WHAT'S UP THIS MONTH - MAY 2017

(Link to What's up - April 2017)

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THESE PAGES ARE INTENDED TO HELP YOU FIND YOUR WAY AROUND THE SKY

Click HERE for a downloadable white chart

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 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.

Planet observable in the evening sky: Jupiter. Saturn and Venus are visible in the morning before dawn.

EXPLORING THE NIGHT SKY THIS MONTH

The Southern Night Sky during April 2017 at 21:00 BST (9:00 pm)

The chart above shows the night sky looking south at about 22:00 BST on 15th May. 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: Taurus (the Bull) but low in the west, Gemini (the Twins), Cancer (the Crab), Leo (the Lion), Virgo (the Virgin), Libra (the Scales) and Scorpius (the scorpion) just appearing over the south eastern horizon.

The Milky Way (our Galaxy) appears to rise up from the south western horizon. It continues up through the constellations of Monoceros and Gemini then off the right of the chart.

The winter constellation of Orion and the winter constellations have all but set over the western horizon. The constellation of Gemini (the Twins) is easy to find by looking for the twin stars Pollux and Castor. There is a lovely Messier Open Cluster M35 in Gemini just off the end of the line of stars emanating from the bright star Castor. Castor is a double star when seen in a telescope with a third more distant companion nearby.

To the east of Gemini is the faint and rather indistinct constellation of Cancer (the Crab). The asterism (shape) of Cancer looks quite uninteresting but the Open Cluster Messier 44 (M44) Praesepe or the Beehive Cluster looks beautiful and like a swarm of bees around an old style hive when seen using binoculars.

Following Cancer is Leo (the Lion) 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 replace by the pharaoh's head we see today later during the reign of Pharaoh Khafre 2558 to 2532 BC.

To the east of Cancer 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 is the Constellation of the month last month. Just rising over the eastern horizon is the constellation of Libra (the Scales).

Above and to the east of Virgo is the spring constellation of Boötes conspicuously identified by the bright red star Arcturus. The star pattern of Boötes 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.

Directly 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. The main asterism (shape) actually looks most like a saucepan. The star half way along the saucepan handle is called Mizar and is a naked eye double star. The companion star to Mizar is called Alcor and is just visible to most people but can be easily seen using binoculars.

1st CONSTELLATION OF THE MONTH – BOÖTIS (the Herdsman)

The constellation of Boötis (the Herdsman)

The constellation of Boötis (the Herdsman) does not contain any bright deep sky objects but it is a very useful constellation to help find our way around the night sky. This is because its (only) bright star Arcturus is a beautiful bright Red Giant. The asterism (pattern or shape), formed by the other less bright stars, appears to look like a traditional ‘diamond' shaped kite. Arcturus is conveniently located at the lower point of the ‘kite' where the tail would be attached.

Although Arcturus is bright and distinctly orange in colour it can be conclusively identified by following a simple idiom phrase ‘Arc Down [from Ursa Major] to Arcturus'. This simply means: follow an arc down from the handle of the saucepan shape of Ursa Major (the Plough) to Arctaurus, as shown on the chart above.

Arcturus also designated as Alpha ( a) Boötis , is the brightest star in the constellation of Boötes and the fourth-brightest in the night sky also the brightest in the northern celestial hemisphere. Together with Spica and Denebola (or Regulus, depending on the source) Arcturus is part of the Spring Triangle.

Arcturus is relatively close at 36.7 light-years from the Sun and is a Red Giant of spectral type K0III. This is an ageing star around 7.1 billion years old that has used up most of its hydrogen fuel supply. It is 1.08 ± 0.06 times the mass of our Sun but has expanded to about 25 its diameter and is around 170 times more luminous. It therefore gives us an insight of what our Sun will be like when it becomes a Red Giant in about 4 billion years time.

Arcturus is a beautiful sight when seen using binoculars or a telescope. If the image is put slightly out of focus the orange colour becomes much more apparent.

A photographic image of Arcturus

2nd CONSTELLATION OF THE MONTH – CANES VENATICI (the Hunting Dogs)

The constellation of Canes Venatici (the Hunting Dogs)

Canes Venatici is a rather indistinct constellation with no bright stars and no obvious pattern of stars. However this constellation is very easy to find because it is located next to Ursa Major (the Great Bear) in fact it is directly below the ‘handle' of the saucepan shape of Ursa Major. See the chart on the previous page.

