Sternenhimmel Juli 2026

Bresser July Sky Guide

Sky chart showing the night sky for July 2026 at 51 degrees North latitude.

Midsummer has come and gone for those of us in the northern hemisphere. Nights will very gradually start to get longer again. Many of us will still be experiencing permanent Astronomical Twilight, which always occurs around the Solstice, meaning the sky never fully darkens. From mid-July, those around 50° north will start to experience true darkness again. Though the duration of this twilight extends further in time, the further north you find yourself: Manchester experiences it from mid-May to late July, Edinburgh from early May to early August and Reykjavik in Iceland from early April to early September.

No matter where you find yourself in the world, as ever, there’s plenty to see in the sky above us this month…

The Solar System

The Sun

May’s number of recorded Sunspots was pretty much “on the money“ for predictions at this point in the solar cycle (101.4 recorded, to the predicted 101.1). This is an improvement from the beginning of the year’s recordings, which were 15-20% down on February, March and April’s predicted numbers. The Sun is clearly slowing from the Summer of 2024’s significantly higher than expected Sunspot numbers. Although solar activity can rise and fall from month to month throughout the cycle, so (as mentioned in previous sky guides) it is often difficult to judge exactly when a peak has been reached. We can now see, with the benefit of some hindsight, that the period May to October 2024 was the peak of this latest solar cycle.

With regard to auroral activity, the most significant period occurred between roughly 3rd and 9th June. NOAA issued geomagnetic storm watches after modelling the arrival of multiple Earth-directed CMEs. Forecasts initially suggested the possibility of G3 (Strong) storm conditions and there was discussion of a potential G4 level if CME interactions proved favourable. Although the ultimate geomagnetic response was somewhat weaker than some early projections, the event nevertheless produced enhanced auroral visibility across middle latitudes.

Websites such as www.spaceweather.com and Michel Deconinck’s monthly newsletter (Aquarellia Observatory Forecasts) cover various aspects of solar observations and provide valuable insights into the current state of the Sun. Signing up for the AuroraWatch app, developed by Lancaster University in the UK, is also highly recommended for those seeking advance warnings of impending auroral events.

NOAA latest sunspot chart showing recent and predicted sunspot activity for the current solar cycle.

NOAA latest sunspot chart. Public domain.

The Moon

The Moon begins July at a Waning Gibbous phase, just a couple of days past Full and as such illuminated by a healthy 97%. A resident of Sagittarius at this point, it is lying deep in the southernmost part of the ecliptic and atmospheric lensing will cause the Moon to appear slightly larger than it would, when found further up in the sky. Naturally, those readers in the southern hemisphere will have the completely opposite experience, with the Moon riding high in the sky at near Full at this time of year. Being so well illuminated, the beginning of the month will not be an optimum experience for deep sky observers and imagers - and this will only be compounded by the lighter skies that those in the temperate northern hemisphere will be experiencing.

The Moon will travel through Sagittarius, into Capricornus and then Aquarius, where it will pass Neptune, before reaching Last Quarter phase on the 7th, in Pisces. The Moon will sit around 6° to the north of Saturn in the morning sky, with both worlds rising around midnight.

The next week sees the Moon creeping towards the Sun and decreasing its phase rapidly as it does. Moving from Pisces, through Aries and Taurus and then on into Gemini, where it meets the Sun and becomes New on the 14th. The Moon will track to the north of the Sun and will then become an evening target.

Passing the very low-lying Jupiter, in Cancer, the Moon treks across Leo, passing the brilliant Venus on the evening of the 17th. The two bodies will be separated by just under 4° and will be a striking pair in the early evening sky.

After this, the Moon will continue its journey through Leo and on into Virgo, where it will reach First Quarter phase on the 21st. The Moon crosses the border into neighbouring Libra the next day and spends the next few days quickly passing through Scorpius, Ophiuchus and Sagittarius. It will then emerge from the deepest part of the southern ecliptic to become Full on the Sagittarius/Capricornus borders on the 29th. While skies will start to become darker for some due to the reimposed true astronomical darkness, the end of the month won’t be best for deep sky observations and imaging.

The Moon ends July in Capricornus, at a Waning Gibbous phase of around 98% illumination. The Moon will rise at a little before 10 pm (BST), transiting at just before 2:30 am and setting at 7:30 am the following morning.

Sky chart showing the Moon, Neptune and Saturn in the morning sky at sunrise on 7th July 2026.

