The night sky in July 2021
Post date: Jun 28, 2021 7:42:33 PM
by Anne Holt
Sunrise 1st: 04.44 31st: 05.23
Sunset 1st: 21.40 31st: 21.06
Astronomical darkness. None till 30th: 01.06 to 01.24 31st: 00.46 to 01.44
Astronomical twilight. 1st: 00.04 to 02.21
Day length 1st: 16.55.52 31st: 15.43.07
Earth is at aphelion at 23.27 on 5th, when it will be 1.02 AU from the Sun, which will have an angular diameter of 31’ 27”
New Moon: 10th at 02.16 (passes 3 degrees 10’ north of the Sun)
Full Moon: 24th at 03.36 (angular diameter 32’ 20”)
Lunar apogee: 5th at 14.49 (405341Km, angular diameter 29’ 27”)
Lunar perigee: 21st at 10.31 (364519Km, angular diameter 32’ 45”)
July’s full Moon is most commonly known as the Buck Moon, because this is the time when deer are growing new antlers. Other names given in the Old Farmers Almanac are the Wort Moon, the Salmon Moon and the Thunder Moon.
It was the Colonial American Summer Moon, the Medieval English Mead Moon, the old English/Anglo Saxon Hay Moon and the Celtic Corn Moon or Claiming Moon - tried Googling that one to find out what they were claiming at this time, but all I could find was ‘Who owns the Moon?’ articles, the fact that 20% of Americans still claim that the Moon landings were faked - and a Scottish butcher who was over the Moon when his sausages claimed first prize in a competition.
The Neo Pagan name is the Rose Moon and for the Chinese it’s the Hungry Ghost Moon (not the Hungary Moon, as given in one site). The Inuit called it the Dry Moon - it doesn’t say whether this refers to the weather or their alcohol consumption.
Among the many Indigenous American names are the Cherokee Ripe Corn Moon, the Cree’s Feather Moulting Moon and the Algonquin and Ojibwa‘s Raspberry Moon.
The Dakota name is The Moon when the Chokecherries are ripe. These are a species native to N America, so called because the fruit, though edible, is very sour.
Highlights
We have some astronomical darkness at the end of July - 18 minutes on the night of 30th/31st and nearly an hour on the following night. The days are getting shorter, good news for astronomers as, of course, that means the nights are getting longer. Jupiter and Saturn are reasonably high in the morning sky, Jupiter very bright, Saturn much less so. However, at the end of July Saturn’s rings will appear much brighter as it approaches opposition in early August. Uranus and Neptune start the month very low in the pre dawn sky but both reach around 30 degrees in darkness by month end.
The one reasonably active meteor shower will, unfortunately, be marred by moonlight and the fact that the radiant is very low when seen from the Manchester area. There are some bright late evening passes of the International Space Station from 15th to 25th.
But, if any experienced astrophotographers want to have a go at imaging a comet which was in the news not so long ago, it might be worth trying at the end of July, when 67P/Churyumov-Gerasimenko should be around mag 11 and reaching 30 degrees by dawn.
And 12th is the 60th anniversary of cosmonaut Yuri Gagarin’s day in Manchester - the only place outside London which he visited on his trip to the UK.
Constellations
The Summer Triangle asterism (made up of Vega in the constellation of Lyra, Deneb in Cygnus and Altair in Aquila) is now quite high in the southern half of the sky. Cygnus, with its Northern Cross asterism, and Lyra are particularly prominent.
At the start of the month Pegasus, followed by Andromeda, is rising in the early hours.
As always during the summer months, it isn't the best time to see the zodiac constellations or planets as the ecliptic never gets very high in the sky. However, if you do happen to visit a dark sky site over the next few months you should be rewarded with good views of the Milky Way high overhead running through Cygnus and down to Sagittarius just above the southern horizon.
Planets
Mercury: in Taurus, mag 0.8
Very low in the pre dawn sky, so difficult to spot throughout July. On 1st it is still a couple of degrees below the horizon as the sky begins to brighten, rising almost an hour before the Sun, at 03.56. On 5th it is at greatest western elongation, 21 degrees 35’ from the Sun but, because of the very shallow angle of the ecliptic at this time, still failing to clear the horizon by dawn, and only reaching 10 degrees by sunrise. On 8th the very thin crescent Moon passes 3 degrees 45’ north of the planet at 05.39 but they are only 20 degrees from the Sun, with Mercury 2 degrees above the horizon at dawn. It is briefly in Orion on 11th and 12th, when it is at its highest point in the morning sky - still only getting to 4 degrees in relative darkness. It moves into Gemini on 13th, now at mag -0.5, and is at perihelion, 31AU from the Sun, on 24th brighter at mag -1.4 but down to 3 degrees as the sky brightens. When it moves into Cancer on 28th it appears only 5 degrees from the Sun, down to 2 degrees on 31st. It’s a pity we won’t be able to see it as it will be at its brightest - mag -2.1.
