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Sky Guide for June
Monthly Sky Guide for June
June is significant for Astronomers in may ways. For those of us who find ourselves in the Northern Hemisphere, June is the lightest part of the year. This owes itself to the Summer Solstice falling on the 21st June for the Northern Hemisphere. At this point, the Sun reaches the most northerly point in the Ecliptic and its highest separation from the horizon at Midday. Of course, for every action, there's an equal and opposite reaction - while we Northerners bask in the glory of Midsummer, those in the Southern Hemisphere are in the grip of Midwinter. The cause of these extremes - and all our seasonal weather on Earth - is our planets' rotational tilt (around 23.5 degrees from "vertical") in comparison to the plane of our orbital path around the Sun. During the Summer time, the leading hemisphere is pointed towards the Sun, thus receiving more light to warm up the land and sea. Days are subsequently longer and nights are shorter, the further towards the pole you find yourself. In Midsummer, those above the Arctic Circle experience 24 hour daylight. Of course, the opposite is true for all of this if you find yourself in the trailing hemisphere.
The Solar System
The Moon starts June in Sagittarius, low in the southern ecliptic from a northern hemispherical perspective, at just past Full. Rising early in the morning on the 1st, the Moon sits around 3/4 of a degree north of Saturn. Being so close to Full Moon, naturally, this is not the best time for deep sky observations, or imaging faint objects without significantly narrowband filtration. The Moon reaches Last Quarter on the 6th, while residing in Aquarius.
The Moon reaches New as it joins the Sun in Taurus on the 13th, after which it becomes an evening target. The evening of the 16th, it is possible to pick out the very slim Crescent Moon alongside Venus, just after sundown, with the two bodies separated by 5 degrees (when viewed from Europe), close to the Beehive cluster in Cancer.
The Moon reaches First Quarter in Virgo on the 20th and can be found alongside Jupiter in Libra the evening of the 23rd, with the Moon 3 1/4 degrees north of the prominent planet.
The Moon becomes Full in the early morning of the 28th, while in Sagittarius. Again, as was the case in early June, this is not the ideal time for deep sky observations and imaging. This is the furthest south within the ecliptic the Moon will appear as Full for the entirety of the year. Subsequently, it will sit very low in the sky from a northern hemispherical perspective, with atmospheric lensing enhancing its apparent girth.
The end of June finds the 17 day old Waning Gibbous Moon in Capricornus, around 4 degrees north of the bright pre-opposition Mars - the two targets rising just before midnight on the 30th.
At the month's beginning, Mercury is pretty much at maximum observable brightness at -1.6 mag (it gets brighter still when in extreme proximity to the Sun), though its separation from the Sun is under 7 degrees. Standing around two degrees high at sunrise (from latitude 51 degrees N), the planet will be extremely difficult from temperate northern hemisphere locations, though those in the equatorial regions of Earth should still be just able to observe it - but not for long.
Mercury reaches superior conjunction in the 6th June, passing north of the Sun in Taurus. By this point it will be unobservable and will remain so for a while as it climbs into the evening side of the sky.
By mid-month the -1.1 mag Mercury stands around 6 degrees high at sunset (from latitude 51 degrees N) in the constellation of Gemini. Mercury's separated from the Sun by just under 11 3/4 degrees at this point in time.
Mercury ends June at -0.1 mag, presenting a 61% illuminated, 6.6 arc second diameter disk. It stands a little under 11 degrees high at sundown (from latitude 51 degrees N), and is thus well-placed for observation from northern parts - though those in the equatorial parts of the planet will see it better, as it is now separated from the Sun by 23 1/2 degrees.
At the beginning of the month, Venus can be found in Gemini, at -4.0 mag and 13 arc seconds angular diameter. The planet is presenting an 80% illumination, which will continue to diminish as it grows closer to Earth on its interior orbit. Venus stands 22 degrees high above the horizon in the west at sunset (from latitude 51 degrees N) on the 1st, some 34 1/2 degrees from the Sun itself.
