The night sky in July 2017

posted 29 Jun 2017, 12:00 by Pete Collins   [ updated 17 Jul 2017, 13:55 ]
by Anne Holt

Sunrise:   1st   04.44        31st    05.23
Sunset     1st   21.48        31st    21.06

Astronomical darkness:   1st    none    31st    00.47 to 01.44

Full Moon   9th       New Moon   23rd

Earth is at aphelion  (the furthest point in its orbit from the sun) on 3rd at 21.11, when it will be at a distance of approx 94.5 million miles  (152 million Km)

Highlights

Yet again there is nothing spectacular to report, we do have some astronomical darkness to look forward to at the end of July - 16  minutes on 30th and almost an hour on 31st.

Pluto reaches opposition on 10th, 4 days before the second anniversary of New Horizons' closest approach.   We now know a lot more about the tiny distant world, which has surprised everyone.

Venus is still shining brightly in the morning sky, but Jupiter is now only prominent in the early part of the night.

We could still see some Noctilucent Clouds after sunset and before sunrise - see previous months' notes for more details.

There are some bright ISS passes from mid month, around 2am or 3am at first, then some before midnight during the last week of the month.

There are still a few faint fuzzies around, especially at the start of the month, and we have a planet occulted by the moon - in daylight.

Constellations

The Summer Triangle (made up of Vega in 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 Gemini, mag -1.1. An evening object, low on the Western horizon after sunset.  At the start of July it sets around 22.30, 50 minutes after the sun.  On 5th it moves into Cancer and into Leo on 17th.  It reaches greatest eastern elongation on 20th. On 25th it is 6 degrees west of the 7% lit waxing moon, close to Regulus in Leo.  The Moon does actually occult the planet earlier that day - too early, as it is in daylight.  By month end it sets at 21.40 and will have faded to mag 0.5.

Venus
:  in Taurus, mag -4.1. Still a very bright morning object, rising at 02.26 on 1st.   When seen through binoculars or a telescope its phase increases during the month, 63% lit on 1st, 74% on 31st. However its apparent size is decreasing as it moves away from us.  On 5th it passes close to the Pleiades star cluster and on 14th is near Aldebaran, the eye of the bull.  On 20th and 21st it is quite close to the waning crescent moon.  On 30th and 31st it spends some time in the non zodiac constellation, Orion.

Mars
:  in Gemini, moving into Cancer on 18th.  Sets too soon after the Sun to be visible in July.

Jupiter
:  in Virgo, mag -2.1. Sets soon after 1am on 1st, on this day the 58% lit moon passes 7 degrees west of the planet.  On 28th they are even closer, separated  by just 2 degrees, low in the south west.   By month end it will have faded slightly to mag -1.9 and set soon after 23.00.

Saturn
:  in Ophiuchus, mag 0.1. Sets just before 4am on 1st, when it culminates around midnight,  On 7th the 95% lit Moon passes 5 degrees to the north.  The rings are still wide open but Saturn remains very low in the sky - as it will for the next few years.  It takes 29 years to make one orbit of the sun, so remains in each zodiac constellation for over 2 years, and won't move north of the celestial equator until at least 2025. ( Can't give an exact date as the tables I use only go up to Dec 2023, when it will be in Aquarius)  At month end it will set at 01.50.

Uranus,  in Pisces, mag 5.9. On 1st it rises at 01.14 and at 23.13 by month end.  Best seen towards the end of July when it reaches an altitude of 25 degrees while the sky is still dark.  Should be visible in binoculars but a telescope is needed to show the small blue/green disc.  On the morning of 15th the 3rd quarter Moon passes 5 degrees south of the planet.

Neptune:  in Aquarius, mag 7.9. Rises a few minutes after midnight on 1st and at 22.06 on 31st.  During the month it brightens very slightly to mag 7.8.  On 31st it culminates at 03.34,  nearly 3 hours before sunrise - though not in the small period of astronomical darkness.   

Dwarf planet Pluto reaches  opposition on 10th, when it culminates at 01.13,  a little SE of the teaspoon asterism in Sagittarius.   At mag 14.8 it is probably too faint to be seen directly in even the best amateur scopes but might be a good photographic target.  Why not try to emulate Clyde Tombaugh and take a couple of pics a few days apart.  Even without the aid of his blink comparator, it should be possible to see what has moved    For its exact position see https://theskylive.com/pluto-info

Meteors

No major showers in July; we have a couple of minor ones towards the end of the month but they have low radiants and are better seen from further south.

Delta Aquarids:  Active July 2th to August 23rd, peak 30th.   ZHR  given as up to 25 but likely to be much lower from our northern latitude.  These are faint, medium paced meteors not usually leaving trails.  Parent comet not known for sure, could possibly be 96P/Macholz

Alpha Capricornids:  Active July 13 to August 15th, ZHR 5.  This shower doesn't have a defined peak but is probably best seen 30th/31st July.  These are slow moving, bright meteors leaving long trails. There could also be some fireballs.  This shower is caused by the Earth passing through debris left by comet 169P/CAT.

The radiants of both these showers are near the ecliptic, opposite the Sun, so it can be difficult to distinguish them from meteors from the antihelion source, which is active in late July.   However, these tend to be rather faster moving than meteors from either of the showers.

The Perseids are active from 11th July, so a few may be seen in the second half of the month, and sporadic activity - meteors not belonging to any particular shower - is usually quite good in July.

Comets

The three faint comets which have been visible in our skies for the last few months are now getting very low, faint and difficult to spot.

71P/Clark: mag 11.2, moving southwards through Scorpio.  At the beinning of July it is above the horizon from around 21.00 to 1am but only reaches an elevation of about 2 degrees.  By month end it is only visible from the southern hemisphere.

V2/Johnson:  mag 8.5.  Starts the month a little east of Spica, then moves southwards.  From mid July is only visible from further south.

4P/Tuttle-Giacobini-Kresak:  mag 7.5.   Yet another now best seen from further south.   Starts the month in Serpens, moving into Scutum on 2nd.

However, we do have one comet whose position is slightly better.  C2015/ER61 PANSTARRS is moving through Aries and into Taurus. Its predicted mag is around 9, but it has shown signs of becomng brighter.  In early July it rises around 1am and by 23.30 at month end, when it will be heading towards the Pleiades.

As always, more info and position details can be found on:
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