Russell Eberst's Sky View

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June 2020

During June the Sun reaches its furthest northern declination. This annual northern extreme (along with its southern equivalent) are known as the solstices, when the Sun is 23.5 degrees from the celestial equator over the tropic of Cancer or Capricorn respectively. There is one school of thought that the June 20 solstice marks the beginning of (northern) summer. A simpler system considers that summer consists of the months of June, July, and August, with other seasons consisting of consecutive groups of three months. This month the Sun never gets very far below the horizon at our high northern latitudes. In Iceland, Greenland and northern Scandinavia, the Sun remains visible all night. These areas are known as "lands of the midnight Sun". Even when the Sun does set, the twilight is likely to persist all night, making night observing very difficult. Only the brightest astronomical objects are likely to be available for observation. The Sun is, however, above the horizon for around 16 hours each day, so provides an alternative to night sky viewing. The activity on the Sun has been very low recently, but sunspots of a new solar cycle have been seen. These occur at higher solar latitudes than spots from he old cycle. If any flares or "coronal mass ejections" happen, then these can cause auroral displays in our northern latitudes.

During June a more likely visible phenomenon is noctilucent cloud. This month conditions are suitable for spotting noctilucent cloud from much of U.K. With the Sun not far below the northern horizon, these clouds can shine during the brief hours of the night. They display an unmistakable pearly blue hue, and their tenuous but complex structure often envelopes the bright stars of the constellation of Auriga the charioteer. Capella and Menkalinan should be checked on every clear night at this time of the year, to detect the presence of this unusual phenomenon. When the clouds are detected, the best method of recording the details is photography. Pictures should be taken every quarter-hour enabling easy comparison with similar photos taken at other locations. The clouds are the highest in the atmosphere, occurring at heights around 83 km. or 50 miles. They are thought to be caused by ice crystals that form around micrometeor dust located on the inner edge of our space environment.

Whilst looking for aurora or noctilucent cloud above your northern horizon, it is also possible that a bright comet may be spotted in Auriga. At the beginning of June, Comet Swan is located close to the star Capella. The name 'Swan' derives from the instrument that helped to discover it, the Solar Wind ANisotropies camera. Predicting the future brightness of comets is difficult (and in some cases impossible). Comet Swan seems likely to be visible to the unaided eye, were it not enveloped in the Sun's glare. Binoculars will be very helpful in picking out the head of the comet, and it could develop a long tail stretching upwards for a few degrees. The comet moves towards the Sun and by June 17-18 passes close to the star theta Aurigae, but by that time it is only 14° from the Sun. Observers are wary of raising their hopes of a bright comet, as Swan might well follow the example of Comet Atlas, and fizzle out prematurely.

Not far from the star theta Aurigae mentioned above, is the even brighter star beta Tauri. Also known as Elnath, it was designated in previous times as gamma Aurigae. You may have spotted it in the first half of May, close to the planet Venus. It once again gets our attention in late June, since it marks the radiant of a meteor shower, called the beta Taurids. This is a daylight shower not visible during night hours. The meteors can however be detected by radar or radio reflection methods. The famous Tunguska event of 1908 June 30, when a asteroid or comet broke up over Siberia, may well have been associated with this stream.

The eclipse season is with us - during June and early July there are a series of eclipses. The first of these occurs on June 5, when the Moon passes through the outskirts of the Earth's shadow. This is a penumbral eclipse, the Moon just misses the darker part of the shadow, resulting in only a dusky decrease in the Full Moon's brightness. The eclipse is finishing at moonrise in the U.K. Areas favoured for better views include Asia, Africa and Australia. This is the first of four penumbral eclipses in succession, the next one in July.

On June 21, hours after the solstice, the Sun undergoes an annular eclipse. The Moon's disc is only just too small to completely cover the Sun, on this occasion. Observers on the narrow track will see a thin ring of the Sun surrounding the silhouette of the Moon. The track crosses eastern Africa, Arabia, Pakistan, north India and China. Annularity is under a minute, causing rapid apparent changes.

Moon phases:

  • Full Moon: June 5
  • Last Quarter: June 13
  • New Moon June 21
  • First Quarter: June 28

Sky View Image

The maps show the sky at 01:00 BST on the 1st, midnight on the 16th and 23:00 on the 30th.