SkyEye

The Calendar

Summer returns to the northern hemisphere (and winter to the south) when Earth reaches solstice this month. Saturn's rings close to their minimum aspect for the year and observers in southern latitudes are in the middle of an excellent morning apparition of Mercury.

The Solar System

The word planet is derived from the Greek word for 'wanderer'. Unlike the background stars, planets seem to move around the sky, keeping mostly to a narrow track called the ecliptic, the path of the Sun across the stars. Dwarf planets and small solar-system bodies, including comets, are not so constrained, often moving far above or below the ecliptic.

Sun Taurus → Gemini

Mercury Aries → Taurus → Gemini

Best viewed from the southern hemisphere and equatorial regions, Mercury is visible in the east at dawn. A telescope will be necessary to see nearby Neptune on 4 June; the two planets are 2.7° apart in the sky but the sky may be too light to discern the distant ice giant. Mercury continues to brighten this month but it soon heads back toward the horizon so look for it early in the month.

Venus Gemini → Cancer → Leo

Venus reaches theoretical dichotomy and greatest elongation east (45.5°) on the fourth day of the month. Southern hemisphere observers continue see the planet appear a little higher above the western horizon every night although the evening star is in decline for most other latitudes. The magnitude −4.4 planet is just a half of a degree away from the open cluster M44, the Beehive Cluster, on 13 June.

Earth and Moon

Earth reaches solstice on 21 June. The word solstice means 'sun stands still' so that on this day, the solar declination reaches an extreme. In this case, the Sun appears directly over the Tropic of Cancer in the northern hemisphere.

There are no lunar occultations of planets taking place this month but the Moon may be found 1.6° north of Antares on 3 June, almost the same distance south of the open star cluster known as the Pleiades on 16 June, and 1.7° south of Pollux, the brightest star in Gemini, four days later. Moonlight should not unduly inconvenience observations of the June Boötid meteor shower near the end of the month.

Mars Cancer → Leo

Mars continues to favour observers in northern temperate latitudes, not setting until late evening. Planet watchers in the southern hemisphere lose the red planet much earlier. Mars is getting ever farther from Earth but only drops a tenth of a magnitude this month, ending June at +1.7. On the second day of June, Mars is only 0.1° north of M44, an open cluster known Praesepe (Latin for 'manger'). Three days later, Mars is found 1.3° north of the fourth-magnitude δ Cancri, a K-type giant star whose official name, Asellus Australis, means 'southern donkey', one of a pair of donkey feeding from the manger. The waxing crescent Moon glides 3.8° south of the second-magnitude planet on 22 June.

Jupiter Aries

Jupiter is now rising an hour or two after midnight for all latitudes but is best seen in the long dark winter skies of the southern hemisphere. The waning crescent Moon passes 1.5° north of the magnitude −2.1 planet on 14 June.

Saturn Aquarius

The southern hemisphere still has the best views of Saturn, with the bright planet rising in mid-evening. However, by the end of the month, observers further north may see Saturn rise in the east before midnight. The waning gibbous Moon glides 3.0° south of Saturn on 9 June. Four days later, the ringed planet reaches its maximum declination north for the year. The day after that, on 13 June, the rings close to their minimum angle for the year (7.30°). The rings will now open slightly for the next few months. Retrograde motion commences later in the month.

Uranus Aries

Now that it is past conjunction, Uranus is a morning sky object, rising an hour or two ahead of the Sun and best observed from the southern hemisphere. It is found together with Mercury on 4 June but at sixth-magnitude, Uranus will be a challenging object to spot 2.7° south of the brighter inferior planet. The waning crescent Moon passes somewhat closer — 2.0° — on 15 June.

Neptune Pisces

The Moon has been passing ever closer to Neptune each month this year and is found only 2.0° south of the planet on 11 June. West quadrature occurs on 19 June, with Neptune now rising before midnight for all observers. The faint planet reaches its maximum northerly declination for the year on 27 June and begins retrograde motion (in relation to ecliptic longitude) three days later.