Mercury

Mercury begins the month fading rapidly into the evening twilight, following its excellent June apparition. At the beginning of the month it is already faint and practically impossible to observe, eventually disappearing completely from view as it reaches inferior conjunction on 12th July. At this point Mercury passes between the Earth and the Sun and transitions from an evening object to a morning one.

At this stage Mercury would theoretically present its largest apparent diameter of the apparition, around 11.7 arc seconds, but it is entirely unobservable due to its proximity to the Sun. At this point in time, Mercury is easily the closest planet to us, at approximately 0.57 AU from Earth at conjunction point. Indeed, Mercury spends most of its time being the closest planet to us in the solar system, despite both Venus and Mars’ orbital proximity.

Following conjunction Mercury moves rapidly west of the Sun and begins to emerge into the dawn sky. Northern Hemisphere observers are particularly favoured during this apparition, due to the geometry of the “rising” ecliptic at this time of year, which places Mercury at a relatively steep angle to the eastern horizon before sunrise. By the final week of July the planet becomes increasingly easy to locate in morning twilight.

From around 22nd July onwards Mercury should be visible low in the east-north-east approximately 45 to 60 minutes before sunrise. On the morning of the 22nd the planet stands roughly 8 degrees above the horizon at sunrise, rising to around 14–15 degrees by the end of the month. During this period Mercury brightens dramatically as its illuminated phase increases. Although still showing a crescent phase through a telescope, its visibility improves noticeably with each passing morning.

Observers using small telescopes will find the final week of July particularly rewarding. Mercury displays the familiar phases first observed by Galileo - changing from a thin crescent shortly after conjunction to a thicker crescent, as it approaches half phases (dichotomy). Around 31st July, the 8.1 arc second diameter planet presents a phase of approximately 32% illumination and shines at around magnitude +0.45.

While Mercury’s greatest western elongation does not occur until 2nd August, the last days of July provide an excellent opportunity to begin following the planet’s morning apparition. At greatest elongation, Mercury will stand almost 20 degrees west of the Sun, at an altitude of around 12° (as observed from 51° north) and this apparition is regarded as one of the more favourable morning appearances of 2026 for observers in northern latitudes.

Sky chart showing Mercury low in the east-north-east at sunrise on 31st July 2026.

Venus

Venus is a brilliant fixture in the evening sky throughout July, shining prominently in the west after sunset as the familiar Evening Star. At the beginning of the month, the planet shines at magnitude -4.1 and lies approximately 41° east of the Sun. Through a telescope, Venus appears as a gibbous disc around 16 arc seconds in diameter and approximately 69% illuminated.

During the first week of July, Venus continues to climb away from the Sun, as it moves steadily towards its greatest eastern elongation on 15th August. As a result, the planet remains visible for progressively longer after sunset and becomes increasingly well placed for observation from mid northern latitudes. However, as the planet is now past the point of the highest node of the northern ecliptic, as time progresses, it does appear to sink a little lower in the sky each evening.

On 9th July, Venus passes less than one degree north of Regulus, the brightest star in the constellation Leo. The close pairing creates an attractive sight in the western sky after sunset, with Venus appearing vastly brighter than the distant star.

As the month reaches its midpoint, Venus continues to grow in apparent size as it moves closer to Earth. The evening of the 15th finds the planet at a diameter of 18 arc seconds. At the same time, its illuminated phase gradually decreases, making the changing shape of the planet more apparent through telescopes.

A particularly attractive conjunction occurs on the evenings of 16th and 17th July when a slender waxing crescent Moon appears close to Venus in the western sky. The pairing will be visible shortly after sunset and should provide one of the month’s finest opportunities for wide-field astrophotography.

Throughout the second half of July, Venus becomes increasingly conspicuous against the evening twilight. Its apparent diameter continues to increase while its illuminated fraction slowly decreases, producing a noticeably changing appearance for those following the planet from week to week.

By the final week of the month, Venus, while sitting a little lower in the sky than it did at the beginning of the month at just under 15° elevation at Sunset (as observed from 51° north), still dominates the western sky after sunset and remains visible for around two hours after sundown from most mid northern latitudes. The planet has grown to approximately 20 arc seconds in apparent diameter, while its illuminated fraction has fallen to around 56%, giving it a noticeably larger and less fully illuminated appearance than at the beginning of July.

