WHAT'S UP THIS MONTH - JUNE 2017
(Link to What's up - May 2017)
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THESE PAGES ARE INTENDED TO HELP YOU FIND YOUR WAY AROUND THE SKY
Click HERE for a downloadable PDF white chart - (Close PDF file to return here)
The chart above shows the whole night sky as it appears on 15th May at 22:00 (10 o'clock) in the evening British Summer Time (BST). As the Earth orbits the Sun and we look out into space each night the stars will appear to have moved across the sky by a small amount. Every month Earth moves one twelfth of its circuit around the Sun, this amounts to 30 degrees each month. There are about 30 days in each month so each night the stars appear to move about 1 degree. The sky will therefore appear the same as shown on the chart above at 11 o'clock BST at the beginning of the month and at 9 o'clock BST at the end of the month. The stars also appear to move 15º (360º divided by 24) each hour from east to west, due to the Earth rotating once every 24 hours. The sky appears to rotate from east to west around the Pole Star (Polaris).
The centre of the chart will be the position in the sky directly overhead, called the Zenith. First we need to find some familiar objects so we can get our bearings. The Pole Star Polaris can be easily found by first finding the familiar shape of the Great Bear ‘Ursa Major' that is also sometimes called the Plough or even the Big Dipper by the Americans. Ursa Major is visible throughout the year from Britain and is always quite easy to find. This month it is almost directly overhead. Look for the distinctive saucepan shape, four stars forming the bowl and three stars forming the handle. Follow an imaginary line, up from the two stars in the bowl furthest from the handle. These will point the way to Polaris which will be to the north of overhead at about 50º above the northern horizon. Polaris is the only moderately bright star in a fairly empty patch of sky. When you have found Polaris turn completely around and you will be facing south. To use this chart, position yourself looking south and hold the chart above your eyes.
Planets observable in the evening sky: Jupiter and Saturn with Venus visible in the morning before dawn.
EXPLORING THE NIGHT SKY THIS MONTH
The Southern Night Sky during June 2017 at 22:00 BST (9:00 pm)
The sky has been darkened to show the objects of interest more clearly
The chart above shows the night sky looking south at about 22:00 BST on 15th June. West is to the right and east to the left. The point in the sky directly overhead is known as the Zenith and is shown at the upper centre of the chart. The curved brown line across the sky at the bottom is the Ecliptic or Zodiac. This is the imaginary line along which the Sun, Moon and planets appear to move across the sky. The constellations through which the ecliptic passes are known as the constellations of the ‘Zodiac'.
Constellations through which the ecliptic passes this month are: Gemini (the Twins) but low in the north west, Cancer (the Crab) to the west of Leo, Leo (the Lion), Virgo (the Virgin), Libra (the Scales), Scorpius (the scorpion) and Sagittarius (the Archer) both just appearing over the south eastern horizon.
The Milky Way (our Galaxy) appears to rise up through Sagittarius on the south eastern horizon. It continues up through the constellations of Aquarius and Cygnus then off the top left of the chart.
Gemini is off the west the chart and disappearing over the western horizon. Leo (the Lion) is on the right of the chart with is distinctive ‘hook' shaped asterism looking like a sickle or a back to front question mark (?). The pattern that the brightest stars trace out is the very obvious shape of a resting lion or the Sphinx in Egypt. It is thought the Sphinx was carved into the shape of the lion from a similar looking natural rock formation in ancient times to represent the star formation of the lion, in the sky, on Earth. The original lion's head was replaced by the pharaoh's head we see today later during the reign of Pharaoh Khafre around 2558 to 2532 BC .
To the east (left) of Leo along the ecliptic is the constellation of Virgo (the Virgin). The constellation shape is comprised of mainly fairly faint stars except Spica which is easy to find. Jupiter is located in Virgo just above Spica so the bright planet can be used to locate Virgo. The constellation of Virgo was the Constellation of the month last month. Following Virgo and just above southern horizon is the rather indistinct constellation of Libra (the Scales).