As Venus has passed over the highest northern point in the ecliptic, it is slowly losing altitude for those of us in the northern hemisphere - though it is still some way off greatest eastern elongation from the Sun (this occurs in mid-August). Concurrently, it is gaining altitude for those in the southern hemisphere and equatorial regions of the planet. It is also increasing in angular size and brightness as it draws closer to Earth - though again, this is a gradual process.
By mid-month, Venus has crossed over the border into Cancer and while it hasn't increased in brightness, it has swelled somewhat to 14.3 arc seconds diameter and its phase has decreased to 75%. It now stands 20 1/2 degrees high, almost due west at sunset (from latitude 51 degrees N).
By late June, Venus has crossed into Leo and increased brightness to -4.1 mag. Presenting a 15.7 arc second, 70% illuminated disk, the planet stands 18 1/4 degrees high in the west at sunset.
At the beginning of the month Mars can be found in Capricornus, shining at a very healthy -1.2 mag and is now 15.3 arc seconds across. The planet now sits just under 17 degrees high in the south as the Sun rises (from latitude 51 degrees N). Mars is now a serious target for observation in any telescope and will display continental-sized surface features in practically any telescope. The use of filters, particularly the #23A Light Red filter, will help isolate these darker parts of the Martian disk. An #82a Light Blue will also help Mars' polar caps stand out. This filter will definitely be of use as during this particular Martian apparition, Mars' smaller southern polar cap will be turned towards us. This is more difficult to spot than the larger northern cap, which was turned towards us in the first few months of 2018, and the adjacent Hellas basin, which often fills with mist and clouds, can often appear very bright and is easily mistaken for the southern polar cap. Observations at different frequencies bring certain features to the fore and make their identification easier and more precise.
By mid-month, Mars is brighter still, having increased its brightness by half a magnitude to -1.7. The planet is now 17.8 arc seconds diameter and stands at 16 1/2 degrees high in the south at sunrise (from latitude 51 degrees N).
At the end of June, Mars is still found in Capricornus and is now -2.1 mag brightness - just a little less brilliant than Jupiter - and displays a 20.7 arc second disk. Mars rises at a little after 11.19 pm local time (from latitude 51 degrees N) and now transits at 3.20am the following morning. We are still a few weeks off opposition in July, but every opportunity should be taken to observe the Red Planet in the run-up to its best.
The beginning of the month finds Jupiter at -2.5 mag and 44.1 arc seconds across. The planet will stand 23 1/4 degrees high as it transits, which will occur just before 11.13am (BST, from 51 degrees N). Jupiter at a little past opposition will dominate the sky in Libra, rising in the early evening. This is a great time to observe the planet at a reasonable hour of the night. The run up to opposition always sees a planet not reach its highest point in the sky until the early morning. Post-opposition apparitions of planets sees them rising earlier and earlier, so the next couple of months are the "sweet spot" for Jovian observation and imaging in the evening. Naturally, Jupiter will continue to rise earlier as the year progresses, but this will be offset by the planet shrinking somewhat as we pull away from the opposition point.
Mid-June finds Jupiter having faded fractionally to -2.4 and now presenting a 43 arc second diameter disk. Jupiter rises at just before 5.30pm, transiting around 10.12pm (BST, from 51 degrees N), when the planet will be 23 2/3 degrees high in the south.
By the end of June, Jupiter is at -2.3 mag and 41.4 arc seconds across. The planet will stand just under 24 degrees high as it transits, which will occur at 9.10pm (BST, from 51 degrees N). Although Jupiter is rather low as seen from the northern hemisphere as Geof Lewis' recent picture below shows, there's plenty of detail still visible - especially from a high speed imaging perspective.
Late June finds Saturn at opposition, so now's the time to catch the ringed planet at its best. The beginning of June finds Saturn joined in Sagittarius by the waning gibbous Moon, just a little after Full. At this point, Saturn displays an 18.2 arc second diameter disk, and is +0.2 magnitude in brightness. The planet rises at a little before 11pm (BST) and transits at just before 3am, when attains an angular height in the sky of just under 16 1/3 degrees (from 51 degrees N).
Mid-month finds Saturn at +0.1 magnitude brightness and now displaying an 18.3 arc second diameter disk. The planet now rises and transits around an hour earlier than it did at the month's beginning.