As July draws to a close, Venus approaches an elongation of nearly 46° from the Sun ahead of its greatest eastern elongation on 15th August. While its shrinking altitude in the evening sky decreases the quality of higher power telescopic views of Venus, the planet still ranks as the most impressive evening object at present and provides an excellent opportunity to observe the changing phase of Earth’s planetary neighbour over successive nights and weeks. Venus ends July on the 31st as a -4.2 magnitude target, displaying an apparent size of 20.8 arc seconds and sitting around 13 1/2° above the horizon (again, as observed from 51° north), as the Sun sets.

Sky chart showing Venus and the Moon in the western sky at sunset on 16th July 2026.

Mars

Mars remains a rather diminutive morning object, sitting a few degrees underneath the Pleiades, in Taurus, at this time of year. At +1.3 magnitude it will hardly be exceptionally notable in the glare of the dawn sky. Indeed, it’s currently nearly half a magnitude fainter than Aldebaran, Alpha Tauri, with which it shares a constellation.

Mars is pulling away from the Sun (from our vantage point here on Earth) and increases its separation from just under 38° at the month’s beginning to just under 45 1/2° at July’s end. At 4.7 arc second diameter and a still rather feeble +1.3 magnitude at the end of the month, we will have to wait until the latter part of the year for any great change in the Red Planet’s visual demeanour.

Sky chart showing Mars near the Pleiades in Taurus at sunrise on 1st July 2026.

Jupiter

While technically just about still observable above the horizon in the evenings at the very beginning of July, Jupiter is dropping rapidly sunward and despite a healthy -1.8 magnitude brightness, becomes practically unobservable towards the end of the month. The planet reaches superior conjunction on July 29th. After this, it will re-emerge as a morning target, though it will be a month or so before it is at a reasonable height again.

Saturn

Saturn is arguably the best placed of the major planets for observation during July. The morning of the 1st finds Saturn a resident of Pisces, shining as a steady +0.8 magnitude and displaying a 17.5 arc second diameter disc. It reaches an elevation of just over 33 1/2° at daybreak (as observed from 51° north).

By mid month, Saturn has brightened fractionally to +0.7 magnitude and now displays a 17.9 arc second diameter. It will rise a little after midnight and will now stand at just under 40° elevation at sunrise.

Towards the latter part of the month, Saturn starts to go retrograde in terms of perceived motion in the ecliptic. As long-term readers will remember, this is the precursor to opposition for all planets which orbit outside the Earth’s orbit and as such, is a rather welcome event. As we’ve mentioned before, the planet is in no way changing its orbital direction, rather we on Earth are catching it up on our faster interior orbit and when this occurs the planet appears to move backwards from our perspective. This is often referred to with the analogy of overtaking a slower car when both cars are travelling in the same direction. Although the slower overtaken car is in no way changing its direction, it will appear to start to go backwards from the perspective of the occupants of the faster car. This is exactly what’s happening to Saturn, as observed from Earth at the end of July. Although Saturn is not at opposition until early October, this retrograde motion is a sign that we are entering into the best observing phase of the planet during 2026.

By the end of July, Saturn has brightened yet further to +0.6 magnitude and now displays an 18.5 arc second diameter disc. The planet will rise a little after 11 pm and transit at around 5:30 in the morning. At this point, the planet will sit at just below 43° elevation above the horizon (again, as observed from 51° north).

Sky chart showing Saturn going retrograde on 27th July 2026.

Uranus and Neptune

Uranus is located a few degrees to the west of Mars in Taurus, in the morning sky at the beginning of July. Being much fainter than Mars at +5.8 magnitude, it will be nigh on impossible to pick out in the morning twilight. While the planet increases its separation from the Sun as the month progresses, it will be a little while longer before it’s in a more acceptable place for telescopic observation.

Neptune is considerably further separated from the Sun than its neighbour and sitting in reasonable proximity to Saturn in Pisces will be much easier to locate than Uranus. At +7.9 magnitude, it is always a challenge to find, but especially with darkest skies returning towards the end of the month for many in the temperate northern hemisphere from then on, Neptune should be more readily observable in the early morning sky.

Sky chart showing the relative positions of Uranus and Neptune at sunrise on 15th July 2026.