Although Canes Venatici is not very interesting to look at using our naked eye or binoculars it does have some very interesting deep sky objects to search out. There are four very nice galaxies and a beautiful Globular Cluster.

The most interesting of the galaxies is Messier 51 (M51) the Whirlpool Galaxy. This is in fact two galaxies that have been involved in a collision.

Messier 51 (M51) the Whirlpool Galaxy

The image above shows M51 in great detail and clearly shows how the smaller galaxy on the right has swept past the larger one and pulled off a trailing arm of stars and gas.

This galaxy was the first to be determined as an object outside of our galaxy. The discovery that this galaxy was not in our galaxy, resulted in the realisation that the universe was much bigger than was hither to believed and our galaxy was not the whole universe. It does require a larger telescope and a dark sky to see M51. The pattern of the spiral arms can be seen in a 200mm telescope but the sky does need to be dark and unpolluted by street lights.

Messier 63 (M63) is a spectacular spiral galaxy also known as the Sunflower Galaxy. It was one of the first galaxies found to have spiral arms. The spiral arms of M63 are particularly tightly wound. The contrast of the image below has been increased to show an arc of stars to the upper left that appear to have been pulled away in a close encounter with another galaxy at some time in its past.

Messier 63 (M63) the Sunflower Galaxy

Messier 94 (also known as the Cat's Eye Galaxy) is unusual because it has both an inner ring and an outer ring of spiral arms. These rings appear to form at resonance locations within the disk of the galaxy. The inner ring is the site of strong star formation activity and is sometimes referred to as a starburst ring. This star formation is fueled by gas that is dynamically driven into the ring by the inner oval-shaped bar-like structure.

Messier 94 (M94) a beautiful spiral galaxy

Messier 106 is an intermediate size spiral galaxy in the constellation Canes Venatici and located at a distance of about 22 to 25 million light-years away from Earth. It is also. It is suspected that part of the galaxy is falling into a super-massive black hole in the centre and is also classified as a Seyfert II type galaxy due to the X-rays and unusual emission lines detected.

Messier 106 (M106) a medium sized Spiral Galaxy

Messier 3 (M3) is a lovely Globular containing around 500,000 stars and is estimated to be 8 billion years old. It is located at a distance of about 33,900 light-years away from Earth and can be seen using a moderate sized telescope. A Globular Cluster is thought to be the dense core of a smaller galaxy that has ventured too close to a large galaxy and had its outer stars striped away by the enormous gravity. There are about 100 Globular Clusters orbiting in a halo that surrounds our galaxy the Milky Way. M3 can be seen using a small telescope and a larger telescope will reveal the out regions of M3 as individual stars.

Messier 3 (M3) a Globular Cluster in Canes Venatici

 

THE PLANETS THIS MONTH

MERCURY will not be visible this month.

VENUS has disappeared out of the evening sky but is now making its appearance in the early morning sky before sunrise in the east at about 03:00. It will appear very bright and sparkling in the turbulent air close to the horizon.

MARS will be lost in the bright sky in the west as the Sun is setting and will not be visible.

JUPITER is now at its very best for observing. It rises over the eastern horizon at 15:30 so will be observable in the south east as soon as it is dark. See the chart on page 7. A good pair of binoculars will reveal the four brightest of Jupiter's moons, Io, Europa, Ganymede and Callisto. The table below shows the times for moon transits and Shadow Transits of Jupiter this month. (The best views are shown in blue.)

 

 

Moon

Moon shadow

Date

Moon

Start

End

Start

End

4

Eur

19:47

22:12

21:02

23:29

4/5

Io

23:28

01:39

00:05

02:16

6

Io

17:54

20:05

18:33

20:44

11/12

Eur

22:07

00:33

23:39

02:05

13

Io

19:41

21:51

20:27

22:38

20/21

Io

21:28

23:39

22:22

00:32

27/28

Gan

18:15

20:39

22:22

00:40

27/28

Io

23:16

01:27

00:16

02:26

29

Eur

16:04

18:32

18:12

20:37

29

Io

17:44

19:54

18:45

20:55

Eclipses occur when a moon casts its shadow on to Jupiter. It is quite easy to see because the eclipse shadow looks like a black full stop on the planet. Moons can also be eclipsed as they pass through the very large shadow cast by Jupiter.

