SkyEye

The Calendar

Bright Venus pays a visit to the Pleiades open star cluster and a 'Super Moon' lights up Earth. Dark skies make for favourable observing conditions for the meteor showers occurring in the latter part of the 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 Pisces → Aries

Mercury Aquarius → Pisces → Cetus → Pisces → Aries

The nearest planet to the Sun is 1.3° south of the farthest planet from the Sun on the fourth day of the month. Zero-magnitude Mercury will be visible to the naked eye but a telescope will be necessary to spot Neptune in the brightening skies ahead of sunrise. Southern hemisphere observers will have the best chance of catching this unusual meeting during this month's excellent morning apparition. Mercury gets brighter throughout the month, ending at magnitude −1.7 but also quickly loses altitude above the eastern horizon as it heads to superior conjunction in May.

Venus Taurus

The evening star is still best viewed from northern latitudes but it is getting a little lower in the sky after sunset with every passing day. On the third day of the month, Venus passes just 0.3° south of the Pleiades open star cluster. When viewed through a telescope, Venus appears as a crescent, growing slimmer (from 47% illuminated down to 25%) but also increasing in apparent diameter (from 26 arc seconds up to 39) as the planet gets closer to Earth. The planet reaches a magnitude of −4.5 by the end of April.

Earth and Moon

The closest perigee of the year is followed one day later by a Full Moon, resulting in a Super Moon on 8 April. Two meteor showers occur around the time of New Moon on 23 April. Both the Lyrids and the π Puppids benefit from moonless skies. On the last day of April, the First Quarter Moon glides 1.6° north of Praesepe, an open star cluster.

Mars Capricornus

Mars reaches an equinox on 8 April. Spring begins in the southern hemisphere of the red planet and autumn takes hold in the north. Eight days later, the waning crescent Moon moves past Mars at a distance of 2.0°. The red planet rises before midnight for planet watchers in the southern hemisphere but the ecliptic through Capricornus is low to the horizon from northern vantage points and Mars never gets very high in the sky before dawn.

Jupiter Sagittarius

Jupiter continues to brighten as it heads toward opposition in July, beginning the month at magnitude −2.1 and ending at −2.3. The Last Quarter Moon is 2.0° south of the planet on 14 April and the following day, Jupiter reaches west quadrature. The largest planet in the solar system is most easily observed from the southern hemisphere, where it rises before midnight and is high in the sky during the early morning hours.

Saturn Capricornus

Because the two planets are in the same part of the sky, Jupiter and Saturn mimic each other's behaviour. The Last Quarter Moon visits the ringed planet the day after it passes Jupiter. Similarly, Saturn attains west quadrature on 21 April which is six days after Jupiter reaches the same configuration. The distance from Earth to Saturn closes to less than 10 au this month and the gas giant begins to brighten slightly, from magnitude +0.7 to +0.6. Look for Saturn in the morning sky, preferably from the southern hemisphere where it reaches a useful observing altitude before dawn.

Uranus Aries

Uranus is at conjunction this month and is lost in the glare of the Sun.

Neptune Aquarius

Neptune is found in the company of bright Mercury on 4 April when the two planets are 1.3° apart in the morning sky. However, a small telescope is necessary to view the most distant planet in the solar system.