Comets

The highlight of July in terms of comets is the peak and brightness of the periodic comet 10P/Tempel 2. This comet has a 5.5 year orbital period and has been observed many times since its discovery in the 19th century. The comet will peak in brightness towards the end of July and will possibly be around 7th magnitude by then. This will not be a naked eye object, but should be observable under dark skies with larger binoculars and telescopes. Sadly, the Full Moon’s appearance towards the latter part of the month - particularly in the area of sky the comet is in - is not an optimal situation as far as observations are concerned. However, the comet will stick around within the Aquarius and Capricornus regions for most of July, so particularly mid-month will be a reasonable time to try to find and image it.

Sky chart showing the path of Comet 10P/Tempel 2 during July 2026, with the comet and Moon position shown on 1st July.

Meteors

For July 2026, the first early members of the annual Perseid meteor shower will begin to appear during the latter part of the month, ahead of the shower’s main peak in August. Although Perseid activity will still be relatively low, keen observers may catch occasional bright meteors.

The principal meteor shower of July remains the Southern Delta Aquariids, which peak around the nights of 28–29th and 29–30th July. Under ideal dark-sky conditions the shower can produce around 15–20 meteors per hour, although actual rates seen from the temperate northern hemisphere are usually lower, due to the radiant in Aquarius remaining relatively low above the southern horizon. The best viewing time is after midnight and into the pre-dawn hours when the radiant climbs highest. Meteors can appear anywhere in the sky despite originating from the direction of Aquarius.

For 2026, moonlight will be a significant factor. The Full Moon occurs on 29th July, coinciding closely with the shower’s peak, meaning bright lunar illumination will wash out many of the fainter meteors. Observers should therefore concentrate on the hours before moonrise where possible or seek locations with unobstructed horizons and minimal artificial light. Only the brighter Delta Aquariids and early Perseids are likely to stand out well against the moonlit sky.

The Delta Aquariids are relatively slow meteors, entering the atmosphere at about 41 km/s, and are generally less bright than the Perseids. The shower is associated with Comet 96P/Machholz and has shown occasional indications of enhanced activity due to fragmentation of the parent body. Wide-field photography remains the most effective way to record the shower, whether using a DSLR or mirrorless camera with a wide-angle lens, or an all-sky camera system.

When observing around the end of July, it is worth remembering that both Delta Aquariids and early Perseids may be visible. If a meteor’s path is traced backwards, its apparent point of origin can be used to determine which shower produced it.

Sky chart showing the Delta Aquariid radiant in Aquarius during July 2026.

Noctilucent Clouds

Noctilucent Clouds are often seen in July - their bright gossamer/web-like structures can normally be seen low on the northerly horizon, between latitudes of 50-65 degrees, when the Sun is between 6 and 16 degrees below the horizon. These clouds are mysterious - there were no recorded sightings of them before 1885. Some researchers believe they are formed as a result of volcanism, human-induced atmospheric pollution, or even the condensation of water vapour along the trails of meteors. Interestingly, a significant link between the power of the Northern Polar Stratospheric Vortex and the production of NLCs in the Southern Polar Mesosphere (the atmospheric layer above the Stratosphere) has been found by analysis of ground based data and that gleaned from NASA climate satellites. It would appear that when the Northern Polar Vortex is particularly strong, this negatively affects the production of NLCs over the Southern pole over 12,000 miles away. These interconnections are a sure sign of how little we truly understand the mechanics of the atmosphere of our home planet and how much is still potentially to be uncovered.

Whatever their origins, now is the best time to see NLCs from Northern latitudes. Interestingly, whilst Noctilucent Clouds have been observed in the Southern Hemisphere, their incidence appears much fewer than their Northern Hemispherical counterparts.

Deep Sky Delights in Northern Sagittarius and Serpens Caput

July is not the best time for observing really challenging Deep Sky objects from the Upper Northern Hemisphere, due to the Summer Solstice and the lack of true astronomical darkness, but there's still plenty to see, even if the sky is not at its darkest. While we are normally rather Northerly-biased in the sky guide, this month, as we promised in June’s sky guide, the emphasis is most definitely on a particularly rich part of the southern sky - the northern parts of Sagittarius and neighbouring Serpens Caput.

The area of sky we will cover is pretty small - a patch of around 12 by 8 degrees, covering most objects of interest. This is just slightly larger than the southern part of Orion, including the belt area. While Orion is not short of interesting targets, this area of sky is littered with them. This engrossing part of the sky sits just to the north of the so-called “teapot” asterism of stars which make up the central part of Sagittarius. Although this area of sky sits very low for northern hemisphere observers, it is still not impossible to observe them well from higher latitudes. All of these targets are readily visible in decent binoculars from a reasonably dark site and many of the brighter ones are visible in distinctly more challenging areas of light pollution.

