Sky notes for 2025 October & November

2025 October 1

Nick Hewitt

With Pegasus flying high and the rest of the Perseus-Andromeda legend on show, this is indeed the season of myths and mellow fruitfulness. Cepheus and Cassiopeia, Andromeda’s vain and unwise parents, await the arrival of heroic Perseus – bearing the lopped head of the Gorgon Medusa – to turn the sea monster Cetus to stone. The tale always captivates youngsters and is fun to share at star parties.

With Ursa Major finding a spot for hibernation in the north, and Orion yet to ascend, our best signpost to the autumn constellations is the winged horse itself, its great square serving as a guide to the relatively inconspicuous watery constellations immersed beneath it: Aquarius, Pisces, Piscis Austrinus and Cetus. The southern aspect of the autumnal sky may be the least glittering of the four seasons, but it still offers plenty of interest.

The deep sky

Pegasus has an added claim to fame this season: 2025 Oct 6 marks 30 years since Swiss astronomers Didier Queloz and Michael Mayor announced the discovery of the first confirmed exoplanet around a Sun-like star, 51 Pegasi, just west of the Square of Pegasus. Queloz and Mayor shared the 2019 Nobel Prize for this work. Despite its faintness (magnitude 5.49), the significance of 51 Pegasi is highlighted by its formal name, Helvetios, bestowed in honour of the astronomers. Its planet is a hot Jupiter: although only about half Jupiter’s mass, it orbits so close to its star that it is roasted to 1,500 K! Its detection forced a revision of planetary formation theories and launched a surge in the new discipline of exoplanetary science, pursued with satellites, professional terrestrial observatories, and even by the amateur community. By 2025 Jun, 5,926 confirmed exoplanets had been identified in 4,419 planetary systems, with thousands more candidates awaiting confirmation.

Using Pegasus as a signpost, follow a line from beta Pegasi (Scheat) through alpha Pegasi (Markab) and arrive at Fomalhaut in Piscis Austrinus, the southern fish. At magnitude 1.16, it is the most southerly first-magnitude star visible from the UK. Fomalhaut stands out in an otherwise dull region of sky, but it gained fame in 2005 and 2008 when the Hubble Space Telescope imaged what appeared to be an exoplanet – later named Dagon – orbiting within a cold dust ring around the star. However, continued study has all but disproved its planetary status: Dagon is now thought to be a transient debris cloud, a conclusion recently confirmed by the James Webb Space Telescope.

Being so low in declination, there is not very much of note within Piscis Austrinus, and even if it were higher, it would still be dull. For serious galaxy enthusiasts, there are a couple of Arp galaxies in the northern aspect, on the Aquarius border. NGC 7314 (Arp 14), a 10th-magnitude spiral about 5 × 2 arcmin in size, can be located by following Fomalhaut through epsilon Piscis Austrini to its northwest. Continue the line further to reach the close pair NGC 7284/5 (Arp 93), much fainter at magnitude 12.9 and smaller at 2.3 × 1.8 arcmin.

Moving northwards to less taxing quarry, we find the zodiacal fishes, Pisces. The constellation is a sprawling pair of fishing lines adjoined at a knot marked by the alpha star Alrescha. No star in Pisces is brighter than 4th magnitude, and the easiest asterism to recognise is the Circlet of Pisces to the west, nestling under Pegasus. It requires a transparent night to make it out easily. From the Circlet, the fishy stream flows eastward to Alrescha before turning sharply northwest to nibble at Andromeda. Along this route lies eta Piscium, and slightly northeast you might hope to detect Messier 74 (M74; Figure 1, p. 358) – one of Messier’s trickier galaxies. This beautiful face-on ‘grand design’ spiral is hard visually, although Mechain discovered it in 1780, and Messier confirmed it soon after. Spiral structure was noted by Lord Rosse in 1844, but it was not confirmed as a spiral nebula until photographed by H. D. Curtis at Lick Observatory in 1914. Until then, it had been misclassified as a globular cluster. Despite its seemingly bright magnitude (8.9), it has low surface brightness and only the central core is visible without the darkest and clearest skies. Large-aperture telescopes will show spiral arms spanning 10.5 × 9.5 arcmin. It is thought to be 32 million light-years away.