Above and to the east of Virgo is the spring constellation of Bo?tes conspicuously identified by the bright red star Arcturus. The star pattern of Bo?tes looks like a traditional kite with Arcturus at the bottom where the tail would be attached. To the east of Bo?tes is the constellation Hercules, named after the hero from Greek mythology. Hercules is the constellation of the month.
To the east of Hercules is the famous ‘Summer Triangle' with the bright stars Deneb, Vega and Altar at the corners of the imaginary triangle. The name of this distinct summer sky feature was suggested by the late and great Sir Patrick Moore. The Summer Triangle is easy to find and a great place to start exploring the night sky. The most northerly star Deneb is bright and will be almost directly overhead later in the summer. Deneb is the brightest star in the constellation of Cygnus (the Swan). To the south west of Deneb is the even brighter star Vega in the small but interesting constellation of Lyra (the Lyre – small harp ). Altar the only bright star in the constellation of Aquila (the Eagle) has a fainter star to either side.
Almost overhead this month is the best known of all the constellations Ursa Major (the Great Bear) also known as the Plough or the Big Dipper to the Americans.
CONSTELLATION OF THE MONTH – HERCULES
The constellation of Hercules and the Summer Triangle
The chart above shows the constellation of Hercules and its location to the west of the Summer Triangle. Hercules has a distorted square made up of the four brightest stars at its centre. This distorted square of stars is called ‘the Keystone' because of it resemblance to the centre stone of an arch or bridge known as the ‘Keystone'. The ‘Keystone' asterism (shape) can be a little difficult to identify Ffor the first time in a light polluted sky but should be easier to find again the next time.
The jewel of Hercules is without doubt is the Great Globular Cluster, Messier 13 (M13). M13 can be found in the western vertical imaginary line of the ‘Keystone'. It is just visible using a good pair of 9 x 50 binoculars. The cluster of about a million stars can be seen using a 90mm f 10 telescope but will look very impressive when using a larger telescope. A 100mm to 150mm telescope using a magnification of about 150 will reveal the outer stars as individual stars.
Messier 13 (M13) t he Great Globular Cluster in Hercules
Globular clusters are thought to be the cores of small galaxies that have ventured too close to our Giant Spiral Galaxy (the Milky Way). They are the closely packed central stars of a small galaxy that were strongly held together by their mutual gravity while the loosely bound outer stars were stripped away by the powerful gravity of the Milky Way Galaxy. There are about 100 Globular Clusters surrounding our Galaxy but M13 is our closest and brightest.
POSSIBLY ONE OF OUR SUN's SISTERS HAS BEEN FOUND IN HERCULES
Like most stars, our Sun is believed to have been part of an open cluster comprised of a few tens to a few hundred stars. For at least the first few hundred million years, following their formation approximately 4.3 billion years ago, the stars would have been in an open cluster. In the time since its formation, the solar cluster has had ample time to dissipate. The members of the cluster will have gravitationally unbound themselves as they gradually moved apart. They then began their own long journeys around our Milky Way Galaxy.
A star known as HD 162826 (also known as HIP 87382) in the constellation of Hercules, 110 light-years away has been found to have an identical light spectrum to our Sun. This makes it very likely that it was formed in the same cluster as our Sun (it may be our Sun's sister). The spectrum of a star displays patterns of dark lines superimposed on the overall ‘rainbow' colours. There are many hundreds of these lines all made up from groups of distinct absorption lines where certain wavelengths of light have been absorbed by each element present in and around the star. The pattern of these lines is distinct for each star, rather like our DNA or fingerprints. Stars that form in the same nebula will have a very distinctly similar pattern of absorption lines revealing the proportions of all the elements present. Until about three years ago it was thought to be almost impossible that we would ever be able to find our Sun's siblings but we may have done just that. If it is proved that HD 162826 is our Sun's sister then this will an amazing find. The stars would have travelled on separate paths a number of times around our galaxy and have now returned to be just 110 light years apart.
The position of HD 162826 (HIP 87382)
Closer view of HD 162826 (HIP 87382)
JUPITER AND SATURN IN THE SUMMER
The locations of Jupiter and Saturn in the southern night sky
Jupiter has been in a perfect position for observing over the last few months and will still be around for the next three months. It rises over the eastern horizon in the early afternoon and is in the south west as the Sun sets. It is observable as soon as it is dark enough to locate and until it sets in the west at about 01:00.