Sky chart showing Sagittarius and Serpens Cauda with deep sky objects including Messier clusters and nebulae.

Starting just north of the line between Nunki, Sigma Sagittarii, the second brightest star in the constellation, marking the top of the handle of the “Teapot”, and its neighbour Kaus Borealis, Lambda Sagittarii, we come to the jewel of the Sagittarian globulars, the lovely M22. At +5.09 mag, this cluster outshines all the others in its class, bar Omega Centauri and 47 Tucanae. Lying on the plane of the Milky Way means this cluster is probably not as well-defined and noticeable in its particular location as it would be were it in another, darker part of the sky. However, an observer can still make out M22 from a dark location with the naked eye. Through a telescope or binoculars it is stunning - an elliptical blizzard of stars, easily resolved in all types of optics, though it is true that its core is not particularly well-condensed. At 6.7 arc minutes across, M22 is larger than most globulars, including 47 Tucanae. Only the massive Omega Centauri, at 10 arc minutes across, is appreciably bigger.

M22 may have been recorded by Hevelius, but its discovery is normally credited to the 17th century German Astronomer Abraham Ihle, who first reported it in 1665. Halley included it as part of his 6 nebulous objects of 1715. Messier found and cataloged M22 on June 5th 1764.

The reason for M22’s comparative brightness has nothing to do with its physical dimensions - at 97 light years diameter and 210,000 solar masses, it is quite average. M22 is so bright and large because it is close to us as globulars go - around 10,000 light years from Earth.

Hubble Space Telescope image of Messier 22, a globular star cluster in Sagittarius.

Messier 22, HST Image. Image credit: NASA/ESO, Public Domain.

2 1/2 degrees from M22 to the SW sits the aforementioned Kaus Borealis. This star marks the tip of the “Teapot’s” lid and also provides a useful star hopping point for the next globular Sagittarius has on offer - M28. This globular can be found a little under a degree to the west of Kaus Borealis. M28 is a little less bright and large than its neighbour, but is a lovely object in its own right. At +6.78 and just under 4 arc minutes diameter, M28 lurks on the very limit of human naked eye resolution. By all means attempt to find it without binoculars or telescope, but you will need a very, very dark location and good night adaption in order to make the attempt. However, in binoculars and telescopes, M28 really delivers. More compact and condensed than M22, M28 has a distinct core, surrounded by a halo of looser granular stars. Binoculars will pick up this granularity, but won’t resolve individual stars - a larger telescope, probably 8-inches +, will.

M28 was discovered by Messier at some point in July 1764, a month after its neighbour M22. It is now known to lie some 18,000 light years away from us and be around 60 light years in diameter. Again, like M22, M28 is a cluster well worth seeking out.

Hubble Space Telescope image of Messier 28, a globular star cluster in Sagittarius.

Messier 28, HST Image. Image Credit: NASA/ESA. Public Domain.

Moving westwards from M28, by 4 3/4 degrees, we arrive at the fabulous Lagoon Nebula, M8. At 4300 Light Years distance, the Lagoon appears as a titanic object in our skies. It is a degree and a half in length and over half a degree wide – roughly three full Moon’s width by a Moon’s width – comparable in area to the Orion Nebula M42/M43 complex, though not quite as bright. Still at +6 mag it is an easy object in large binoculars and small telescopes, though at a maximum of 14 1⁄2 degrees above the horizon at its highest for the UK, it can be a tricky object for those without a clear southern horizon. The Lagoon is so prominent, it was first cataloged by the telescopic observer Giovanni Battista Hodierna in, or slightly before, 1654. It was also noted by English Astronomer Royal John Flamstead around 1680 and French Astronomers de Cheseaux and Le Gentil in 1747 and 1748 respectively. Messier cataloged the Lagoon in 1764, noting both the cluster that lies within the nebula and the nebulosity.

The Lagoon is home to numerous young stars and the Hourglass section of its interior is actively observed to be in the process of stellar formation. It is these stars that cause the nebula to glow its distinctive pink colour, which makes the Lagoon another very attractive target for astrophotographers.

Astrophotograph showing the Trifid Nebula and the Lagoon Nebula in Sagittarius.

The Trifid Nebula and The Lagoon Nebula. Image Credit: Ljubinko Jovanovic. Creative Commons.

