July 2021

Welcome to SkyEye, your guide to this month's celestial events.

The Calendar

Venus has a busy month, passing close by Praesepe, Mars and Regulus in the space of three weeks. Earth reaches aphelion on 5 July and at the end of the month, the Southern δ Aquariid meteor shower is lost to moonlight.

The phases of the Moon in July 2021

Date Body Event
1 Moon last quarter
3 Venus 0.1° north of the open star cluster M44 (known as Praesepe or the Beehive Cluster)
4 Moon, Uranus 1.9° apart
Mercury greatest elongation west: 21.6°
5 Moon apogee
Earth aphelion
6 Moon ascending node
10 Moon new
13 Mars aphelion
Venus, Mars conjunction: 0.5° apart
17 Moon first quarter
134340 Pluto opposition
19 Mercury ascending node
20 Moon descending node
21 Moon perigee
Venus 1.0° north of Regulus
24 Mercury perihelion
Moon full
29 Mars 0.6° north of Regulus
30 Earth Southern δ Aquariid meteor shower
31 Moon last quarter

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.

The position of the Sun and planets at mid-month

Sun GeminiCancer

Mercury TaurusOrionGeminiCancer

Mercury is visible in eastern skies before dawn. It reaches its greatest elongation west of the Sun (21.6°) on the fourth day of the month. At this point it begins to descend back toward the horizon as seen from the southern hemisphere but observers in northern temperate latitudes will see the bright planet continue to gain altitude for a few more days before it heads downward. Beginning July at a brightness of +1.0, it brightens over two magnitudes during the month. Another perihelion (the third this year) occurs on 24 July. Look for Mercury early in July before it gets too low to the horizon.

Venus CancerLeo

On the third day of the month, southern hemisphere observers will have the best opportunity to see Venus come within 0.1° of the open star cluster Praesepe or M44. The evening star is half a degree north of Mars just ten days later but Venus is five magnitudes brighter than the red planet. Venus also outshines Regulus when the two come close together on 21 July. Venus remains close to the western horizon for astronomers in northern temperate latitudes and the long twilight of summer may make observing the evening star problematical.

Earth and Moon

Earth reaches aphelion, the point in its orbit when it's farthest from the Sun, on 5 July. The major meteor shower of the month, the Southern δ Aquariids, is obliterated by the light of the waxing gibbous Moon near the end of July.

Mars CancerLeo

Like Earth, Mars reaches aphelion this month with the red planet farthest from the Sun on 13 July. Coincidentally, it is only half a degree from Venus on the same day. Mars passes first-magnitude star Regulus on 29 July. The second-magnitude planet is visible in the west after sunset but is getting increasingly difficult to see from northern latitudes. Southern hemisphere observers may have a slightly easier time spotting the planet.

Jupiter Aquarius

Jupiter reaches opposition next month so its rising time is getting ever closer to sunset. The gas giant appears in the east in the early evening hours and is best viewed from the southern hemisphere where winter skies darken early.

Saturn Capricornus

Saturn is rising ever earlier in the evening ahead of next month's opposition. Although best observed from southern latitudes, northern planet watchers are finally getting a look at the ringed planet as it rises during the evening twilight. Saturn's magnitude increases from +0.4 to +0.2 at the end of the month.

Uranus Aries

Best viewed from the southern hemisphere where sunrise comes late, Uranus is a morning sky object, rising around midnight. The waning crescent Moon passes 1.9° south of the faint planet on 4 July.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system. Northern hemisphere observers are finally seeing Neptune rise before midnight but the best views of this elusive object are from southern latitudes on those nights when the Moon is absent from the sky.

The Celestial Sphere

Constellations are patterns of stars in the sky. The International Astronomical Union recognises 88 different constellations. The brightest stars as seen from the Earth are easy to spot but do you know their proper names? With a set of binoculars you can look for fainter objects such as nebulae and galaxies and star clusters or some of the closest stars to the Sun.

Descriptions of the sky for observers in both the northern and southern hemispheres are available for the following times this month. Subtract one hour from your local time if summer (daylight savings) time is in effect.

Local Time Mid-month Northern Hemisphere Equator Southern Hemisphere
1730 hours (1830 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
1930 hours (2030 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
2130 hours (2230 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
2330 hours (0030 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
0130 hours (0230 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
0330 hours (0430 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S
0530 hours (0630 hours summer time) 60° N 50° N 40° N 30° N 20° N 10° N 10° S 20° S 30° S 40° S