SkyEye

The Calendar

The Moon occults bright red Mars this month and Venus reaches greatest elongation west in the morning skies. The famous Perseid meteor shower is somewhat obscured by the light of the last quarter Moon.

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 Gem → Cancer → Leo

Mercury is a morning sky object, best viewed from northern latitudes. However, it is already heading back toward the horizon, vanishing in the east before superior conjunction on 17 August. (A close encounter with the Moon two days after conjunction is unobservable.) It rapidly reappears in the west after sunset in what will be the best evening apparition of the year for observers in the southern hemisphere. Mercury is quite bright in August, ending the month at magnitude −0.6. The closest planet to the Sun reaches perihelion for the third time this year on 6 August.

Venus Taurus → Orion → Gemini

The morning star reaches a greatest elongation west of 45.8° on 13 August. Early in the month the bright planet appears as a waxing crescent in a telescope but it evolves into a waxing gibbous figure by the end. The magnitude of Venus stays fairly steady at −4.2. This evening apparition favours observers in the northern hemisphere, with those in temperate latitudes watching Venus continuing to gain altitude above the eastern horizon into next month.

Earth and Moon

The waning gibbous Moon occults Mars on 9 August and the waning crescent Moon slightly interferes with the famous Perseid meteor shower three days later.

Mars Pisces

Mars reaches perihelion, the point in its orbit where it's nearest to the Sun, on 3 August. Six days later, the waning gibbous Moon occults the red planet. This event is visible from southern South America and parts of Antarctica, and begins around 06:45 UT. Mars rises mid-evening, brightening from magnitude −1.1 to −1.8 over the course of the month, and is most easily observed from the southern hemisphere where it is found high in the night sky.

Jupiter Sagittarius

Now past opposition, Jupiter is already up by the time the sky darkens. It is a brilliant magnitude −2.7 and still looms large in even modest telescopes. Its position in the constellation of Sagittarius means it is easier to observe from southern latitudes where the ecliptic is higher in the sky. The waxing gibbous Moon passes within 1.5° of the planet twice, on the first day of the month and again on 29 August.

Saturn Sagittarius

The ringed planet is also past opposition and visible in the evening sky. It shines at magnitude +0.1 for most of the month and is best seen from the southern hemisphere where it rises high in the sky. The waxing gibbous Moon is found just over 2° away from Saturn on both 2 August and 29 August.

Uranus Aries

The green ice giant attains west quadrature on 2 August. It reaches its most northerly declination of the year (+14.5°) on 14 August and enters into retrograde motion the following day. (Uranus will remain in retrograde until next January.) Look for this sixth-magnitude object in late evening or after midnight on a dark, moonless night.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system. Neptune is approaching opposition next month and rises earlier every evening. Like its neighbour Uranus, Neptune is best sought on a dark night.