Venus: in Cancer, mag -3.9
Very low in the evening sky but, because of its brightness, should be visible from a site with a clear western horizon. On 1st it is 6 degrees above the horizon as the sky darkens, setting at 23.06. On 12th, now in Leo, the 8% Moon passes 3 degrees 15’ north of the planet at 10.09. At dusk the pair are separated by about 5 degrees. Mars is also close by, just over half a degree from Venus, but hardly visible as it is so much fainter. The 2 planets are a few arcminutes closer on the evening of 13th, with the Moon now further to the east. On 21st Venus passes just over one degree north of Regulus, Alpha Leonis, at 21.30 and on 31st is still only 5 degrees above the horizon at dusk, setting at 22.14.
Mars: in Cancer, mag 1.8
Close to Venus in the first half of the month, 6 degrees separation on 1st but, because it is so much fainter, much more difficult to spot in the still bright sky. By the time it is dark enough Mars has sunk below the horizon. It sets at 23.21 on 1st and on 11th, when it moves into Leo, is 2 degrees below the horizon at dusk. It is closest to Venus, less than half a degree apart, on 13th.
If you do decide to try to find it through binoculars, REMEMBER - make sure that the Sun has completely set before looking in that direction. You don’t want Mars to be the last thing that you ever see.
It is also at aphelion on this day, at a distance of 1.67AU from the Sun. By 31st it is 5 degrees below the horizon as the sky darkens, setting at 21.57.
Jupiter: in Aquarius, mag -2.7
Shining brightly in the morning sky. On 1st it rises at 23.52 and should be high enough to be easily seen by 1am. It reaches 24 degrees in the south as the sky brightens soon after 4am. After the first week in July it culminates in relative darkness, on 9th it reaches 7 degrees in the SE by 00.22 and culminates at 04.15, a few minutes before dawn. On this day the two smaller Galilean moons, Io and Europa, are only 3” apart at 02.43, a little to the west of the planet. On the morning of 26th the 92% Moon passes 4 degrees 10’ to the south at 02.21, slightly closer, 3 degrees 55’, at 04.49 as Jupiter fades from view in the brightening sky. On 31st it culminates at 02.41, slightly lower at 23 degrees, and should be easily visible until dawn breaks at around 5am, now down to 18 degrees in the SW.
Saturn: in Capricorn, mag 0.4
Now around 20 degrees west of Jupiter. On 1st it rises at 23.10 and reaches 10 degrees in the SE by 1am, culminating at 03.31, when it is 18 degrees above the southern horizon, and remaining visible for a short while longer. On 24th the full Moon passes 3 degrees 48’ to the south at 17.38. When Saturn becomes visible around 11pm, the separation is just over 5 degrees, with the Moon to the SE. On 31st, now slightly brighter at mag 0.2, it is 10 degrees in the east at 11pm, culminates at 01.27 and is down to 10 degrees by dawn. By this time Saturn is just a couple of days from opposition so the rings will appear noticeably brighter as the Sun shines directly on to them, reflecting almost all of the light back towards us, also the shadows of the small bodies which compose the rings are directly behind them at this time, rather than to the side, causing a dimming effect. The rings are tilted towards Earth by 18 degrees, making them a beautiful sight in even a fairly small telescope.
Uranus: in Aries, mag 5.8
Not visible until late July. On the morning of 5th the crescent Moon is 5 degrees 30’ to the west at 3am, but the planet will be very low, having risen at 01.27 and reaching only 3 degrees by dawn. On 19th, when it rises at 00.34 and gets to 18 degrees by dawn, mag 11.6 (maybe) comet 4P/Faye is just 1 degree north of the planet in the pre dawn sky. On 31st Uranus rises at 23.48 and becomes visible around 02.20, reaching 30 degrees before becoming lost in the brightening sky at 03.30.
Neptune: in Aquarius, mag 7.9
Another morning object, high enough for observing or imaging from mid month. On 1st it rises at 00.26 but only reaches 11 degrees in darkness. On 13th it rises at 23.38 and should be high enough for a short while just before 02.30, when it reaches 22 degrees in the SE. On 28th the gibbous Moon passes 5 degrees SE of the planet at 1am, both quite low in the sky. On 31st it rises at 22.28 and is high enough for imaging or telescopic observation from 01.15 until dawn, when it will be at 31 degrees in the south.
Dwarf Planets
Ceres: in Aries, mag 9.3
Very low in the morning sky, on 1st it is still 7 degrees below the horizon at dawn and on 7th, when it moves into Taurus, it is 2 degrees below. It gets higher during the month, on 31st it rises at 01.07 but only gets to 19 degrees before the sky brightens.
Pluto: in Sagittarius, mag 14.9
Is at opposition on 18th but is still too low for successful imaging or telescopic observing. It culminates at 01.16 but is only 13 degrees above the southern horizon.
Haumea: in Bootes, mag 17.4
Well placed for imaging for a couple of hours in early July. On 1st it is at 32 degrees in the west as the sky gets dark soon after midnight, sinking to 22 degrees as it begins to brighten again. By 31st it is only well placed for less than an hour from around 11pm, when it is at 28 degrees in the west.
