WHAT'S UP THIS MONTH - OCTOBER 2020

(Link to What's Up September 2020)

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

The chart above shows the whole night sky as it appears on 15th October at 22:00 (10 o'clock) in the 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 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 in the North West. 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, Saturn, Neptune, Mars and Uranus.

Remember! British Summer Time (BST) ends at 02:00 on Sunday 25th October

 

EXPLORING THE NIGHT SKY THIS MONTH

The Southern Night Sky 15th October 2020 at 22:00 BST

The chart above shows the night sky looking south at about 22:00 BST on 15th October. West is to the right and east to the left. The point in the sky directly overhead is known as the Zenith or Nadir and is shown at the 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 brightest stars often appear to form a group or recognisable pattern; we call these ‘Constellations'.

Constellations through which the ecliptic passes this month are Sagittarius (the Archer), Capricornus (the Goat), Aquarius (the Water Carrier), Piscis (the Fishes), Aries (the Ram), Taurus (the Bull) and Gemini (the Twins just off the chart to the west (left)).

Just disappearing over the south western horizon is the constellation of Sagittarius (the Archer). It is really a southern constellation but we can see the upper part creep along the horizon during the summer. The central bulge of our galaxy is located in Sagittarius so the richest star fields can be found in the constellation along with many of the beautiful and interesting deep sky objects that we seek out ( labelled in yellow print).

The summer constellations are still prominent in the night sky lead by Hercules (the Hunter). Following Hercules is the Summer Triangle with its three corners marked by the bright stars: Deneb in the constellation of Cygnus, Vega in Lyra, and Altair in Aquila. The Summer Triangle is very prominent and can be used as the starting point to find our way around the night sky. The Milky Way (our Galaxy) flows through the Summer Triangle passing through Cygnus, down to the horizon in Sagittarius. The Milky Way flows north from the Summer Triangle through the rather indistinct constellation of Lacerta (the Lizard), past the pentagon shape of Cepheus and on through the ‘W' shape of Cassiopeia (a Queen).

All the Superior Planets (those orbiting the Sun outside Earth's orbit) are visible in the south during the night. Jupiter and Saturn are most prominent as Jupiter is very bright in the south with Saturn very close by. The Gas Giant Planets are followed across the sky by Neptune the most distant planet then the distinctly orange and bright Mars and completing the parade of planets is Uranus. The outermost planets Uranus and Neptune do really need a good pair of binoculars to find and a telescope to see as small blue discs.

Mars rises over the eastern horizon at about 20:30 BST (8:30 pm). It is bright at the moment and will continue getting brighter until on 13th October it will be at Opposition (in the south at midnight GMT) and at its brightest this year.

Planets observable: Jupiter, Saturn, Neptune, Mars, Uranus (in the evening) and Venus (in the early morning).

 

CONSTELLATIONS OF THE MONTH – PISCES AND ARIES

The constellations of Pisces (the Fishes) and Aries (the Ram)

The constellations of Pisces (the Fishes) and Aries (the Ram) are of special interest this month because they are hosts to the planets Mars and Uranus. See the chart above.

The constellations of Pisces (the Fishes) and Aries (the Ram) are not the easiest constellations to find as their stars are not very bright. However this year the presence of the planet Mars within the boundaries of Pisces will help in identifying these rather illusive constellations. Mars is very bright this month and cannot be missed in the southern sky.

Pisces is one of the twelve constellations of the Zodiac and appears as one of the birth signs. The Zodiac is called the Ecliptic by astronomers and is the imaginary line along which the Sun, Moon and planets appear to move across the sky. Pisces is preceded on the Ecliptic by Aquarius (the Water Carrier) to the west (right) and followed by Aries (the Ram) to the East) left.

Pisces and Aries showing its illustrations and borders

The easiest way to find Pisces is to find Mars then look above and to the west (right) to locate the Great Square of Pegasus (the Winged Horse). The Great Square of Pegasus is larger than may be expected but once the square is found it is much easier to find again.

