Night Sky Notes – July 2017

Night Sky Notes for July 2017               Geoff Mitchell

The summer solstice (June 21st) has now passed; the Earth reaches Aphelion (furthest point of its orbit around the Sun on July 3rd at a distance of 152 million km (95 million miles) and the evening twilight noticeably fades earlier throughout the month. The July night sky shows the summer constellations prominently in the south east from late evening and the late spring constellations disappear into the western twilight. The bright planet Jupiter is now low in the evening twilight, Jupiter set less than two hours after the Sun by month end. Currently the NASA Juno spacecraft is orbiting Jupiter, the first planet in our Solar system to be formed as the latest data from Juno suggest in new theories about how the early solar system formed.

Saturn is found low in the southern aspect in the constellation of Ophiuchus.  This favours more southern observers as all the planets are low in UK skies. Saturn’s ring system is now wide open, a classic view of this gem of the solar system. Small telescopes will show the rings and the brightest moon Titan. Larger telescopes show up to six or so fainter moons and any white oval features on the planets disk.  On the evening of Saturday July 15th a local public open observing evening is planned as part of the Bradgers Hill s weekend events (refer to the home page for more information) .

The summer night sky contains many fine objects to view for the enthusiast in the late evening hours but also has a few notable events of special interest.  Look to the NW from around 90 minutes to 120 minutes after sunset or similarly to the NE hours before sunrise, when the Sun just below the horizon during the summer months. In the right conditions extremely high clouds at 80 km altitude known as Noctilucent Cloud (NLC) may be seen, NLC’s show a bluish colour and also show filamentary structure.

Our own Milky Way galaxy stretches from the constellation of Auriga [The Charioteer], marked by the bright star Capella and through the constellations of Perseus and Cassiopeia all now positioned low in the north.

In the south east the summer constellation of Cygnus [The Swan] now seen as evening twilight fades. The Milky Way can be seen as a faint band of stars stretching low in the east down through constellations of Aquila [The Eagle], Scutum [The Shield] and towards Sagittarius [The Archer] and Scorpius [The Scorpion] in late evening skies, use binoculars to see the myriad of stars in these rich star clouds, best seen on clear dark moonless evenings from darker locations outside the town.  Sagittarius is best seen in July, the constellation is known for the `Teapot` asterism of stars has rich star fields and some fine star clusters  located above the spout of the Teapot  asterism; however you do need a good southern horizon and finder chart ( see notes ) to spot some of these. Dwarf planet Pluto is located just above `the handle of the teapot asterism`.

Hercules is noted for the Globular cluster M13 containing some 750,000 stars, a nice view in a small telescope The bright star Vega in the constellation of Lyra [The Lyre] is seen low above the north east horizon and Altair in the constellation of Aquila low in the east. Vega, Altair and Deneb, in the constellation of Cygnus form the `Summer Triangle` asterism, a useful sign post for the summer skies.

Look low in the southern aspect late evening to find the distinctive `T` shaped asterism of stars of the `head` of Scorpius . Although rather low as seen from the UK, look below the `T` head of Scorpius to see the `blood red` coloured star Antares.  Antares name means `The rival of Mars`, a red super giant star, with a mass of some 20 solar masses. It has a diameter that, on the scale of our solar system, would be greater than the orbit of Mars. High in the south the bright orange star Arcturus in the constellation of Bootes [The Herdsman] is the brightest star in the northern hemisphere of the sky.

 

 

Planets in July 2017

Mercury is visible low in the evening twilight (after sunset) in mid July, setting an hour after sunset. Greatest elongation occurs in late July.  On the evening of July 25th a thin 7.9% waxing crescent Moon is found just above Mercury (Visible from 21:15 BST) very low in the western aspect.

Venus is positioned low in the east, visible in morning twilight rising some two hours before sunrise.

Mars is now positioned in the daytime skies, with conjunction on July 27th.

Jupiter heads into the evening twilight and is past its best for observation, cloud belt and Galilean moons visible using a small telescope.

Saturn now just past opposition, low in the south in Ophiuchus – a good time to see this ringed `gem`.

Uranus is placed in our– best views in autumn skies.

Neptune is placed in our midnight skies – best views in autumn skies.

Dwarf planet Pluto reaches opposition on July 10th in the Teaspoon asterism in Sagittarius, visible as a faint 14.2m magnitude star.

Moons phases in July 2017

New Moon          July 24th                 Moonless, best time for deep sky observing.

First Quarter     July 1st                  Best days to see shadow details in lunar craters (early evening)

Full Moon           July 9th                    Best days to see bright ray craters like Copernicus / Tycho.

Last Quarter      July 16th                 Moon visible in daytime skies.  Do not look directly at the Sun.

Meteor shower s                             Southern δ Aquarids, maxima around 28th July, favourable ZHR 20 / hour

Capricornids, several maxima in July, bright yellow / blue meteors, low rates.

