8 September, it can be seen close to a 98%-lit waning gibbous Moon shortly after both objects rise and the sky darkens, at around 21:00 BST (20:00 UT). If you had a chance to catch a view of Saturn through a telescope last month, you would have seen the rings were narrow but obvious. At the start of August, the planet’s…

1. Psi Aquarii group This colourful grouping of stars spans nearly 5° of sky, from mag. +5.0 Psi3 (ψ3) Aquarii to mag. +5.6 96 Aquarii. The colours range from bluewhite mag. +5.5 Psi2 (ψ2) Aquarii (spectral type B) to orange-red mag. +4.2 Phi (φ) Aquarii (spectral type M), with all the intervening spectral types (AFGK) represented. Can you arrange them in colour order and identify which star is which spectral type? □ SEEN IT 2. M2 Our next target, the globular cluster M2, is easy to find due north of mag. +2.9 Sadalsuud (Beta (β) Aquarii) and due west of mag. +2.9 Sadalmelik (Alpha (α) Aquarii). It is obvious in a star-sparse region of sky and you may see it as Charles Messier himself did: “a nebula without stars.” If…

Sun, sangria and… solar eclipses? Over the next few years, Spain will offer front-row seats to some of the most spectacular celestial shows on Earth, with three ‘central’ – that is, total or annular – solar eclipses in less than 18 months. This astonishing sequence looks set to make it Europe’s eclipse-chasing epicentre for the rest of the decade. The standout is on Wednesday 12 August 2026: Spain’s first total solar eclipse in over a century, during which a short totality will briefly reveal to the naked eye the sun’s corona (Spanish for ‘crown’, incidentally), its tenuous outer atmosphere. On that date, a path of totality will pass over the Arctic, Greenland, Iceland, the Atlantic, a speck of Portugal and northern Spain. Occurring just before sunset, totality will last under…

The Messier Catalogue is one of the most well-known collections of astronomical objects. Compiled in the 18th century by French astronomer and avid comet hunter Charles Messier as a quick reference of non-cometary bodies he could ignore, today it serves as a comprehensive list of some of the deep sky’s most alluring objects to observe. Among its entries are various nebulae, star clusters and galaxies, but one entry in particular, Messier 102 (or M102), has sparked considerable controversy and debate within the astronomical community. M102 was originally recorded by Messier’s assistant Pierre Méchain in spring 1781. Méchain made many of the discoveries in the catalogue, which Messier usually confirmed before recording. However, under pressure to publish in the annual French almanac Connaissance des Temps, Messier entered M102 without a position,…

The Gaia (Global Astrometric Interferometer for Astrophysics) space observatory, launched by ESA in 2013 and deactivated in March 2025, was dedicated to recording star positions, distances and proper motions in unprecedented detail. It measured more than 1 billion stars down to magnitude +20, with positional accuracy as fine as 24 micro-arcseconds for the brightest stars – that’s equivalent to measuring the thickness of a human hair 1,000km (621 miles) away. Gaia’s data is being released in phases. Gaia DR1 (Data Release 1) appeared on 14 September 2016 and contained the positions and magnitudes for approximately 1.1 billion stars, as well as the positions and parallaxes for more than two million stars. Released on 25 April 2018, Gaia DR2 provided enhanced information for 1.3 billion stars and added 14,000 Solar System…

Capturing night-sky objects comes with its fair share of challenges. How you handle them can make the difference between a good image and a great one. Sometimes, when everything conspires against you getting a clean shot, post-processing is your only solution! For example, with some deep-sky, narrowband solar, or lunar images, parts of the frame will be very bright, while others will be darker and less defined. In lunar shots especially, details near the terminator can be particularly faint due to small shadows created by a low-angle Sun. These reduce the overall brightness in that part of the image. Because it only affects one area, it’s not easy to achieve an exposure that will reveal faint details without blowing out the brighter regions farther from the terminator. This image of…

Is it a bird? Is it a plane? No, it’s a mysterious interstellar interloper spotted passing through our Solar System. The comet, named 3I/ATLAS, was discovered by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS) survey telescope. Currently 675 million km (420 million miles) away, it could be the oldest comet ever seen. “Rather than the quiet Wednesday I had planned, I woke up to messages like ‘3I!!!!!!!!!!’,” says Matthew Hopkins, one of the astronomers who discovered the comet. Hopkins and the team developed the Ōtautahi–Oxford model to predict the properties of interstellar objects based on their orbits and possible origins. Non-interstellar comets, like Halley’s Comet, formed within our Solar System and are no older than the Solar System’s 4.5-billion-year lifespan. Interstellar visitors, however, are not formed around the Sun and…

A citizen astronomy project known as Kilonova Seekers has discovered an exploding star system in real time. Described as like a game of astronomical ‘spot the difference’, the project invites members of the public around the world to compare images of the night sky to images of the same section taken on previous nights. This time, the difference was an extremely bright exploding star. The explosion caused the star to brighten by a factor of 2,500. The fast response of participants meant that an unusually complete set of observations could then be made, including spectroscopy, X-ray and UV measurements. The wealth of data resulted in the discovery of what’s called a ‘period bouncer’, a type of cataclysmic variable star, now named GOTO0650. Cataclysmic variable stars fluctuate dramatically and unpredictably in…