The recognised asterism (pattern of stars) that represents the constellation of Pisces (the Fishes) does not, even with the best imagination, look anything like fishes. It is a meandering line of fairly faint stars that loop around the lower eastern (lower left) corner of the Square of Pegasus. It looks more like a sea serpent or an eel rather than any kind of fish. See the charts above.

So the constellations surrounding Pisces are Pegesus to the North West (above and to the right), Aquarius to the South West (lower right), Cetus (the Whale) to the South (below) and Aries (the Ram) to the East (left). Pisces does host one Messier deep space object known as Messier 74 (M74). This is a lovely Spiral Galaxy with very distinct curved spiral arms. This is difficult to see with a telescope but looks beautiful in images.

Aries (the Ram) is represented by a rather indistinct line of three stars and looks nothing like a Ram. Aries has no deep sky objects but is host to the outer planet Uranus this year. Uranus can just about be seen using a good pair of binoculars in a very dark and clear sky but does really need a telescope to see well.

Aries has no interesting objects but it is important for one ancient reason. The First Point of Aries is the location of the vernal equinox, used as a reference point in celestial coordinate systems. In diagrams using such coordinate systems, it is often indicated with the Astrological Zodiac sign of the Ram. It is one of the two points on the celestial sphere at which the celestial equator crosses the ecliptic, the other being the First Point of Libra, located exactly 180° from it.

Due to precession of the equinoxes since the position was originally named in antiquity, the position of the Sun on the spring (March) equinox is now in Pisces (but still called the First Point of Aries). The autumn (September) equinox is now in Virgo.

 

THE ORIONID METEOR SHOWER

The Radiant of the Orionid Meteor Shower

The Orionid Meteor shower occurs between 16th and 30th October but peaking on the evening and morning of the 20th and 21st October.

The chart above shows the night sky looking towards the eastern horizon at about midnight GMT (01:00 BST on 22nd October). The constellation of Orion is just rising over the eastern horizon and the radiant point of the Orionid Meteor Shower is shown arrowed. The paths of the meteors will appear to be emanating from the direction of the radiant point. The radiant point of the Orionid Meteor Shower is located to the east (left) of Orion's club as it is held above his head. See the chart above. Earlier in the evening any meteors will appear to originate from below the horizon. This means all the meteors will be moving up from the eastern horizon and in a ‘fan' shape across the sky.

To start viewing allow about five minutes for your eyes to become adapted to the dark. This period can be used to familiarise yourself with the sky and work out where everything is. Try to turn off all lights around you. If there is a street light bothering you, it may be possible to erect a screen around yourself using garden canes, step ladders, washing poles, string and old sheets, curtains, towels or even newspapers. Even lights which appeared dim when you first began your session seem to get very bright when your eyes are fully adjusted to the dark.

It is useful if you can observe from your own back garden because you can quickly get used to the positions of stars from one night to the next. It is not always possible to use your own garden due to the dazzling effect of street lights or perhaps trees or buildings blocking the view. It may be necessary therefore to go to a darker area away from lights. If this is the case it is much better to go with a friend, if possible, as it will be safer and more enjoyable.

A remote observing site also has the disadvantage of having to transport any equipment. If it is decided to try a remote site, always check the weather forecast first - this might save a lot of travelling and anguish when the sky clouds over shortly after all has been set up.

A garden ‘lounger' chair is an excellent piece of equipment especially the type that can be reclined into a near horizontal position. This will help avoid neck ache when looking up.

After making yourself warm and comfortable and allowing enough time for your eyes to become adapted to the dark it is time to start observing. The first thing to do is to look around the sky to find familiar objects. The most common thing used is the constellation of Ursa Major also called the Plough. Use the instructions on the back page to align the chart. Now position your star chart just above your eyes ensuring that the south position on the map is at the bottom. What you see represented on the chart should be what you see in the sky. Once the orientation is complete the chart can be lowered into a convenient reading position.