Saturn reaches opposition on the 27th June, when it reaches +0.0 magnitude and attains its maximum diameter of 18.4 arc seconds for the year. Naturally, being so far south in the ecliptic, this opposition favours the southern hemisphere, but Saturn is always a rewarding target no matter where you observe it from. High speed imaging will help ride out seeing conditions for those of us in the northern hemisphere somewhat - synthesising much higher resolution images than would ever possibly be observed through a telescope, even in the most clement of atmospheric conditions. Equally viable, if you have the aperture of telescope to use successfully, would be the use of heavy filtration for visual observations - particularly the harsh Deep Red #29 filter. This attenuates the worst excesses of atmospheric jitter and can really make a difference when attempting to discern detail on the brighter planets when they are closer to the horizon. Wherever you find yourself in the world, the jewel-like Saturn should be number one on your observing list this month and for some time to follow.
Uranus and Neptune
Of the two outer gas giants, Neptune is better placed for morning observation in Aquarius than its neighbour Uranus, itself further east in the ecliptic and closer to the Sun in Aries. By the end of June, Neptune is approaching transit point in the south as the Sun rises. At +7.9 magnitude, you'll need a pair of reasonable binoculars, or better still a telescope to find the outer planet.
Uranus, at +5.8 magnitude in Aries rises about an hour and half before the Sun at the end of June, so is still a real challenge to observe in the morning twilight through June, though significantly brighter than Neptune is less difficult to find in binoculars and telescopes.
Comet PanSTARRS C/2016 M1, is the only reasonably bright comet that it may be relatively easy to observe from some parts of the world, as it continues its journey south through Sagittarius. Although the predicted brightness of the comet is difficult to predict, it could be as high as the 7th magnitude, but is more likely to be hovering between the 8th and 9th magnitude as it heads Sunward. Sadly, for observers in higher northern latitudes, it is sinking towards the southern horizon fast and the presence of the bright gibbous Moon in the same area of sky at the beginning of the month won’t help observations at all.
By the 8th of June, the old crescent Moon will be far enough separated from the area of sky the comet is sitting in to make reasonable observations of it, though atmospheric extinction for higher northern latitude observers will have a negative part to play. On the morning of the 8th, C/2016 M1 sits just 1/2 a degree to the NW of Ascella, Zeta Sagittarii - the second magnitude star marking the bottom of the well known “Teapot” feature in Sagittarius. This will make finding the comet fairly simple for those with reasonable skies.
Beyond this point in time observations from the northern hemisphere move from difficult, to nigh on impossible, as the comet’s path moves it closer to the horizon. Once mid-June is upon us, the comet is the preserve of those in the southern or equatorial regions of the planet.
Comet 21P/Giacobini-Zinner should be brightening up in the northern celestial hemisphere and should be observable - certainly in telescopes and larger binoculars. This regularly returning (6.5 year orbital cycle) comet will be heading northward during June through Cygnus and should be fairly easy to find. The comet will brighten rapidly in August and September, as this apparition passes very close to Earth (0.39 au), so should be a low naked eye object then.
Noctilucent Clouds are often seen in June - their bright gossamer-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. Whatever their origins, now is the best time to see them from Northern latitudes. Interestingly, whilst Noctilucent Clouds have been observed in the Southern Hemisphere, their incidence appears much, much less than their Northern Hemispherical counterparts. Whatever their origins, now is most definitely the right time to witness their ghostly displays.
Deep Sky Delights
in the East of Hydra, Corvus and the South of Virgo.
We covered Coma Berenices and the Bowl of Virgo in last month's sky guide. This month we will turn our gaze to the southern part of Virgo and the constellations that sit yet further south below it: the tail of Hydra, the Water Snake and Corvus the Crow and Crater the Cup, which sit atop his back.
The first major object south of the Bowl of Virgo is the galaxy NGC4697, which is a brighter elliptical galaxy, discovered by William Herschel in 1784. This galaxy is fairly easy in small telescopes, as is its neighbour NGC4699, an attractive but compact spiral, which lies just under 3 degrees due South. At +9.19 mag NGC4697 is not especially bright, but is fairly easy to find, lying at the bottom of an imaginary equatorial triangle formed by the stars Porima, Gamma Virginis, a notable binary and good test of optics, and its neighbour Theta Virgis, also a double star. Tracing a line between the two stars, once you come to about half way, head South by just over 3 degrees. Here you will find NGC4697. This galaxy is thought to lie some 40 million light years away from us.
