Our celestial neighbourhood in July
PICK OF THE MONTH
Mars
Best time to see: 31 July, 03:30 UT
Altitude: 37˚
Location: Aries
Direction: East-southeast
Features: Phase, surface markings, atmospheric phenomena, polar caps
Recommended equipment: 75mm, or larger
We’re less than six months away from the next opposition of Mars on 8 December 2022, and it’s around this time that the planet starts to improve noticeably week on week. On 1 July, Mars shines at mag. +0.5 and presents a 7 arcsecond disc when viewed through a telescope’s eyepiece.
At this time, instruments 200mm or larger will start to reveal surface features, present as dark markings on the planet’s globe. In addition, the southern polar cap should be visible as a bright ‘spot’ on the southern edge of the planet. Mars will appear 85%-lit on 1 July, the planet’s southern pole tilted towards Earth by 20˚.
By the end of the month, the Red Planet will have brightened slightly to mag. +0.2 and will be presenting an 8 arcsecond disc. The planet’s phase will be 84%-lit on 31 July, the southern pole’s tilt angle having reduced so that it’s inclined to Earth by 14˚. This will move the southern pole a bit further away. At this time, increased warming in the planet’s southern hemisphere will have had an effect on the pole, its appearance naturally reducing.
On 31 July, Mars is located in the constellation of Aries, the Ram, and able to at tain a peak altitude around 21˚ under dark-sky conditions as seen from the UK’s centre. Although low, this is a good time to try and get acquainted with the planet. With increasing dark-sky altitude and a growing apparent size, getting used to the view during July will put you in an excellent place to experience the view of Mars as it approaches opposition in early December. A 35%-lit waning crescent Moon sits 4.5˚ to the east of Mars on the 22nd. On 31 July, Mars will lie 1.8˚ from mag. +5.8 Uranus.
Mercury
Best time to see: 1 July, 30 minutes before sunrise
Altitude: 4˚ (very low)
Location: Taurus
Direction: Northeast
Mercury is a morning planet at the start of July, brightening as it creeps towards the Sun. On 1 July it shines at mag. –0.7 and rises 70 minutes before sunrise. By the 7th, Mercury brightens to mag. –1.22, but rises only 55 minutes before the Sun. The last date of visibility is probably 12 July, when mag. –1.7 Mercury rises above the northeast horizon, 30 minutes before sunrise.
Superior conjunction is on 16 July, after which it emerges into the evening sky but is poorly placed. On 25 July, mag. –1.0 Mercury sets just 35 minutes after the Sun.
Venus
Best time to see: 31 July, 03:45 UT
Altitude: 9˚ (low)
Location: Gemini
Direction: East-northeast
Venus is in the morning sky, shining at mag. –3.8. On 1 July it rises 110 minutes before the Sun, increasing to 120 minutes by July’s end. Telescopically, Venus appears as a gibbous disc, 90%-lit, 10 arcseconds across. A waning crescent Moon is nearby on the mornings of the 26th and 27th.
Jupiter
Best time to see: 31 July, 03:30 UT
Altitude: 38˚
Location: Cetus
Direction: South
Jupiter is a morning planet, but over past weeks its position has been poor, only appearing at low altitude before sunrise. Now we’re past the June solstice, the UK’s night is lengthening and Jupiter is improving. Jupiter is located in the northwest corner of Cetus, the Whale. Shining at mag. –2.4, it is visited by a 65%-lit waxing gibbous Moon on the morning of 19 July, which sits 3˚ south of the planet at 02:00 BST (01:00 UT).
Saturn
Best time to see: 31 July, 01:20 UT
Altitude: 22˚
Location: Capricornus
Direction: South
Things begin to improve for Saturn this month, as we’re past the June solstice. As it approaches opposition on 14 August, Saturn is able to reach its highest position in the sky, due south, in relative darkness from mid-month onwards. A 91%-lit waning gibbous Moon sits below Saturn on the morning of 16 July, the pair rising together around 23:20 BST (22:20 UT) on 15 July.
Uranus
Best time to see: 31 July, 01:30 UT
Altitude: 21˚
Location: Aries
Direction: East
A morning planet, improving in position towards July’s end.
Neptune
Best time to see: 31 July, 01:30 UT
Altitude: 29˚
Location: Pisces
Direction: Southeast
Neptune is poorly located in the morning sky at July’s start, a situation which improves rapidly as the nights lengthen. By July’s end, Neptune reaches an altitude of nearly 30˚ under dark skies. Neptune is in Pisces, but this doesn’t last for long as it slips back into Aquarius in mid-August.
The planets in July
The phase and relative sizes of the planets this month. Each planet is shown with south at the top, to show its orientation through a telescope
Jupiter’s Moons: July
Using a small scope you can spot Jupiter’s biggest moons. Their positions change dramatically over the month, as shown on the diagram. The line by each date represents 01:00 BST (00:00 UT.)