Observing can start before midnight but there will most likely be fewer meteors at this time. There are two reasons for this, first the radiant of the Orionid shower will be below the eastern horizon until just before midnight so fewer meteors will appear above the horizon. Secondly, after midnight Earth will be ploughing head on into the main meteor stream. It is normally best to look up at an angle of around 45° above the horizon and 30° to 90° right or left from the radiant point. It will also be useful to familiarise yourself with the positions of the constellations in the direction you are looking while you are waiting for the meteors.

The meteors are fragments of dust left by Halley's Comet when is melted as it passed close to the Sun.

 

THE INNER SOLAR SYSTEM - OCTOBER 2020

The mid month morning sky at 10:00 (in the morning) showing the positions Mercury and Venus

MERCURY will not be visible this month as it is in the bright morning sky. See the chart above (the sky has been darkened to allow the planets to be seen).

VENUS reached its greatest western elongation (at its furthest apparent distance from the Sun) on 14th August. It is still rising in the in the east before the Sun rises. It is now ‘gibbous' (wider than half Moon shaped see below).

It is moving back towards the Sun and will appear smaller but ‘fuller' as it moves into Superior Conjunction (behind the Sun) on 25th March 2021. After passing through Superior Conjunction Venus will reappear in the evening sky in the west after the Sun has set.

Through a telescope the view of Venus is rather bland and in may be considered to be a little boring to observe. However Venus does show phases like our Moon. It has its orbit inside the orbit of Earth so it is classified as an ‘Inferior' planet along with Mercury the closest planet to the Sun. When Venus is positioned between Earth and the Sun it looks larger and has phases up to ‘half moon' shaped. When positioned beyond the Sun it displays Gibbous phases (wider than ‘half moon) and looks smaller as it moves away from us.

Venus as it will appear on 5th October

After conjunction it first appeared close to the Sun and was round when viewed using a telescope. As it was be located on the other side of the Sun it was fully illuminated but become larger and crescent shaped as it moved out from the Sun and towards us.

Venus can be observed during the day in the sunlit sky but this must only be done with great care. A goto telescope would be best but setting circles can be used. The dust cap must only be removed when it is confirmed that the Sun is not in view through the telescope.

MARS rises in the east at about 18:00 and is looking large at about 22 arc-seconds. Earth is catching up with Mars on their orbits around the Sun. This is because Earth's orbit is inside the orbit of Mars and is consequently travelling faster. Earth will catch up and overtake Mars on 13 th October and this is called Opposition. At opposition Mars will be in direct line with Earth and the Sun as shown on the chart below.

Mars at Opposition on 13th October 2020

At opposition Mars will be at it its closest point to Earth on this orbit. It can be seen on the chart above that the orbit of Mars is quite eccentric. The closest and furthest points possible are marked on the orbit. This opposition brings the two planets quite close together so Mars will appear significantly larger than it would appear at the ‘furthest' conjunction point on its orbit. Mars will actually be at its very closest on 6 th October at 62.07 million km.

There is another bit of good news for this opposition. The Ecliptic will be high so Mars will also be in good stable air for viewing. For more information about Mars see the main theme article about Mars in the Beginners Magazine this month.

OBSERVING MARS

Hubble images with the main features on Mars labelled

The picture above shows the main features that may be identified on the surface of Mars labelled for identification. It must be pointed out that the view of mars as seen through the average amateur astronomer's telescope will not be as clear as those shown in pictures above. The very best view possible using ~200x magnification and a medium sized telescope (120mm) on a very still clear night is likely to be something like the image below.

A good image through the eyepiece of a small telescope

Before starting to observe Mars point the telescope towards a fairly distant object during the day, a chimney is a good target. Take note of the orientation of the image to see if it is upside down or back to front? This will help with identifying features on Mars. The images above are the right way up (north at the top). Conventionally astronomically images are shown upside down to conform to the way the planet or our Moon. However these days the images are often shown the right way up that is with North up.

The rotation period of Mars is almost 40 minutes longer than Earth's, at 24 hours, 39 minutes and 35 seconds. This means that features centrally located on Mars' disc appear 40 minutes later on each consecutive night. This rotation speed also means half of the surface of Mars can be seen over the course of one night's viewing. During December we have eighteen hours of darkness so plenty of time to watch Mars rotate through 12 hours of its 24.6 hour day. That is if the weather and the observer's persistence permit.