To the east of Pisces, and at the same declination as Alrescha, lies the head of the whale, Cetus, marked by another circlet – this one brighter. The most prominent star is the red giant Menkar (alpha Ceti, magnitude 2.5) to the east, with lambda, mu, zeta and gamma Ceti completing the asterism. Delta Ceti forms a shallow triangle with Menkar and gamma, and just to its southeast lies our nearest Seyfert galaxy, M77 (Figure 2, p. 358). Found by Mechain in a golden seam of discovery in 1780, it is a tight spiral of magnitude 8.9. Spanning 7 × 6 arcmin, it has a much higher surface brightness than M74, and its core is visible in 10 × 50 binoculars. Lord Rosse noted its spiral structure in 1848, but he was not sure whether it was a spiral nebula or star cluster. In 1908, spectroscopy suggested the presence of bright, broad emission lines, and these were confirmed by Vesto Slipher at Flagstaff in 1917. It is the prototype of Seyfert galaxies with bright nuclei and broad emission line spectra. It is also a powerful radio source, with alternative designations Cetus A and 3C71.

Nearby is NGC 1055 (see image at top of p. 358), one of the best edge-on spiral galaxies in the sky, featuring a prominent nuclear bulge. At magnitude 11.4 and extending 7.6 × 2.7 arcmin, it is challenging visually but poses well for imagers. The proximity of two 7th-magnitude stars to the north help pinpoint this galaxy.

Cetus is a vast constellation – the fourth largest of the 88 – and hosts the famous variable star Mira, southwest of delta Ceti. Most other objects of interest are galaxies, but one notable exception is the large planetary nebula NGC 246 (Figure 3, p. 359), sometimes nicknamed the Skull Nebula. Its 8th-magnitude glow was first detected by William Herschel in 1785. It is 225 arcsec in diameter and round, although its southern and eastern edges are less well defined. The central star is 12th magnitude and two other stars sit within the complex, mottled disc.

Almost nine degrees due south of the Skull Nebula lies another fine galaxy, NGC 247 (Figure 4). Drop past Diphda (beta Ceti, the brightest star in Cetus at magnitude 2.0) but stay in the same right ascension as NGC 246; just north of a triangle of 5th-magnitude stars, the galaxy can be found. It is a large (21 × 7 arcmin), tilted spiral, with an unusual ‘hole’ to the north, probably an illusion caused by the configuration of its spiral arms. It belongs to the Sculptor Group and lies 11.5 million light-years distant. To the northeast, a faint line of galaxies known as Burbidge’s chain is visible through large-aperture telescopes. Although designated NGC 247A, NGC 247B, and so on, these galaxies are unrelated to NGC 247 itself and lie far beyond the dusty spiral. At around magnitude 17, they are well within range for imagers.

For UK observers, many of these targets lie low in the sky, so let us escape the water and move north. Another popular face-on spiral is the magnificent M33 (Figure 5), the third-largest galaxy in the Local Group after the Milky Way and M31 (Andromeda). Its apparent diameter, 67 × 41 arcmin, is larger than the full Moon’s, but the small nucleus and low-surface-brightness spiral arms make it tricky to discern. With large apertures and low power, the many H ii regions stand out, and in images, the young stars in the spiral appear markedly blue.

M33 is so fascinating that other fine galaxies in Triangulum can be overlooked. One such example is NGC 925 (Figure 6), easily located east of gamma Trianguli on the Triangle’s base. This 12 × 7 arcmin, 10th-magnitude, tilted galaxy appears as a spindle visually, but the difficult spiral arms emerge beautifully when imaged.

The solar system

Moon & Sun

British Summer Time ends on Oct 26, a month after the equinox, ushering in darker evenings – which suit many observers. The Sun was quiet in May and June but revived somewhat later in the summer with multiple small sunspots visible in white light. It will be interesting to see whether this enhanced activity persists into late autumn.

