June brings with it the Summer Solstice - the longest day and shortest night of the year. This year the solstice falls on 21st June and this is the point where the Sun reaches its most northerly point in the ecliptic. With Solar activity beginning to pick up again after quite an extended solar minimum, this time of year also represents the best for making safe observations of our parent star. White light filters (including Herschel Wedges) or Hydrogen Alpha or Calcium-K line telescopes and blocking filters are to be recommended for this. White light filters will show the user sunspots and some surface granulation (depending on the instrument used and sky conditions), whereas Hydrogen Alpha systems are able to show the amazing features of the solar atmosphere: prominences, flares and ejection events.
Naturally, for every reaction, there is an equal and opposite one - during June, the Southern Hemisphere experiences its Winter Solstice. One we have passed the 21st, the nights for those of us in the Northern Hemisphere begin to get longer, as do the days in the Southern Hemisphere.
This has noticeable effects on the quality of darkness for those in temperate Northern latitudes, as during this point of the year, the Sun, even at the deepest point of the night is not so far below the horizon. For those in the Northern Europe and the Northern parts of the USA and Canada and Asia, this can mean permanent Astronomical Twilight for a while around the Summer Solstice.
From the 27th of May to 15th July 2022, there is a state of permanent Astronomical Twilight for those in latitudes around 50.5 degrees N, which means that the Sun is less than 18 degrees below the horizon all night long. This means that the skies are never truly dark and that objects around or below the 6th magnitude are unable to be distinguished with the naked eye (technically, +6.5 mag is generally seen as the limit of human eyesight, though this does vary from individual to individual). This obviously has knock-on effects for deep sky observation and astrophotography. The further north one observes from, the longer this period of permanent Astronomical Twilight persists: in Manchester UK (latitude 53.5 degrees N) this extends from mid-May to the end of July; in Edinburgh (just shy of 56 degrees N) the period is yet longer, from early May to the end of the first week of August. Do bear in mind, if you find yourself in latitudes similar to Reykjavik, Iceland (64 degrees N) Astronomical Twilight persists from early April to the beginning of September . North of the Arctic Circle, the Sun will not set at all around the Solstice, whereas south of the Antarctic Circle, the Sun won’t rise at all during this period.
No matter where you find yourself, as ever, there’s plenty to see in the skies above us this month.
The Earth’s natural satellite finds itself in Gemini at the beginning of June. At a small 4.9% illuminated phase, the Moon will be visible in the evening sky, after sunset, for a brief window, for those with a clear westerly horizon.
Through the next week the Moon climbs through Gemini, into the neighbouring zodiacal constellations of Cancer and Leo, where reaches First Quarter stage on June 7th. We are now past the region of the year where the Moon appears at its highest in the sky, during its evening crescent phase, for Northern Hemisphere observers - the so-called high Spring Crescent phases – so does not reach quite the extreme heights in the sky, as it has done in preceding months. However, the Moon still reaches a respectable plus 40° plus in altitude (from 51° N) at sunset on the evening of the 7th.
The Moon takes the next three days to cross the large expanse of Virgo and then moves on into Libra and Scorpius and the non-zodiacal Ophiuchus and Sagittarius, where it reaches Full on the 14th. This Full Moon will be one of the so-called ‘SuperMoons‘ (more correctly known as a Perigee-Syzygy event), which occur when the fully-illuminated Moon coincides with its closest approach to Earth, within its slightly less than circular orbit. The Moon does appear to be slightly bigger during an event like this and this will be compounded further by atmospheric lensing, when viewed from the Northern Hemisphere, with it sitting so low in the southern reaches of the ecliptic. While there is no great scientific significance to a ‘SuperMoon’ event, it has captured public imagination. However, it’s worth pointing out that Full Moon is one of the most potential disappointing times to view the lunar surface in a telescope, with very little shadow relief available.
With the Supermoon out of the way, our natural satellite continues its journey through Sagittarius and into neighbouring Capricornus, where it can be found a little to the south of Saturn on the evenings of June 18th.
