SkyEye

The Calendar

Look for red Mars as it traverses the constellation Taurus, passing two bright open clusters and the first-magnitude star Aldebaran.

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

The southern hemisphere is the place to be in order to observe the dawn appulse of Mercury and Neptune on 2 April. The closest planet to the Sun reaches its second aphelion of the year on 10 April and then attains greatest elongation west the following day. At 27.7°, this is the largest elongation for Mercury in 2019.

Venus Aquarius → Pisces → Cetus → Pisces

Venus has dimmed to a still respectable magnitude −3.9 where it will remain for most of the rest of the year. Its phase is increasing (up to 88% by the end of the month) but it is getting ever more distant from Earth as it heads toward superior conjunction. The morning star is an impressive object when seen from tropical and southern latitudes where it rises more than two hours ahead of the Sun, but it remains fairly low in the east for northern hemisphere early risers. A telescope reveals Venus and Neptune to be only 0.3° apart on 10 April. Eight days later, Venus reaches aphelion.

Earth and Moon

Both the Lyrid and π Puppid meteor showers fall victim to the waning gibbous Moon.

Mars Taurus

Unlike many of the other outer planets, Mars is most favourably situated for northern hemisphere observation this month. It continues it journey past the sights of Taurus — M45 (the Pleiades), C41 (the Hyades), and bright Aldebaran — as it continues to dim (now magnitude +1.6) in the early evening sky.

Jupiter Ophiuchus

Jupiter continues to brighten as it approaches opposition in June and now shines at magnitude −2.3. The largest planet in the solar system remains near the horizon when viewed from northern temperate latitudes but is well aloft as observed from the tropics and the southern hemisphere. Jupiter reaches a stationary point on 10 April and goes into retrograde motion. On 23 April, the waning gibbous Moon passes less than 2° north of the planet.

Saturn Sagittarius

Quadrature is an interesting time to observe Saturn telescopically. The shadows of the planet, its rings and its bright satellites are cast noticeably to one side, leading to an eerie three-dimensional effect. West quadrature occurs on 10 April. Another lunar occultation takes place on 25 April when, beginning around 12:15 UT, the Moon eclipses the ringed planet. Retrograde motion commences on the last day of the month. Saturn is a morning sky object which is easiest to see from equatorial and southern latitudes.

Uranus Aries

Uranus is at conjunction on 23 April and is not visible.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system but special care must be taken this month due to Neptune's proximity to the Sun following last month's conjunction. It is less than half a degree south of Mercury on the second day of the month and has an even closer encounter with bright Venus on 10 April. This blue ice giant now rises ahead of the Sun and is best viewed from southern latitudes.