1 1⁄2 degrees north of the Lagoon lies the magnificent Trifid Nebula, or M20. This is one of the best deep sky objects in the sky to observe and can be easily found in binoculars and telescopes. At +6.30 mag and half a degree across, the Trifid is an impressive sight. Progressively larger instruments will show the dark lanes that trisect this object and a UHC filter will also help isolate the lanes and enhance the brighter HII regions. It was the trisecting pattern of dark material that gave rise to the Trifid’s popular name. John Herschel was the first to describe it as such and the name stuck, though it was first discovered by the French observer Le Gentil in 1750 and later cataloged by Charles Messier, if he rediscovered it on June 5th 1764. Located around 5000 Light Years from us, the Trifid is the stellar nursery for a number of stars which also illuminate the bright blue reflection nebula to the North of the object’s edge. The beautiful range of colours in this target and the starkness of the dark lanes gives M20 an amazing three-dimensionality and makes it a perennial subject for astrophotography. As M20 and M8 lie so close together in the sky, they make for a fantastic pairing in wider field images. It is thought that the Trifid and the Lagoon are both constituent parts of a much larger molecular cloud, much as the separate components of the Orion Nebula are, though the Trifid lies a little further from us and is potentially somewhat younger - current estimates put it at around 300,000 years old, which would make it around 10 light years across.

2/3 of a degree to the NE of the Trifid, sits the open cluster M21. At +5.90 mag and 14 arc minutes across, M21 is fairly prominent and can normally be found in the same binocular field as its neighbour. Containing upwards of 50 stars, this cluster is thought to lie around 4000 light years away - somewhat closer than its neighbour and due to the spectral signature of its stars is assumed to be around 4-5 million years old.

Just under 4 degrees to the NW of M21 sits yet another Messier object - the lovely open cluster M23. A little brighter than M21, M23 is +5.5 mag and is twice the diameter at 29 arc minutes wide and a glorious sight in telescopes and binoculars. This cluster is practically the same width in the sky as the Full Moon and its brightest members form a fan shape in its central region. M23 lies around 2000 light years from our solar system and is thought to be around 20 light years in diameter. It is a little older than its neighbour as spectral data reveals the oldest of its stars to be around 300 million years of age.

Drifting eastwards, about equidistant from M23 on the other side of the +3.8 mag star Polis, Mu Sagittarii, we come to yet another of Sagittarius’ fine clusters, M25. Discovered by de Cheseaux in 1746, M25 was independently rediscovered by Messier in 1764. It is bright at +4.59 mag and an easy target for those with binoculars and small telescopes. At 29 arc minutes diameter, it is the same dimensions in the sky as M23, though a little more concentrated in brightness. There are under 40 easily observable stars in M25, though there are many more - up to 600 - in the cluster as a whole. Some of the brighter members of the cluster form a star chain that appears to be akin to the letter W on its side - or maybe more pertinently, the Sigma sign. This can be seen easily through telescopes at moderate power. As M25 contains G class giant stars, this suggests that the cluster is around the 90 million year old mark and the cluster is thought to lie a similar distance from us as M23 - around 2000 light years.

Crossing back westwards from M25, back in the direction of Polis, we come to another Messier target - M24. This object is often known as the Sagittarius Star Cloud, as it represents one of the brightest parts of the Milky Way in this area of the sky. Describing M24 as “a large nebula, containing many stars” Messier listed M24 with dimensions of 1.5 degrees across. Although a fainter cluster, NGC6603 is contained within these boundaries, it is clear from Messier’s description that this is not what he was cataloging. Easily seen in binoculars and wide field telescopes, M24 represents the truncated end of the Sagittarius-Carina Arm of our galaxy - the arm adjacent to the Orion-Cygnus Spur which our solar system sits in. A gap in the surrounding dust clouds frame this area and this void allows M24 to appear particularly bright from our location - though this is simply a line of sight effect. Binoculars reveal a huge number of stars within this area - over 1000 visible in such a small area. Although strictly speaking not a nebula or a star cluster, M24 is a very interesting area of sky to examine and is well worth tracking down.

Found 1 1/3 degrees north of the Sagittarius Star Cloud is M18 - though at +7 mag and loose conformation, it is one of the less exciting of the Messier list in this part of the sky. This open cluster contains around 30 visible members spread over a 5 arc minute field and is thought to be around 4-5000 light years away. A comparatively young cluster at around 30 million years of age, M18 is about 17 light years in diameter. Long duration astrophotography reveals faint nebulosity surrounding this cluster - whether this is the remnants of the nebula the cluster formed from or material it is encountering in its way around the galaxy is still the matter for debate.

