Welcome to the June night sky. This is the month of the summer solstice in the northern hemisphere. It occurs when the Sun reaches its highest point in the daylight sky and therefore we have the longest day and shortest night of the year.
The movement of the Sun across the heavens is reassuringly predictable and constant, a fact well understood by people of prehistoric times with their stone age constructions often aligned with the points on the horizon that coincided with the rising and setting of the solar and lunar discs. This year the summer solstice is on Monday the 20th and no doubt many will arrive at Stonehenge on a possibly grey Monday morning hoping to see the sunrise.
The Sun goes through this cycle every year, and the Moon also has its own cycle of highs and lows in the sky. The lunar cycle is much more complex and takes 18.6 years to complete; a fact also known by prehistoric people and used by them to predict eclipses. The stone circle at Almendres in southern Portugal is older than Stonehenge and has multiple alignments to the Sun and the Moon.
The ringed planet Saturn comes to opposition on June 3 but it will be rather low in the southern sky just to the upper left of the bright star Antares, in the constellation of Scorpius.
The red planet Mars that came to opposition last month is just to the upper right of this same star. As these two planets are low in the sky, they will be difficult to view through a telescope as our atmosphere will blur their images somewhat.
In June, we have a number of minor meteor showers, the best of them is the June Lyrids. This shower is active and visible during June 10-21.
We also have a comet possibly visible with binoculars – it’s called X1 panSTARRS and its orbit means it will pass below the constellation of Scorpius, moving towards the west and staying just above the southern horizon during the second half of the month.
This comet may not be seen from northern Europe as it will be too far to the south in the night sky this month, but as our latitude in Portugal is around 15 degrees further south, the comet will be 15 degrees higher up in the southern sky.
This difference in latitude has other effects as, during the year, the Sun rises and sets at more of a steeper angle than further north, so the length of twilight is notably shorter and this gives us a darker night sky in summer.
The moon is new on the 5th, first quarter on the 12th, full on the 20th, and last quarter on June 27.
By Clive Jackson
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Clive Jackson is the Director of the Camera Obscura (next to the Castle in Tavira), specialising in education and public outreach.
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To see the June Sky Map click on the pdf link below