Email us at inbox@skyatnightmagazine.com MESSAGE OF THE MONTH This is my photo (right) taken on 27 June 2025 at 03:46 MST, just two minutes before astronomical twilight, the very start of early dawn. It shows the Pleiades star cluster rising over the Tucson Mountains. What’s most exciting is that lone sixth-magnitude ‘star’ closest to the ridgeline on the far right of frame: it’s the planet Uranus! I’ve viewed Uranus through my 8-inch Celestron many times, but photographing it is hard. It was completely invisible to the naked eye under these (albeit early) twilight conditions. I used an Android Pixel 8 Pro smartphone mounted on a tripod, with 5x magnification and a three-second exposure in Night Sight mode, an ISO around 1000, and a remote shutter release. I calculated that Uranus…

Every time the Rubin camera captures a new patch of sky, it generates a fresh stream of data about the Universe. While this will be a massive treasure trove for astronomical research, handling it poses a unique challenge. Previous astronomical surveys, such as the Sloan Digital Sky Survey, used software designed for large datasets, but nothing on the scale that Rubin demands. With a 3,200-megapixel image captured roughly every 30 seconds, the observatory will generate about 20 terabytes of data a night, requiring a complete rethink of how astronomical data is handled. “It was a giant effort over a decade,” says Ivezić. The key lies in its modular design. The camera has 189 sensors, each of which splits its image data into 16 parts when it’s time to read out…

Come 2031, a pair of new robotic explorers will be investigating Jupiter and its moons: ESA’s Jupiter Icy Moons Explorer (Juice, for short) and NASA’s Europa Clipper, both of which are currently winging their way through the Solar System on their way to the giant planet. Juice is due to arrive at Jupiter in July 2031 and will explore the entire Jovian system before honing in on Jupiter’s three large and likely ocean-bearing moons: Europa, Ganymede and Callisto. The subsurface oceans on these moons may contain the building blocks for life, making them especially exciting in our hunt for habitable worlds other than Earth. Towards the end of its mission, Juice will hop over to Ganymede, making it the first spacecraft ever to orbit a moon in the outer Solar…

Mercury Best time to see: 1 September, 30 minutes before sunrise Altitude: 5.5° (low) Location: Leo Direction: East-northeast Mercury is a morning planet at the start of the month, rising 70 minutes before sunrise. On 3 September, the mag. –1.6 planet sits 1.6° from Regulus (Alpha (α) Leonis), the pair visible in the dawn twilight from around 05:40 BST (04:40 UT). Mercury is tricky to see after this, moving to superior conjunction on 13 September and thereafter poorly positioned for the rest of the month. Venus Best time to see: 19 September, 12:00 BST (11:00 UT) Altitude: 45° Location: Leo Direction: South-southwest Mag. –3.8 Venus is a morning planet 1.4° south of the Beehive Cluster, M44, on 1 September. On this date, it rises 3 hours before the Sun at 03:20 BST (02:20 UT), giving an…

Comet C/2024 E1 (Wierzchoś) is set to be a slow burner throughout the autumn, rising from a dim 13th magnitude at the start of September to possibly mag. +5 at the start of 2026. Sadly, at its brightest it will be in southern Sagittarius, too low and too close to the Sun to be seen properly from the UK. But that doesn’t mean we can’t enjoy the show until mid-November, by which time the comet will hopefully be approaching eighth magnitude. This is a hyperbolic comet inbound from the Oort cloud. It was discovered in March 2024 by the Polish astronomer Kacper Wierzchoś during a routine survey at Mount Lemmon Observatory in the Santa Catalina Mountains, Arizona. It was captured by an f/1.6, 1.5-metre Cassegrain telescope using a 111.5MP CCD…

Star and deep-sky catalogues are crucial resources for making sense of the night sky. There are a lot of them, though – so many, in fact, that you almost need a catalogue of catalogues to keep track of them all! There’s a rich history wrapped up in the creation of these databases, and many astronomical objects appear in multiple catalogues, each with its own naming convensions and quirks. In this guide, we’ll explore some of the widely used catalogues and the types of celestial objects they cover, from nearby stars to distant galaxies. With massive amounts of high-precision data now streaming into mainstream planetarium apps, what role do older catalogues play? Stars and deep-sky objects may not change rapidly, but when it comes to pinpoint accuracy, even small shifts can…

Guiding is essential for deep-sky astrophotography, because even the most precise setups can introduce small tracking errors that affect your images. These are caused by a mix of mechanical flaws, imperfect polar alignment and atmospheric effects, all of which can cause stars to drift during long exposures, resulting in elongation or blur. By using guiding accessories and specialist guiding software, such as the free PHD2, you can continuously monitor a reference ‘guide’ star and send corrective commands to your mount. This will keep your stars pinpoint-sharp, allowing much longer exposures. Longer exposures mean dramatically improving sharpness and depth, revealing faint details in nebulae, galaxies and star clusters. Guiding involves mounting a small, secondary telescope (called a guide scope) and a sensitive camera (guide camera) alongside your main imaging telescope and…

PHOTO OF THE MONTH The Clamshell Nebula Nicole Poersch, Prestwick, South Ayrshire, UK, 15 September 2024–21 January 2025 Nicole says: “The Clamshell Nebula in Cygnus is often overlooked due to its proximity to the North America and Pelican Nebulae. It’s also very faint: this image required over 63 hours of exposure, spread over 22 nights.” Equipment: ZWO ASI1600MM camera, William Optics Zenithstar 73 II refractor, iOptron CEM25P mount Exposure: R 55× 40”, G 50× 40”, B 50× 40”, Ha 149× 600”, OIII 110× 600”, SII 113× 600” Software: PixInsight Nicole’s top tips: “I began astrophot ography in 2021, knowing it would take trial and error. I never imagined one of my photos would appear in a magazine, let alone win Photo of the Month! My top tips: believe in yourself,…