Imagine looking at Mars one night and seeing a dark feature at the centre of its disc (what's known as the Central Meridian of Mars). The following night at exactly the same time, that feature would appear slightly further west and take an extra 40 minutes to reach the central meridian once again. The night after that, viewing at the same time, the feature would take 80 minutes to reach the central meridian.

A telescope is needed to see Mars as a disc and the larger the telescope the more detail can be seen. The ‘seeing conditions' (the clarity and stability of our atmosphere) is a very important factor for having a good view. Use a low power eyepiece (25mm) to start observing Mars then use a higher power (magnification) eyepiece (10x) to have a good look. If the image looks good then a Barlow Lens can be used to effectively double the magnification of the 10mm eyepiece. As Mars gets larger, its surface detail should be easier to see (it will be at its very closest and largest on 6th October).

Mars imaged by Steve Harris on 13th September 2020

The image above was taken using a modified (shop bought) webcam from the Orion range through a larger 300mm aperture telescope with a long focal length of 3000mm. Smaller telescopes can be used and can produce good images. The darker features shown on this image can be seen using a 100mm aperture telescope with a focal length of about 1000mm and fitted with a 2x Barlow Lens to give an effective focal length of 2000mm. Mars will appear smaller in a 100mm telescope and appear in the eyepiece and appear similar to the previous image to the image above.

The bright southern polar cap should be quite easy to see even using a smaller telescope. The planet surface has areas of light and dark, representing deserts and exposed rock. These are known as Albedo features, areas that appear bright or dark due to the amount of light they reflect. The larger and darker an albedo feature is the easier it is to see through a telescope.

Probably the easiest feature to recognise is Syrtis Major shown on the right Hubble image above. This large triangular feature points to the North Pole of Mars as can be seen in the Hubble image so North is up. So try to identify this feature if it is in view. Between the southern boundary of Syrtis Major and the southern polar cap lies the Hellas Basin. This 2,300km diameter basin is one of the largest impact craters in the Solar System. Hellas can sometimes appear bright due to clouds that can form in the basin.

The Hubble images above can be used to identify features seen through our telescope or on photographic images that we have produced. HST images can be downloaded for the view we are expecting during the planned observing period.

 

THE OUTER SOLAR SYSTEM – OCTOBER 2020

 

The chart above shows the positions of the planets observable in the night sky this month. Jupiter and Saturn were both at Opposition in July, Jupiter on 14th July and Saturn on 20th July. Opposition was the exact time when Earth overtook (to be more precise ‘undertook') Jupiter and Saturn on their orbits around the Sun.

When the planets were at Opposition they were due south at midnight 01:00 BST (00.00 GMT) during the night of the dates shown in the previous paragraph. At these times the planets were at the centre of the night sky in the south and at their maximum altitude on the Ecliptic above the horizon. Earth was located in a direct line between Jupiter (or Saturn) with the Sun on the opposite side of Earth at midnight.

Jupiter at Opposition imaged by Steve Harris

So on these nights the two giant planets were at their very best but unfortunately the Ecliptic is at its lowest at midnight in the summer (and highest at midday).

Therefore Jupiter and Saturn were low in the sky and close to the southern horizon where the air was thickest and most turbulent therefore appeared very unsteady.

At opposition Jupiter was ‘in theory' at its best and brightest on 14th July but in reality it did not look any different. It always looks large and bright and will continue to look impressive for the rest of this year until it disappears over the western horizon around Christmas.

However it was a different matter for Saturn on 20th July. At 23:00 BST (22:00 GMT) for about two hours the rings brightened. This was the exact time of opposition and the sunlight was reflected directly back towards the Sun and Earth. At this point the ice particles in Saturn's ring did not cast shadows on other particles because the Sun and Earth were in perfect line. The particles in the ring appeared fully illuminated and reflected all the light back making the ring brighter this is called the Seeliger Effect .