Virgo has many splendours, but a particularly popular one is M104, the Sombrero Galaxy, which can be found around 6 degrees to the south of NGC4697. The Sombrero was discovered in 1767 by Pierre Machain and though noted by Messier in an addendum to his original list, had to wait until Camille Flammarion rediscovered it in Messier's original notes in the early 1920s for it to be officially added as a Messier object. William Herschel made an independent discovery of it in 1784 and remarked upon the appearance of a "dark stratum" in the object. We now know this to be a prominent dust lane which rings the outer spiral structure of the Sombrero and gives it its distinctive - and apt -nickname.
The Sombrero is bright for a galaxy at + 8 mag and a decent size, (though hardly over-large) at 8.6 x 4.2 arc minutes in dimensions. It can be found in telescopes and binoculars of all sizes, though contrary to what is stated in many publications (which tend to overstate the size of telescope required), a good quality 4-inch refractor and a dark observing site and decent dark adaption will be needed to see its dust lane. Admittedly, the lane is much easier with a reflector of 8-10 inches in aperture, which will also resolve the true shape of the Sombrero better, but this should not put off observer with smaller instruments from attempting to spot it. Once found, M104 will not be forgotten in a hurry, it is a lovely object. M104 is even more spectacular when imaged, though from UK locations astrophotography of this target has to be timed carefully, as it is only at a reasonable height from the horizon for a limited period.
M104 is thought to lie around 30 million light years away and calculations show that although it is around half the diameter (50,000 light years) of our own Milky Way Galaxy, it is considerably more luminous and has many more than our own galaxies number of attendant Globular Clusters - 1200 to 2000 compared to the Milky Way's estimated 160 - more in line with a much larger Spherical Galaxy like the nearby Virgo A. M104 is also thought to be home to a supermassive black hole and the first object to have its redshift measured, which proved that it was clearly not a part of the Milky Way in 1912.
Leaving Virgo on a high note, we head further South into Hydra and its attendant constellations. Hydra is the largest constellation in the sky: a huge serpentine arrangement of stars in the southern celestial hemisphere, reaching all the way from its northerly borders with Cancer and Monoceros to the constellations of Libra, Lupus and Centaurus at is southerly tip. From a dark location, the Water Snake and its attendant and mythologically associated constellations of Corvus and Crater are easy enough to spot, but these constellations are much more of a challenge from light polluted areas.
In ancient Greek myth, Corvus the Crow was distracted from his assignment of delivering water in Crater the Cup to the god Apollo. He was waylaid waiting around for figs to ripen and forgot all about Apollo. Upon realising his mistake, he flew quickly to the god, picking up the unfortunate Hydra on the way, claiming that the Water Snake had stolen Crater from him and thus caused the delay. Apollo saw through this fabrication and cast all three into the heavens, charging the unfortunate Hydra with the task of guarding Crater forever, denying Corvus water in perpetuity. A little harsh maybe, but small fry compared to some of the punishments meted out by the gods in classical mythology.
The rather faint constellation of Crater the Cup sits atop the Water Snake's back and is home to many galaxies, though sadly none of these is brighter than +11 mag, apart from the reasonably prominent spiral NGC 3887, which at +10.60 mag is observable in larger telescopes of 8-inches aperture and above and a worthy photographic target. NGC 3887 was discovered by Sir William Herschel in 1785 and displays itself as a compact, almost face-on spiral which displays itself as a brighter core with its spiral arms shown a surrounding halo of misty light. The large amount of other galaxies in Crater are the preserve of these with yet larger instruments and dark skies.
Neighbouring Corvus the Crow is a little brighter as a group of stars, which are formed into in a noticeable quadrilateral arrangement. Arab astronomers identified Corvus as a tent, Chinese astronomers as a Chariot and others as a sail. In a similar situation to neighbouring Crater, Corvus contains many galaxies - the vast majority of these being overspill from the nearby Virgo cluster. However, most are, like Crater's quite faint. The brightest galaxial target is however spectacular in both telescopes and astrophotographs; NGCs 4038 and 4039 - the Antennae Galaxies.
