SkyEye

The Calendar

A deep penumbral lunar eclipse takes place early in May and a very old crescent Moon occults Jupiter in dawn skies mid-month. Venus continues to reign supreme for northern hemisphere observers as the evening star.

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 Aries → Taurus

Mercury Aries

Mercury goes from one extreme to another this month, beginning the month at inferior conjunction, after which it soars in the morning sky for observers in the southern hemisphere (the best morning apparition of the year for these latitudes), and finally arriving at greatest elongation west (24.9°) on 29 May. However, this is a poor dawn apparition for those seeking this elusive planet from northern temperate regions. Mercury returns to direct motion mid-month. Brightening steadily, it is best viewed toward the end of May.

Venus Taurus → Gemini

For observers in northern temperate latitudes, Venus's climb above the western horizon comes to an abrupt halt; the evening star will be in decline for the remainder of this apparition. However, the views just get better for those south of the equator. Venus continues to slowly brighten, from magnitude −4.1 to −4.2 this month, and the waxing crescent Moon is 2.2° north of the planet on 23 May.

Earth and Moon

The η Aquariid meteor shower is washed out by the Full Moon on 5 May. The faint penumbral lunar eclipse will not darken the light of the Moon appreciably. One planet is occulted by the Moon this month, with Jupiter falling victim on 17 May. The waning gibbous Moon passes 1.5° north of first-magnitude Antares on 7 May. The Moon is too close to the Sun to observe its passage by the Pleiades this month but the waxing crescent Moon is easy to spot on 24 May when it is 1.6° south of Pollux, the brightest star in Gemini.

Mars Gemini → Cancer

Observers in the southern hemisphere should look for the red planet early in the evening as it sets around four hours after sunset. Northern astronomers hold on to Mars until around midnight. The planet continues to dim, from magnitude +1.3 to +1.6 this month, as it moves across Gemini and Cancer. However, it still outshines the fourth-magnitude κ Geminorum as the planet passes 1.4° south of the binary star on 10 May. The waxing crescent Moon gives Mars a wide berth this month, coming no closer than 3.8° on 24 May. Mars reaches aphelion on the penultimate day of May.

Jupiter Pisces → Aries

Southern hemisphere observers have much the best views of this morning sky object, with Jupiter only just clearing the horizon before sunrise for astronomers in northern temperate latitudes. Jupiter is brightening now that it is past conjunction and is a brilliant magnitude −2.0 this month. It passes 0.6° north of the fourth-magnitude G-type giant star Torcular or ο Piscium on 8 May. The waning crescent Moon occults Jupiter on 17 May beginning around 11:00 UT.

Saturn Aquarius

Saturn is found 3.3° north of the Moon on 13 May. Reaching west quadrature on 28 May, the first-magnitude planet rises before midnight for observers in the southern hemisphere. However, it remains strictly a morning sky object from northern temperate latitudes.

Uranus Aries

Uranus is at conjunction this month and not visible in the night sky. Observers in the southern hemisphere may spot the sixth-magnitude planet as it passes 0.6° south of the sixth-magnitude star 53 Arietis. 53 Arietis is a variable blue, B-type main sequence star. Can you see any colour difference between the planetary and stellar objects?

Neptune Pisces

A small telescope is necessary to view the most distant planet in the solar system. Neptune rises ahead of the Sun but is most easily observed during the early morning hours from the southern hemisphere where the ecliptic rises high overhead. The waning crescent Moon is only 2.2° south of the eighth-magnitude object on 15 May.