SkyEye

The Calendar

The famous Perseid meteor shower is not unduly bothered by moonlight this year. Jupiter narrowly misses the sixth-magnitude star σ Arietis. In occultation news, the Moon begins a series of obscurations of the first-magnitude star Antares. The ringed planet Saturn arrives at opposition.

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 Leo

Mercury attains a greatest elongation east of 27.4° on 10 August and soon begins its descent back toward the western horizon. The tiny planet is dimming throughout the month, beginning at magnitude +0.1 and ending at third magnitude. With inferior conjunction awaiting early next month, Mercury goes into retrograde on 23 August. Early risers in northern temperate latitudes lose sight of Mercury before the end of the month but the nearest planet to the Sun remains above the horizon until next month for everyone farther south.

Venus Leo → Cancer

The evening star finally vanishes for everyone this month, with inferior conjunction taking place on 13 August. Observers in equatorial and southern regions may still glimpse the bright planet during the first week or so but Venus disappeared from northern temperate skies late last month. It quickly reappears at dawn to begin another apparition as the morning star, a title it will retain for the rest of the year.

Earth and Moon

The Moon is full twice this month, on the first and last days of August. The second Full Moon in a calendar month is popularly called a 'blue moon'. This means that the Moon will be near its new phase when the Perseid meteor shower peaks around mid-month, leaving dark skies for this annual spectacle. In fact, the most distant apogee of the year coincides with New Moon on 16 August. Several first-magnitude stars and one open cluster are approached by the Moon this month. On 9 August, the Pleiades are only 1.5° north of the waning crescent Moon. Four days later, an even slimmer waning crescent Moon passes 1.7° south of the star Pollux. The waxing crescent Moon is found 2.6° north of Spica on 21 August but the main event occurs four days later when the waxing gibbous Moon occults Antares. This series of monthly lunar occultations of the brightest star in the constellation of Scorpius will continue for five years!

Mars Leo → Virgo

An second-magnitude denizen of the evening sky, Mars may be lost to view for observers northern temperate latitudes, low in still-bright twilight skies. Fans of the red planet have a much better chance of spotting Mars in the still-dark winter skies of the southern hemisphere. On the tenth, Mars is less than a degree south of the fourth-magnitude B-type star σ Leonis. The waxing crescent Moon passes 2.2° north of the planet on 19 August. Mars and fourth-magnitude F-type main sequence star Zavijava (β Virginis) are just over 1′ apart four days later on 21 August

Jupiter Aries

The ever-brightening Jupiter reaches west quadrature on 7 July and rises in late evening for all observers. The following day, the Last Quarter Moon passes 2.9° north of the gas giant. Jupiter only just misses occulting the sixth-magnitude star σ Arietis on 21 August; observations of the 1952 occultation of this star by this planet helped astronomers learn more about the composition of Jupiter's atmosphere.

Saturn Aquarius

Saturn arrives at opposition on 27 August. Shining at magnitude +0.5, the rings are open to 9° when viewed through a telescope. Saturn rises as the Sun and is visible all night. The Moon moves 2.5° south of the planet twice this month, on 3 August and again on 30 August.

Uranus Aries

Uranus rises in the late evening hours and may be easiest to spot from northern latitudes. The waning crescent Moon is 2.6° north of the planet on 9 August but later in the month provides better observing opportunities. Uranus is at west quadrature on on 16 August, exactly 90° away from the Sun. The sixth-magnitude planet reaches maximum declination north for the year on 28 August. The following day, Uranus goes into retrograde.

Neptune Pisces

A small telescope is necessary to view the most distant planet in the solar system as it rises mid-evening. Neptune is only 1.5° north of the waning gibbous Moon on 4 August but the blue ice giant is best observed later in the month when the sky is not lit with moonlight.