The King of the Planets is located in the constellation of Virgo but is much brighter than any of the stars in its host constellation so is very easy to find. Except for the Moon it is by far the brightest object in the night sky. Its magnitude is -2.2 which is much brighter than the brightest star Sirius that has a magnitude of -1.4. Venus is brighter but it is a morning object at the moment rising just before the Sun. Jupiter's four brightest moons can be seen using binoculars. A modest telescope will show detail in the cloud bands and the Great Red Spot.
Jupiter with its four brightest moons on 22nd June
Saturn appears over the south eastern horizon at 20:30 in the beginning of this month and at 19:00 by the end of the month. It will be at its best and highest position above the horizon at around midnight. It will always be low and in the dirty turbulent air close the southern horizon.
A computer generated view of Saturn and its moons
A medium sized telescope will be required to see the ring system well and to be able to make out any of the features on the surface of the planet. Some of the moons will be visible in the telescope on a clear night. The largest moon Titan will be the easiest to see but up to 5 of the smaller moons may be visible depending on the telescope used and the prevailing condition of the sky.
Saturn is considerably more difficult to observe that Jupiter. This is because it is twice as far away from us and Saturn is and it is little smaller. Saturn receives only 25% of sunlight that Jupiter receives and we receive only 25% of reflected sunlight compared to Jupiter. It appears only half the size of Jupiter and because of the much reduced illumination Saturn appears only about 5% as bright as Jupiter.
THE PLANETS THIS MONTH
MERCURY will not be visible this month as it is too close to the Sun in the early morning sky.
Mercury and Venus in the early morning sky
VENUS is now making its appearance in the early morning sky before sunrise in the east at about 02:00. It will appear very bright and sparkling in the turbulent air close to the horizon. The sky in the computer generated chart above has been darkened to show Mercury and Venus.
MARS will be lost in the bright sky in the west as the Sun is setting and will not be visible.
JUPITER is now just past its best for observing and moving towards the eastern horizon. It will be observable in the south east as soon as it is dark and still looks magnificent when viewed using a telescope. It will set over the western horizon at about 02:00 in the beginning of the month and around midnight at the end of the month. A good pair of binoculars will reveal the four brightest of Jupiter's moons, Io, Europa, Ganymede and Callisto.
SATURN will be visible in the brightening dawn sky close to the south eastern horizon. The ringed planet rises at about 20:30 at the beginning of this month and by 19:00 at the end of the month. The ring will appear wide open and easy to see however the view of Saturn will not be very good as it is quite close to the horizon and in turbulent, dirty air. A medium sized telescope (100 to 150mm aperture and 150x magnification) will be required to see the rings well.
A computer generated view of Saturn and its moons
URANUS will still be too close to the Sun to be seen.
NEPTUNE will be very difficult to see.
The Sun rises at 03:40 at the beginning of the month and at 03:45 by the end of the month. It will be setting at 20:13 in the beginning and 20:25 at the end of the month. The Summer Solstice (midsummer / longest day) will be on 21 st June and will also be the shortest night of the year.
The chart below has been generated using Richard Fleet's brilliant ‘Graphdark' application. It shows graphically the availability of the solar system objects for observing. The band across the centre is the night time viewing window and the light blue area is daylight. The vertical lines on the night band are days through the period shown on the scale along the bottom. The side scales show the time with ‘0' at midnight, reading up to 10:00 and down to 14:00.
The coloured lines show when the planets can be seen and the white / blue / black bands represent the presence of the Moon. [White] Moon in the sky, [Black] moonless night and [Blue] no Moon but the summer sky is not completely dark because the Sun is only just over the northern horizon.
Sunspots and other activity on the Sun can be followed live and day to day by visiting the SOHO website at:
THE MOON PHASES IN JUNE
First Quarter will be on 1st June
Full Moon will be on 9th June
Last Quarter will be on 17th June
New Moon will be on 24th June.
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