Russell Eberst's Sky View

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June 2018

Every June sees the Sun reach the most northerly point of its annual journey along the ecliptic. The north and south extremes are known as the solstices when the Sun is 23.5 degrees from the celestial equator over the tropic of Cancer or Capricorn respectively. Some authorities state that the June 21 (at 10.07 U.T.) 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. The Sun never gets very far below the horizon at higher northern latitudes. In Iceland, Greenland and northern Scandinavia, the Sun remains visible all night. These regions are referred to as "lands of the midnight Sun". With the Sun visible for a prolonged period, this is an ideal time to undertake observations of the solar surface. Of course, extreme care must be taken when dealing with such a high energy source as the Sun. Observing the solar disc by projection is a recommended method. However, there are alternatives using a filter. There are a number of telescopes specially designed for solar observations, but these can be quite expensive. So if you are considering making a regular study of the Sun's surface, one of these dedicated solar telescopes may be the correct purchase for you. They will show many solar details, not only the obvious sunspots. The number of sunspots visible is slowly decreasing from the maximum which occurred a few years ago. However, there are still a few seen at present and are a rewarding sight and show that the Sun is still far from becoming the quiet star that is expected at solar minimum.

During June, conditions are suitable for spotting noctilucent cloud from northern U.K. With the Sun not far below the northern horizon, the clouds are illuminated throughout the brief hours of the night. They display an unmistakable pearly blue hue, and their tenuous structure often surrounds 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. They have been measured to be at a height of 50 miles (80 km.) but it not entirely clear what triggers the occurrence of these ethereal clouds. Both eruptions from volcanoes and cometary dust have been suggested. More predictable are the planets, with Venus still ruling the western sky as the sky slowly dims during dusk. At magnitude -3.9, it far outshines the stars in the background, even the twins, Castor and Pollux. She passes these during the month and has now turned southwards. This means that it no longer increases its altitude from night to night, but moves further to the left on subsequent evenings. The crescent Moon can be seen to the left of the planet on June 16. Venus displays a gibbous phase when inspected under high magnification. In the southern sky, Jupiter is prominent in the constellation of Libra, the scales. It continues to move westwards (retrogrades), with this motion most obvious if its position is compared to the star alpha Librae (Zubenelgenubi).

On the evening of June 3, Jupiter lies less than one degree to the north of the star. Binoculars will show that the star is a double, and that Jupiter is accompanied by its four large Galilean moons. A broad gibbous Moon lies 3° to the north of Jupiter on June 23. The next planet along the southern horizon is Saturn. This ringed planet comes to opposition on June 27. It is near its greatest distance from the Sun, but the biggest disadvantage for U.K. observers is that it is located in the far southern constellations, and therefore never reaches elevations much greater than 12° above the horizon in Scotland. The long path that its light has to undertake through the atmosphere means that it appears to wobble and undulate unacceptably. It is much better seen from equatorial and southern latitudes. Over the next 15 years it steadily improves its elevation at each successive opposition. Mars is in a somewhat similar situation, as it gradually slows its eastward motion in Capricornus. It reaches a stationary point at the end of June, turning retrograde, but even further to the south. Its elevation only just reaches double figures (degrees) and its only redeeming feature is that it brightness will rapidly increase as it approaches Earth. By the end of June, its magnitude achieves a value of -2.1. The Moon can be seen above Saturn on June 28 and above Mars after midnight on June 30. The low elevation of the planets from our northern climes, along with the persistence of twilight throughout the night means that many amateur astronomers will decide to forego observing in June. Others may like to spend time spotting the many artificial satellites that cross the skies, being still illuminated by the Sun even near local midnight. The burgeoning amount of hardware in orbit means that it is very easy to follow our missions into space.

Moon phases:

  • Last Quarter June 6
  • New Moon: June 13
  • First Quarter: June 20
  • Full Moon: 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. An arrow depicts the motion of Mars