The Sun is at its highest as sunspots hit 11-year low
For would-be star and planet observers, June is probably not the month to take up astronomy as a hobby, at least from the latitude of Scotland. The summer solstice at 22:44 BST on the 20th marks the culmination of the Sun’s climb northwards in the sky, meaning that our days are at their longest and our nights are brief and mired throughout by a twilight that hides the fainter stars. Indeed, from northern Scotland it may be a challenge to spot even the brighter stars depicted on our star maps.
In many years, the Sun itself provides some compensation for observers fascinated by the changing patterns of sunspots on its dazzling surface. It is unfortunate, though, that 2020 is coinciding with the minimum in the Sun’s roughly 11-years cycle of sunspot activity so that days and weeks are passing with little to view beyond a pristine, and relatively boring, solar disk. On the other hand, the first spots of a new cycle of activity, the 25th since regular records started in the mid-18th century, are being sighted and their numbers are expected to ramp up towards the next sunspot maximum, currently forecast for July 2025. We just need to be patient.
I must stress that direct observation of the Sun through binoculars or a telescope, even for a moment, is hazardous to our eyes and can result in blindness. Projection of the Sun’s light through a small telescope or binoculars allows the solar disk to be viewed on a white card, although many people are turning to inexpensive but certified sheets of “solar filters” which can be acquired online and allow safe solar observation provided their instructions are followed carefully.
Edinburgh’s sunrise/sunset times change from 04:35/21:48 BST on the 1st, to 04:26/22:03 at the solstice on the 20th, and to 04:31/22:02 on the 30th.
The Sun’s shallow dip below our northern horizon overnight does mean that we are enjoying the optimum period for viewing noctilucent clouds, or NLCS. These “night shining” clouds are the highest of the Earth’s clouds and occur at altitudes of between 76 and 85 km where they are composed of tiny ice crystals forming during the summer months around particles of dust, some of which may be meteoric in origin. High enough to be lit by the Sun long after run-of-the-mill lower level clouds are in darkness, NLCS are usually bluish and often cluster as wispy cirrus-like structures low down in our northern sky between one hour after sunset and one hour before sunrise.
The bright star Capella in Auriga, which moves from low in the north-north-west at nightfall to the north-northeast before dawn, serves as a handy guide to where they are most likely to appear. Outstanding displays can reach much higher, and they have even been glimpsed from as far south as southern Europe.
The first NLC of 2020 was spotted unusually early on 17 May by Nasa’s AIM satellite, which was launched to study them 13 years ago. With luck, they will be an occasional highlight of our nights until mid-august.
The southern half of the Moon passes through the northern periphery of the
Earth’s shadow at full moon on the 5th, but the resultant penumbral lunar eclipse results in very little dimming and, in any case, is almost over by the times of moonrise and sunset for Edinburgh.
The Moon’s last quarter comes on the 13th while new moon on the 21st brings an annular solar eclipse when the Moon is too distant to hide the Sun’s disk. Instead, a dazzling ring of sunlight is seen along a narrow track that runs from East Africa to China and beyond. No eclipse at all is visible from Britain. First quarter occurs on the 28th. The gibbous Moon stands above Spica in Virgo on the 1st and moves onwards to lie above Antares in Scorpius on the 4th as the red supergiant twinkles barely 8° above Edinburgh’s southern horizon at our map times.
Those maps plot Jupiter and Saturn low down in the southeast as they climb to lie almost 13° high towards the south before dawn. Jupiter, brighter than any star at magnitude -2.6 to -2.7, lies 5° to the right of Saturn, magnitude 0.4 to 0.2.
When the Moon sits below Saturn on the morning of the 9th, Saturn’s rings span 41 arcseconds around its 18 arcseconds disk, while the cloudbanded
The maps show the sky at 01:00 BST on the 1st, midnight on the 16th and 23:00 on the 30th
disk of Jupiter is 46 arcseconds across.
A third morning planet, though of a very different nature, is Mars, which rises at Edinburgh’s eastern horizon at 02:23 BST on the 1st and by 00:55 on the 30th after it speeds 19° eastwards (to the left) from Aquarius to Pisces. Improving from magnitude 0.0 to -0.5, it is becoming more obvious in the southeast before dawn and is 10 arcseconds in diameter when it lies above the last quarter Moon on the 13th. Venus has dominated our evening sky and these notes over recent months but is now lost in the Sun’s glare as it moves to pass just north of the Sun, and 43 million km from the Earth, at inferior conjunction on the 3rd. Thereafter it makes a slow reappearance in our predawn sky, its altitude in the northeast at sunrise being only 5° on the 19th, when it blazes at magnitude -4.3 and lies 2.4° left of the very slender waning Moon. Venus met Mercury on 22 April and Mercury is still visible low down in the northwest after sunset. It shines at magnitude 0.6 and stands furthest from the Sun, 24°, on the 4th but may be lost a week later as it fades and sinks lower.