SkyEye

The Calendar

A possible naked-eye comet reaches perihelion early in the month. The third of four penumbral lunar eclipses takes place on 5 July. Venus takes command of the eastern skies before sunrise and is found in the company of Aldebaran on 11 July. Late in the month, all seven planets are in the sky at once! However, you will need a low horizon and an early start because this event happens before dawn. Mercury, Jupiter and Saturn are all desperately close to the horizon and a small telescope will be necessary to spot Uranus and Neptune in lightening skies.

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 Gemini → Cancer

Mercury Gemini

Mercury is at inferior conjunction on the first day of the month, after which it is a morning sky planet. On 12 July it resumes direct motion and ten days later reaches greatest elongation west (20.1°). This morning apparition is best viewed from equatorial latitudes but it is certainly visible both farther north and south. As with all morning apparitions of Mercury, the tiny planet begins as a faint fifth- or sixth-magnitude object and steadily brightens throughout the month.

Venus Taurus

The morning star, brilliantly illuminated at magnitude −4.5, continues its climb above the eastern horizon at sunrise. This dawn apparition favours the northern hemisphere. Venus reaches aphelion on 10 July. The following day finds the bright planet just 1.0° north of first-magnitude Aldebaran. Venus is distancing itself from Earth, growing smaller in apparent angular diameter and at the same time becoming more fully illuminated (19% at the beginning of the month and 43% at the end).

Earth and Moon

Earth arrives at aphelion on the fourth day of the month and the third of four penumbral lunar eclipses occurs the following day. The Southern δ Aquariid meteor shower at the end of the month is slightly impacted by the light of the waxing gibbous Moon.

Mars Pisces → Cetus → Pisces

The red planet spends the rest of the year in the faint constellation of Pisces (and briefly Cetus). The waning gibbous Moon is just 2.0° south of Mars on 11 July. When viewed through a telescope, Mars still presents a distinctly gibbous appearance, being about 85% illuminated this month. It is approaching Earth and opposition, and grows brighter every night, ending the month at magnitude −1.1.

Jupiter Sagittarius

Jupiter is approximately 2° away from the Full Moon when our satellite is eclipsed on 5 July. The gas giant reaches opposition on 14 July, shining at magnitude −2.8 and measuring 47.6 arc-seconds across. Only Venus near inferior conjunction can appear larger. Jupiter is opposite the Sun in the sky so it rises at sunset and sets at sunrise. It is best viewed from the southern hemisphere where the ecliptic is high overhead.

Saturn Capricornus → Sagittarius

Saturn also has an encounter with the Moon. This occurs on 6 July, the day after the Moon passes by Jupiter. The ringed planet also comes to opposition this month. On 20 July, Saturn is directly opposite to the Sun and reaches a maximum brightness for the year of magnitude +0.2. Like its neighbour Jupiter, Saturn rises as the Sun sets and sets when the Sun comes up.

Uranus Aries

Uranus is best viewed after midnight after it has gained some useful altitude. It closes to within 20 au of Earth by the end of the month but remains a sixth-magnitude object. Choose a moonless night later in the month to go looking for it.

Neptune Aquarius

The farthest planet from the Sun rises before midnight but is best observed in the early morning hours when the Moon is below the horizon. A small telescope is necessary to view the most distant planet in the solar system.