There are no eclipses during this period.

Planets

October is a poor month for observing the terrestrial planets but marvellous for the gas and ice giants.

Mercury, following its September superior conjunction, is poor in October evenings but becomes a good morning target at the end of November until reaching inferior conjunction on Nov 20. Its best showing will be in the first few days of December.

Venus continues to shine brightly in the morning sky throughout October, though it becomes difficult in November and reaches superior conjunction on 2026 Jan 6. Its magnitude remains a constant −3.9, even as its gibbous disc shrinks from 11 to 10 arcsec while moving from Virgo to Libra during the two months.

Mars remains unavailable, appearing tiny and faint as it heads toward solar conjunction in 2026 Jan.

Saturn (Figure 7) is the focus of attention, now nicely placed in the evenings on the Aquarius–Pisces border. It passed opposition on Sep 21, and although rather dull and yellowish, at magnitude 0.6 it stands out in a relatively barren starfield beneath Pegasus and the Circlet of Pisces. The rings are now too edge-on to be seen easily, as the planet’s tilt is less than a degree as seen from Earth. As a consolation, the motions of Saturn’s moons are easier to track, especially cloudy Titan. It transits Saturn’s northern aspect on Oct 6 (after midnight) and Oct 21 (just before midnight). There are also occultations as Titan disappears behind Saturn’s southern hemisphere. See the BAA Handbook for more details.

Jupiter rises by late evening in October, a magnificent sight in Gemini at magnitude −2.4. It is available all evening in November, although it does not reach opposition until 2026 Jan 10. This apparition should not be missed, as it is so protracted and with the gas giant so well placed.

Uranus (Figure 8) remains in Taurus, south of the Pleiades, and is at opposition on Nov 21. It is optimally placed for observation, and its orientation makes its five brighter moons accessible.

Neptune was at opposition on Sep 23 in Pisces and lies a little northeast of Saturn in November. This is a good season to track down 13th-magnitude Triton, by far the brightest of Neptune’s moons.

Among the dwarf planets, (1) Ceres, the brightest (7.7), is at opposition on Oct 3 while swallowed by Cetus. Its retrograde motion is quite notable and easily followed in binoculars.

Meteors

The Camelopardalids peak on Oct 6, but the showing is unfavourable as the Moon is full the following day.

The Southern Taurid maximum is on Nov 5, but unfavourable as the full Moon will spoil the view, even if terrestrial fireworks do not. The Northern Taurids peak just a week later, so observation should be satisfactory until midnight, before the Moon rises. However, both showers are active between mid-September and early December. The Southern stream is swift, often with persistent trains, while the Northern is slower, so easily distinguishable despite both radiant points lying close to the Hyades cluster.

The new Moon will not compromise the Orionids’ peak on Oct 20, although their maximum is broad. These speedy meteors derive from Comet 1P/Halley.

It is now 26 years since the marvellous Leonid display of 1999 Nov. With a 33-year cycle, the next potential Leonids storm is due in seven years. This year’s maximum falls on Nov 18, with no lunar interference. The shower is derived from Comet 55P/Tempel–Tuttle.

Comets

The third known interstellar comet, 3I ATLAS or C/2025 N1 (ATLAS), passes through Virgo from east to west after perihelion in October, but is too close to the Sun to be visible from the UK. From mid-November, it may reach 11th or 12th magnitude as a morning object, moving into Leo by December, although fading rapidly.

The season’s most promising comet is C/2025 A6 (Lemmon), discovered on 2025 Jan 3. It reaches perihelion on 2025 Nov 8, and emerging from its recent solar conjunction, is brighter than predicted. It could reach magnitude 5 in late-October evening skies. On Oct 21, when the Moon is new, it will be low and lying near epsilon Boötis, between Alkaid and Arcturus. For more details, see Nick James’ summary at tinyurl.com/aac4mcc9.