Transits occur when a moon passes in front of Jupiter. The moon is actually very difficult to see while it is in front of the planet as it is lost in the glare from the surface.

Occultations occur when a moon passes behind the planet.

Occultations and Transits are easy to follow with a telescope as the moon approaches Jupiter.

 

SATURN will be visible in the brightening dawn sky close to the south eastern horizon. The ringed planet rises at about 23:00 at the beginning of this month and by 21:20 at the end of the month. The ring will appear wide open and easy to see however the view of Saturn will not be good as it is quite close to the horizon and in turbulent, dirty air. It is observable in the south east from about 01:00 until the sky begins to brighten before sunrise. A medium sized telescope (100 to 150mm aperture and 150x magnification) will be required to see the rings well.

Although the rings are permanent, at least in terms of our lifetime, they do appear and disappear over a periods of about 7½ years. This is because we on Earth view the rings from different angles as we and Saturn orbit the Sun.

Saturn is approximately ten times further out from the Sun than Earth therefore we always see Saturn fully illuminated and never see phases. However we do see the rings from a different aspect over the course of Saturn's 29.46 (Earth) years orbit around the Sun. As Saturn is so far away from us and we are a lot closer to the Sun, we view Saturn almost as if we are at the same position as the Sun. Saturn has a 27.6° tilt but is always tilted in the same direction as it orbits the Sun. Therefore as we look out from our position, close to the Sun, Saturn's ring appears to tilt up and down as Saturn orbit s the Sun every 29.46 years . In 2003 we were looking at Saturn when it was tilted with its south pole towards us. (Shown at the extreme left position in the diagram below). We were therefore able to see the ring system tilted away from us. In this position we could see the underside of the rings that appeared wide open.

After 7½ years Saturn w ould have completed approximately a quarter of its ~30 year long orbit around the Sun and was at the lower position shown in the diagram above. Therefore in 2009 we were looking at Saturn side on. As the rings are very thin they disappear ed almost completely for a few months. Over the next 7½ years the rings gradually appeared to open out again until this year ( 2017 ) we will see the top surface tilted towards us as show in the position at the right of the diagram. The closing sequence will then continue until 2025 when we will again view the rings side on as shown at the top position in the diagram. Eventually in 2032 Saturn will return the same position it was in 2003 where the rings will be tilted away from Earth and wide open again.

As the rings are tilted towards us this year, they will appear to be wide open and very impressive. Even in a small telescope (100mm aperture) will show the ring system very well.

 

Saturn in the south on 20th May at 03:00 (3 o'clock)

URANUS will still be too close to the Sun to be seen.

NEPTUNE rises in the east at 02:00 so will, in theory, be observable before the Sun rises. However it will be close to the south eastern horizon and very difficult to see.

THE SUN

There are still occasional sunspots to see even though the active phase of the Solar Cycle is all but over.

The Sun rises at 04:30 at the beginning of the month and at 04:00 by the end of the month. It will be setting at 19:35 at the beginning and 20:00 at the end of the month. Sunspots and other activity on the Sun can be followed live and day to day by visiting the SOHO website at :

http://sohowww.nascom.nasa.gov/ .

 

THE MOON PHASES IN MAY

First Quarter will be on 3rd May

Full Moon will be on 10th May

Last Quarter will be on 19th May

New Moon will be on 25th May

It is possible to take pictures of the Moon with basic equipment or even just a DSLR camera. Some people have even taken pictures through the eyepiece of a small telescope using a compact camera or a mobile phone. It is even possible to take a reasonable image using a hand held DSLR.

The image below was taken by Pat Gamalatge from her garden in Newbury using her new Nikon Coolpix P900 DSLR that was just hand held. This camera does have a very high zoom capacity and a special Moon scene setting so is ideal for ‘snapping' the Moon.

The Moon imaged by Pat Gamalatge using her DSLR

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