Makemake: in Coma Berenices, Mag 17.2
Slightly lower than Haumea, on 1st it is at 27 degrees in the west as the sky gets dark enough at around 00.35, remaining high for only 30 minutes and setting at 04.04. By 31st this is down to only 15 minutes from 23.00, setting at 02.06.
Eris: in Cetus, mag 18.8
Very faint, but within the reach of the best amateur astrophotographers at the end of July. On 1st it is still 5 degrees below the horizon at dawn, but by 31st it should be high enough for imaging for about 20 minutes after 03.00, when it reaches 24 degrees in the SE.
Asteroids at Opposition
6 Hebe: in Aquila, mag 8.4
At opposition on 19th, when it is 1.27AU from Earth. Visible from 23.43, when it is at 23 degrees in the south, culminating a couple of degrees higher at 01.43 and down to 22 degrees in the SW by dawn.
12 Victoria: In Aquila, mag 8.8
Opposition on 30th at 0.834AU from Earth. It will be visible throughout the hour of darkness. It is at 30 degrees in the SE as the sky darkens soon after 11pm, culminating, 35 degrees in the south, at 01.02, sinking to 25 degrees in the SW by dawn.
Comets
Still nothing spectacular predicted but, at the end of July, good astrophotographers will have their first chance of imaging a comet, well known since it was visited by a spacecraft in 2014.
67P/Churyumov-Gerasimenko: in Cetus, mag 12.2
Predicted to reach mag 8.8 in November, when it will be high in the sky, but is very faint and very low at the moment. On 1st it rises at 01.05 but is only 5 degrees above the horizon by dawn. Towards the end of the month it will be reasonably high in the morning sky for a short time. On 20th, now in Pisces, it rises at 00.05 and is at 22 degrees in the SE for a few minutes from 02.47 until the sky brightens. By 31st, now at mag 11.2, it rises at 23.39 and will be high enough for imaging from 02.15, reaching 31 degrees in the SE by dawn, a little over an hour later.
C/2020 T2 (Palomar): in Bootes, mag 10
Only high enough for imaging during the first few days in July. On 1st it should be observable for a few minutes, soon after 00.30, when it will be at 23 degrees in the west, setting at 03.23. By 7th, when it moves into Virgo, it is only 21 degrees at dusk, setting at 02.50. It is at perihelion, 2.05 AU from the Sun, on 10th but is only 18 degrees at dusk. By 31st, down to mag 10.4, it is 13 degrees in the west as the sky darkens, setting at 00.45.
15P/Finlay: in Aries, mag 8.7
Its position is improving but not enough yet for successful imaging. At the start of July it is still below the horizon at dawn. It goes into Taurus on 10th and is at perihelion on 14th at a distance of 1 AU from the Sun, but still only 7 degrees at dawn. On 31st, now slightly fainter at mag 9, it rises at 00.58 and gets to 18 degrees in reasonable darkness.
4P/Faye: in Aries, mag around 12
Only worth mentioning because it is close to Uranus, about 1 degree to the north, on 19th. However on this night they are both too low for imaging, Faye rises at 00.29 and reaches 19 degrees by dawn. By 31st, when it reaches 22 degrees by 3am, the separation is 8 degrees.
Meteor Showers
Three showers have their peak at the end of July but all have low radiants and are better seen from further south.
Piscis Austrinids
Active July 3rd to August 15th, peak 28/29th, ZHR 5 (from Manchester, maybe 1 - if you’re lucky)
These are fairly slow moving, quite bright, meteors, best chance of seeing one or two is before dawn on 29th.
Alpha Capricornids
Active July 3rd to August 15th, peak 29/30th, ZHR 5 (from Manchester maybe 2)
The radiant is highest at 1am so the shower is best seen before dawn on 30th. They are slow moving meteors, worth looking out for because the shower often includes bright fireballs. Parent comet 169P/NEAT.
Southern Delta Aquarids
Active July 13th to August 12th, peak on the night of 29/30th but often shows good rates for about a week centred on that date, ZHR 25 (from the darker areas of Manchester, around 8). The radiant rises at 22.44 and culminates at 03.00, so this is another shower best seen just before dawn. These are faint, medium paced meteors with no trails. Parent comet P/2008 Y12 (SOHO)
All these showers, especially the faint S Delta Aquarids, will be affected by the gibbous Moon, which rises before midnight on 28th and 29th.
The Antihelion Source (ANT)
Meteors not attributed to any specific shower, having a radiant close to the ecliptic directly opposite the position of the Sun.
It is active in July ZHR 2-3. The radiant is close to that of the Capricornids but the meteors are easily distinguishable as the Capricornids are much slower moving.
Credits
Most of the solar system information given here is from:
More information, exact co-ordinates and finder charts of all solar system objects can be found on this site.
Also quite useful is https://theskylive.com
https://www.imo.net/resources/calendar/
https://www.timeanddate.com
Other information is from various internet sources, including NASA, Britannica, Space Facts, Universe Today and, when all else fails,Wikipedia.