Last Quarter phase is reached on June 21, when the Moon can be found in the southern part of Pisces, joining the bright Jupiter and the not-quite-so-prominent Mars in the same constellation. The morning of the 23rd finds the Moon and Mars drawing quite close to each other - separated by just over 5 degrees. A couple of days later and the slim 13.5% illuminated waning Crescent Moon will be separated from the faint Uranus by just over 3 degrees - though the glare of the dawn and the ever-present lack of astronomical dawn for those in higher latitudes will make this a very challenging event to observe.
Less challenging will be the Moon and the ever-dazzling Venus’ conjunction, which occurs on the morning of the 26th. Though by this time the Moon will be a very slim 7% illuminated phase. The two bodies will be separated by just two degrees and will form a beautiful pairing just below the Pleiades in Taurus. The following morning of the 27th will find the 3% illuminated Moon separated from Mercury by just over three degrees.
The Moon alongside Venus, sunrise, 26th June. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
The Moon becomes New again on June 29, when it meets the Sun in Gemini. This neatly “bookends” the month as far as the Moon is concerned and it is to be noted that the beginning and end of the month will best-suit deep sky observers. Though again, it is worth warning that at this time, the lack of true astronomical darkness in higher northern latitudes will also have a part to play in the quality of deep sky observing possible.
The Waxing Gibbous Moon imaged by Malcolm Porter, using an Explore Scientific David H Levy Comet Hunter 152mm f/4.8 Maksutov-Newtonian and a Canon Ra (ISO 800, 1/2000th second). Image used with kind permission.
Our Solar System’s smallest planet, Mercury, begins June in a less than ideal position for observation, in the morning sky. Emerging from May’s Inferior Conjunction, Mercury is drawing away from the Sun, form our perspective here on Earth, but it is still very poorly illuminated at the beginning of the month, making it impossible to observe in the glare of the dawn sky.
By the middle of June, the situation as far as Mercury is concerned has improved significantly. On June 15 at sunrise (from 51° north), we find mercury at +0.7 magnitude, sitting at a little over 7° high in the sky as the Sun rises. Mercury reaches maximum Western elongation on June 16th, but still appears to climb a little higher in the sky and increase its magnitude yet further, over the latter half of the month.
By the end of June, Mercury will be shining at -0.6 magnitude and standing a little above 8° elevation in the east as the Sun rises (from 51° north).
Mercury, sunrise, 16th June - greatest western elongation. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
Sitting in roughly the same area of sky (in the constellation of Aries) as Mercury, the much brighter Venus, shining at -4.0 magnitude on June 1 is very much easier to find. Standing at just over 11° high above the horizon (from 51° north), Venus is to be found almost due east at this time of year.
Venus is heading back sunwards in direction, after completing its furthest Western elongation in March. The planet is now moving away from us as time moves on, shrinking very slightly day-by-day, as it does. At the beginning of the month, Venus shows a 13.7 arc second diameter disc, illuminated by just under 78%. By the middle of June, Venus will display a 12.7 arc second diameter disk and while it will have increased its illuminated phase a little to just under 82%, this isn’t enough to prevent it dropping in brightness fractionally to -3.9 mag. In practical terms, this difference in brightness could only really be recorded astrometrically. To the visual observer, Venus would appear just as bright, though naturally enough, it’s apparent shrinkage would be more than evident in a telescope’s eyepiece.
As previously mentioned, Venus and the Moon come together in close conjunction on the morning of the 26th, which should make a pretty event to observe for the early riser.
The end of the month find Venus having shrunk a little further to 11.9 arc seconds diameter and is now a resident of Taurus, sitting just above the Hyades as the Sun rises on the morning of the 30th, at an altitude of around 14.5° (from 51° north). Now showing an 85.8% illuminated phase, the planet will remain steady in brightness at -3.9 magnitude.
Venus above the Hyades, sunrise, 30th June. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
The Red Planet continues to improve, slowly, but it’s still far from at its best.
On the 1st of June, Mars will be found right next to Jupiter, in southern Pisces, shining at +0.7 magnitude and showing a 6.4 arc second diameter disc. The two worlds are now separating after coming together for a very close conjunction in late May. The contrast between Mars and Jupiter could not be more apparent: while Jupiter is large, bright and prominent, Mars is more more modestly-seen - be this observed with the naked eye, or in the eyepiece.