Lying 1 1/4 degrees to the N of M18 is the final object of note we shall be covering in Sagittarius - and what a way to end. The Omega Nebula, otherwise known as the Swan, Lobster or Horseshoe, take your pick, or more properly, M17, is a bright nebula of +6 magnitude and a healthy 46 x 37 arc minutes in size. This object is capable of being resolved by the naked eye under ideal conditions, rarely from the UK due to atmospherics, but is easily picked up in binoculars and marvellous in telescopes of all sizes. Discovered by de Cheseaux in early 1746, Messier discovered it independently in 1764.

Image of M17, the Omega Nebula, showing bright emission nebulosity and dark dust structures.

M17 - The Omega Nebula. Image credit: ESO, Creative Commons.

While not as extensive as the Orion Nebula, M42, M17 has a brightly condensed core and as such is arguably the second most prominent emission nebula in the sky. A telescope will reveal the looped structure of the gas clouds against which are silhouetted dark clouds of material, which causes the distinctly swan like shape. The looped area of the “neck” of the Swan is what gave rise to the Omega and Horseshoe nicknames - as this section does resemble the Greek letter, or indeed the shoe of a horse. The Lobster nickname comes from the tail-like section of the nebula - the opposing end to the swan’s neck - and the red-pink colour of the nebula revealed in long duration astrophotography. The glowing gas clouds of this nebula are powered by newly-formed stars hiding in its interior. These massive stars can’t be seen optically, but studies of the nebula at other wavelengths have revealed their presence. These stars are big and extremely luminous - it is estimated they are anything up to 30 times the mass of the Sun and 6 times hotter. It is estimated there is enough material left in the Omega Nebula to form up to 800 stars the mass of the Sun - a much higher number than that the Orion Nebula is capable of producing. M17 is thought to lie around 5-6000 light years from us.

Leaving Sagittarius, we briefly cross over its northern border into the constellation of Serpens Cauda - the tail of Serpens. Just under 2 1/2 degrees to the north of M17 sits a magnificent 35 x 28 arc minute target: this object is the +6.40 mag star cluster and nebula, M16 – otherwise known as the Eagle Nebula. Made famous by the famous “Pillars of Creation” Hubble Space Telescope picture, this object is well seen in all kinds of telescope, but the larger the instrument, naturally, the more you can see of it! The star cluster formed from the surrounding nebulosity, which can be glimpsed in a sub-6-inch telescope. An instrument of the class of a 12-inch+ Dobsonian will be needed to see the “Pillars” and OIII or UHC-type filter will help considerably with this. Photographically, the Eagle Nebula is a fantastic subject. Amateur CCD images of the nebula may lack the resolution of the Hubble image, but can reveal a surprising amount of equivalent detail.

Image of the Eagle Nebula showing star-forming pillars and surrounding emission nebulosity.

The Eagle Nebula. Image Credit: ESO. Creative Commons.

The Eagle was discovered by de Cheseaux in 1745 or 46 - though he simply listed the star cluster as the point of focus. Messier, independently recovering it nearly 20 years later in 1764, not only mentions the star cluster, but also the impression that the stars within it were “enmeshed in a faint glow” - a clear sign that nebulosity was evident to him in his observations. Certainly the nebulous regions of M16 start to be visible in a telescope of around 8-inches of aperture, but as previously mentioned, 12-inches of aperture will be needed to start making out structure within the nebula itself.

Modern astrometry puts the Eagle at about 7000 light years from our neck of the cosmic woods - similar in distance to the aforementioned Omega Nebula. Some theorists postulate that the two objects may be linked by the same molecular cloud and form two parts of a constituent whole. Certainly, there can be little doubt that they both lie in the same part of our galaxy - the Sagittarius-Carina spiral arm, but are they more closely related?

The age of the stars in the cluster seem to suggest that M16’s stellar population itself is around 5.5 million years old. Some astronomers have pointed out that while the “Pillars of Creation” area of the Eagle Nebula is prominent from our perspective today, that stellar compression by cosmic wind and the sheer luminance of the newly formed stars has probably already eroded these completely - in 7000 years-or-so, we’ll find out if this is actually true!