Again, discovered by Herschel in 1785, these two spiral galaxies are the closest and most recent example of colliding galaxies in the whole sky. At 40-45 million light years distance, the Antennae really do look like their nickname, as the tidal interaction of the collision has sent out two huge, long arcs of stars in either direction - over 350,000 light years into deep space.
At +10.30 mag, the Antennae can be picked up in reasonable-size telescopes with little effort, with both galaxies displayed as adjoining ear-shaped objects. Larger instruments of 8-10-inches plies will show the beginnings of the more southerly arc of stars as a small spur-like point, sticking out from the "earlobe" of NGC 4039. However, it is in astrophotographs that the true nature of this amazing object is revealed. For those with suitable equipment, skies and location (remember this object is very far south for those in the UK) the Antennae is a a great subject for imaging.
Five degrees to the east and a little to the north of the Antennae, lies the compact but pretty planetary nebula NGC 4361. Common with many planetaries, it is not that bright - in this case + 11 mag - but NGC 4361 is compact (at 1.6 x 0.6 arc minutes), which makes it quite an easy target in a 6-8-inch scope. NGC 4361 forms the right angle point of a right angled triangle with Gienah Corvi (Gamma Corvus) and Algorab (Delta Corvi). From a dark site it will be easy to pick out from the background stars and has an uneven, almost rough appearance. Its central star is +13 mag. As with most planetaries, when it comes to visual observations, gains can be made by keeping magnification fairly high and using either OIII or UHC filters to help keep contrast with the background sky healthy.
The last two objects we turn our attention to this month are always challenging for observers in the northern hemisphere as they are located so far south. The first of these, the globular cluster M68, lies 15 degrees almost due south of the Sombrero, back inside Hydra. M68 is a true Messier object, it was discovered by Messier in 1780, though is often erroneously attributed to Mechain. M68 is not the brightest of globulars at +7.84 mag, though at 3 arc minutes diameter is almost as large as the prominent M13 in Hercules. Easily seen, once located, in most telescopes and binoculars, though M68 is naturally better resolved by larger instruments, which will show the shallow curve of dark lanes around the south of the cluster. M68 lies around 33,000 light years distance from us here on Earth.
Last, but by no means least though, we come to the marvellous galaxy M83 - a true showstopper of an object, though a real challenge for those in northerly climes, standing as it does just 13 degrees high at most from 51 degrees N. Observers in the Southern Hemisphere will see this wonderful target much better than those in the North, lying as it does on the border between Hydra and Centaurus. This barred spiral galaxy is bright at +7.5 mag and 12.9 x 11.5 arc minutes dimensions and is presented face on to us - displaying its beautiful structure in all its glory. As with all Deep Sky observation, the larger the telescope and the darker the site, the more an observer will see, but anyone will be able to see something of M83 with some form of optical aid. The elongated part of M83's central bar is the most prominent part of the galaxy and will be picked up easily in large binoculars. However, its expansive looping spiral arms, bisected by dark dust lanes are really the preserve of telescopic observation.
M83 lies a comparatively close at 15 million light years distance from us, as part of the extended Centaurus cluster of galaxies. It is comparable in size with the Milky Way, with a diameter of around 100,000 light years. M83 is active in star formation and contains a large amount of hot young blue stars and active Hydrogen star-forming nebulae. As active as M83 is in star formation it is also rich in terms of the demise of stars: M83 previously held the record for the largest amount of Supernovae observed in one galaxy, though this has recently been surpassed by NGC 6946 and its count has also been equalled by M61.
Unsurprisingly, M83 presents itself exceptionally well in imaging terms, but it is really the preserve of astrophotographers considerably further south than those in the UK and Northern Europe and the Northern parts of America or Asia. Readers in the Southern Hemisphere are encouraged to make the most of M83 for both visual and astrophotgraphic terms - it's a beauty!
Special Thanks to Kerin Smith (Author)