The Highlights of the Month

Mercury briefly visible (25 minutes after sunset) low in evening twilight skies mid month.

Saturn is low in southern aspect; rings almost wide open at 26° DE [tilt] showing Saturn’s North Pole.

Scutum, Sagittarius and Scorpius are visible low in the south as twilight fades. Good star fields seen on moonless evenings. Also note the deep red colour of star Antares ` the rival of Mars ` in Scorpius and globular cluster M4.

Noctilucent cloud – watch the NW skies from 90 to 120 minutes after sunset to see these electric blue clouds.

More detailed sky notes and LAS Newsletters, Finder charts are available to LAS members via the Members` page on the LAS Website www.lutonastrolink.org.uk  Artificial satellite and International Space Station visible passes and bright Iridium flares – check the  home page for posting s of details of favourable observing times.

Waxing  crescent Moon visibility    . Caution.  Do NOT look at the Sun directly with or without optical aid.

A very thin, 2.9% waxing crescent 1½ day old moon is visible after sunset from around 21.15 to moonset 21.40 BST on July 24th. On the evening of 25th July the thin 7.9% waxing crescent Moon will be more readily seen  with Mercury to the lower right , visible after sunset from around 21:15 until moonset at 22:12 BST.  Note the dimly lit part visible by Earthshine is readily seen with binoculars or small telescope.  Only look for the crescent Moon after the sun has completely set. 

Sky looking south at 11pm British Summer Time (BST), mid July 2017

July - South

In the south the ringed planet Saturn currently is located in Ophiuchus, just east of the `T` shaped asterism of the head of Scorpius. From the UK we only see the head; the rest of the constellation is visible from more southerly locations. Catch a glimpse in July of the bright red star Antares (The rival of Mars) on the stem of the `T` asterism low in the south.

In the southeast the constellation of Sagittarius (noted by the famous Teapot asterism) rises late evening. This area of sky is rich in star fields of the Milky Way and has many fine clusters but is only observable in our evening skies during the summer months. Looking  at Virgo we look outside our own Milky Way galaxy towards the external galaxies of the Virgo Cluster , look  to Sagittarius  to into the spiral arm of our own galaxy, the centre of our own galaxy is however too far south to see from the UK

The orange star Arcturus is found by following the curve of stars in the handle of the Plough down. The constellation of Bootes, resembles a `kite` or `Club ` in shape.   The star Izar is a beautiful orange/ blue double star visible in small telescopes. To the east of Bootes find the `horseshoe` shaped constellation of Corona Borealis (Northern Crown) and the `Keystone` Asterism in the constellation of Hercules. Hercules also has M13 the famous Globular Cluster, visible to the unaided eye as a misty patch; telescopes show the true wonder of this cluster with over 750,000 stars. Likewise another nice globular is M92 in Hercules.

Sky looking east at 10pm BST mid July  2017

July - East

In July, the summer constellations of Lyra and Cygnus are rising by mid evening, the Milky Way may be visible on moonless evenings from a dark site.  Stretching from low in the south east to low in the north west, this misty band is best seen with binoculars, follow the star fields from Altair, down through Scutum and into Sagittarius is stunning in a dark sky. If you are on holiday and visiting a dark sky site, remember to take a pair of binoculars with you.

Sky looking north at 10.30 pm BST mid July 2017

July - North

The Plough stands with its handle pointing upward follow the pointer’s Dubhe and Merek to find the polestar Polaris. The `W` shaped constellation of Cassiopeia is near to its lowest point in the north late evening.  The Milky Way follows the galactic equator and stretches from east through the constellations of Cygnus, Cassiopeia, Perseus and down into the northern horizon.  The bright star Capella is positioned almost due north and is circumpolar i.e. does not set from our latitude.

Sky looking west at 10 pm BST mid July 2017

July - West

Mercury very low in twilight   (Only look after Sunset) and on Saturday July 15th, Jupiter shines brightly low in the south western aspect. (Open public observing evening) , part of Bradgers Hill weekend – see LAS web site home page for details.

Comet C/2015 V2 Johnson continues to head southward but at 7.5m the bright evening twilight makes this low surface brightness object difficult to observe.

July - Jupiter Moon

WINJOPOS software prediction for telescopic view of Jupiter’s moons July 15th (as example)

Highlights of the Month

Saturn visible low in the south late evening, just past opposition shows nice ring detail, northern polar region. Titan is the brightest of Saturn’s moons which is visible in a small telescope and moves from evening to evening with respect to the planet, orbiting Saturn in just 15.9 days.

July - Saturn

WINJOPOS software prediction for telescopic view of Saturn’s moons July 15th (as example) .

LAS Finder chart for the star fields of Sagittarius and Scorpius low in the south late evening in July. Binoculars show the rich star fields and star clusters as well as star colour, observe from a dark site in moonless conditions in early July.

More detailed finder charts and newsletters are available to LAS members on the member’s page.

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