SkyEye

The Calendar

The Perseid meteor shower occurs in dark skies, with the crescent Moon setting before midnight. Both Jupiter and Saturn reach opposition this month.

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 Cancer → Leo

Mercury Cancer → Leo → Virgo

Mercury undergoes superior conjunction on the first day of the month and passes into the morning sky in what becomes the best dawn apparition of the year for southern hemisphere observers. Unfortunately for astronomers in more northerly latitudes, Mercury remains close to the horizon throughout its morning appearance. The smallest planet in the solar system passes 0.1° south of Mars on 19 August with Mercury the brighter object. As is always the case with morning apparitions, Mercury begins very bright and gradually dims to around sixth-magnitude at inferior conjunction but the planet remains at negative magnitudes all this month.

Venus Leo → Virgo

This evening apparition of Venus continues to improve for planet watchers in southern latitudes as the evening star climbs ever higher above the western horizon. When observed through a telescope, Venus appears as a waning gibbous globe, the illuminated portion decreasing from 82% to 73% over the course of the month. At the same time, its apparent diameter is increasing slightly and the planet is beginning to brighten.

Earth and Moon

The annual renewal of the Perseid meteor shower is blessed with dark skies, with the waxing crescent Moon setting early. The Full Moon on 22 August is the third of four Full Moons in the current astronomical season, making it a Blue Moon in the traditional sense. The nearest apogee of the year occurs on the penultimate day of the month.

Mars Leo

Mars and Mercury enjoy a particularly close encounter on 19 August when Mars is just 0.1° north of the tiny inferior planet. The red planet reaches a solstice just six days later when the Martian northern hemisphere enjoys summer and the Martian southern hemisphere is gripped by winter. Mars shines at magnitude +1.8 this month and is getting harder to spot low in the west during evening twilight.

Jupiter Aquarius → Capricornus

The largest of the planets is visible all night this month, rising as the sun sets and vanishing at sunrise. This is because it arrives at opposition on 19 August. During this time it shines at a brilliant magnitude −2.9 and a telescope reveals a disk 49.1 arc-seconds wide. The best views of Jupiter are obtained from the southern hemisphere where the ecliptic is high overhead.

Saturn Aquarius

Saturn is at opposition on the second day of the month. It rises at sunset and is visible all night. Planet watchers in southern latitudes have the best views, with the planet rising high in the sky. Saturn shines at magnitude +0.2 this month with the disk of the planet measuring 18.6 arc-seconds in diameter and the rings 42.3 arc-seconds.

Uranus Aries

The Moon glides past Uranus twice this month, on the first day of August and again on 28 August. The sixth-magnitude planet reaches west quadrature on the seventh and is now rising in the evening hours. Uranus reaches its maximum northerly declination for the year on 19 August and enters into retrograde motion the following day. It will remain in retrograde for the rest of the year.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system. Neptune is rising as the sky gets truly dark and is brightening imperceptively as it approaches opposition next month.