By mid-month, Mars has brightened fractionally to +0.6 magnitude and is now displaying 6.8 arc second diameter disc.
Fast forwarding to the end of June, we find Mars still in Pisces, but now +0.5 mag and 7.2 arc seconds in diameter. We have still got some way to go until Martian Opposition later in the year, but as we can see, Mars is steadily improving - although it has a long way to go yet, in terms of improvement.
Mars and Jupiter, sunrise, 1st June. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
As previously reported, Jupiter and Mars are emerging from late May’s very close conjunction, so are to be found together in the southern reaches of Pisces, as the month begins.
On the first of the month, Jupiter displays an official magnitude of -2.3 and an apparent size of 37.4 arc seconds diameter. Although we are still some way off September’s Jovian Opposition, the trend is definitely upwards as far as Jupiter is concerned.
By mid-month, the planet has increased its diameter to just under 40 arc seconds. However, it remains steady in brightness at -2.3 mag. The planet will stand around 26° high in the south-east at dawn (from 51° north).
At the end of the month, Jupiter can be found as a brief resident of the non-zodiacal constellation of Cetus. At this time, the planet will be displaying a visual magnitude of -2.4 and an apparent size of just under 41 arc seconds.
There are a few interesting Jovian events to observe from Europe in June. Starting with a nice mutual Great Red Spot and Io/Io Shadow Transit on June 1st. This is followed by a GRS and Europa shadow transit, at just before dawn on the morning of the 3rd. There is another GRS and Io/Io shadow transit event on the morning of the 8th. Just before dawn on 18th June, there is an rare and interesting event, where Ganymede appears to transit the Great Red Spot itself - this will be well worth catching in a telescope, if you’re up early enough.
Jupiter with Ganymede transiting the Great Red Spot, dawn, 18th June. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
Saturn starts June a resident of Capricornus, at +0.8 magnitude displaying a 17.4 arc second diameter disk. Rising at a little before 2.30am (BST), Saturn is the furthest west in the ecliptic of all the major planets, so rises earliest. By the time the sun rises, it has attained a height of just under 22° (from 51° north).
During the first week of June, Saturn begins to go retrograde - changing position in relation to background stars not from west to east, but from east to west. This is a sure sign that the planet is gearing up for opposition. Retrograde motion is emphatically not the planet itself changing direction, but is caused by the foreshortening of sightlines by the Earth catching Saturn up on its faster interior orbit. Saturn will remain retrograde until late October.
By mid-month, Saturn will have brightened very slightly to +0.7 magnitude and now displays a 17.8 arc second diameter disk. It will rise at a little before 1.30am (BST) and transits in the south a little after dawn.
By the end of June, Saturn will have brightened up fractionally again to +0.6 mag and now displays an 18.2 orc second diameter disk. It will rise at a little before 12:30 am (BST) and transit as a little after 5 pm on the 30th.
While we still have some way to go before August’s Saturnian Opposition, Saturn, rising earliest of all the major planets is arguably our best proposition for planetary observation during June.
Saturn and Inner Moons, just before sunrise, 15th June. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.
Uranus and Neptune
Neither of the outer gas giants are particularly well-placed for observation this month.
Uranus, recently emerged from Superior Conjunction is poorly positioned in Aries for observation during June. Technically, it may be observable in a limited window, but lies a little too close to the Sun at present and doesn’t rise particularly highly before sunrise and will be very, very difficult to make out in the dawn sky. At + 5.8 mag, the glare of the approaching Sun will make contrast with the background sky an almost insurmountable problem.
Neptune, lying much for the west in the ecliptic in the constellation of Pisces, will rise earlier and will have attained a greater height above the horizon by sunrise. Nearby Jupiter will act as an indication of the area of sky in which Neptune can be found, but being fainter than Uranus, at +7.9 mag, will be a challenge to find and will definitely require powerful binoculars, or a telescope to do so.
It will really be a little later in the year before these two worlds be in a better position in the sky for more reliable regular observations.
Relative positions of Uranus and Neptune, sunrise, 15th June. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.