The image below shows the Seeliger Effect with the ring brighter at the time of Opposition shown on the left and how the ring system normally appears on the right.

Images showing the Seeliger Effect

The ring really did actually appear noticeably brighter when viewed through a telescope this year and will still look very beautiful until December this year.

 

THE CLOSE CONJUNCTION OF JUPITER AND SATURN

 

Jupiter and Saturn in (a wide) conjunction 20th September 2020 image Steve Harris

The following article was published in the September What's Up and is repeated here.

This interesting event, involving Jupiter and Saturn, will develop and become even more interesting through the months from now until the end of this year. Jupiter and Saturn are located close together in the sky at the moment and this is what astronomers call a ‘Conjunction'. This is a term used when two (or more) objects appear to move close together in the sky. See the image above.

The two Gas Giant Planets have appeared close together in the sky all summer and will continue to move even closer together until the end of the year when they will be very close. The converging orbital paths of the planets are shown on the chart below.

Orbital paths of Jupiter and Saturn 21st December

The orbital paths of the planets are show as red for Jupiter and brown for Saturn. It can be seen on the chart above that the orbital paths a getting closer towards the end of the year as the planets move west.

Jupiter and Saturn will not be any closer to each other than they normally are and will still be moving around their established orbits. This conjunction is just a ‘line of sight' effect from our point of view on Earth. The two planets will actually be as far apart from each other as Earth is from Jupiter (about 750 million kilometres).

Jupiter is approaching Saturn as it is moving faster than Saturn along its orbital path and will overtake Saturn on 21 st December. From our point of view they will appear very close together so at this time the two planets will be at their closest conjunction.

Jupiter and Saturn at their closest conjunction

The chart above shows how the two planets and their moons will appear using a telescope around the 21st December. They should fit into the field of view of most small telescopes and some larger telescopes using a low power eyepiece.

Like all astronomical events the weather will need to be kind to us and we will need a clear view towards the western horizon. The conjunction will unfortunately also be in the still bright sky after sunset.

THE REST OF THE SOLAR SYSTEM OCTOBER 2020

The mid month sky at 22:00 showing the positions Uranus and Neptune

URANUS will not be easy to see this month as it will be close to the southern horizon. It will rise at about 18:30 and be visible for the rest of the night. It will require a clear view to the horizon and modest telescope to see.

Uranus will be in Opposition on 31st October so it will be at its best for observing on this evening, weather permitting. As described previously for the opposition of Mars, also in opposition this month, Uranus will be ‘under taken' by Earth moving faster along its smaller orbit. At midnight on 31st October Uranus will be due south and in a direct alignment with Earth and the Sun. This will be 12 o'clock as it will be winter time - Greenwich Mean Time (GMT).

NEPTUNE will rise at about 17:00 but will not be easy to observe this month as it and will be close to the south horizon and requires a larger telescope.

 

THE SUN

The Sun rises at about 07:00 at the beginning of the month and 06:40 at the end. It sets at 18:20 at the beginning of the month and 16:40 at the end. There have been no Sun Spots over the last couple of months but the Sun should be moving into its active phase soon so some Sun Spots may start to appear.

Sun Spots can the monitored using any telescope fitted with a proper ‘safe' Solar Filter. These can be bought from Astronomy Shops or can be made using special solar filter Mylar plastic film that can also be bought from astronomy shops. It can be an interesting branch of astronomy and easy to do. We can simply record the appearance of new sun spots. The spots can also be followed as they move across the Sun or they can be sketched or imaged through the telescope and kept as a detailed log of Solar activity.

Any activity on the Sun can also be followed live using the day to day images of the Sun in detail by visiting the very good SOHO website at: http://sohowww.nascom.nasa.gov/ .

 

THE MOON PHASES DURING OCTOBER

Diagram showing the illumination of the Moon

As the Moon orbits Earth about once a month the Sun illuminates different areas of the surface as we see it from our position on Earth. We call these different views ‘Phases'. See the preceding diagram and the phase chart below.

When the Moon is in the same direction as the Sun the side facing us is dark and we cannot see the Moon. As the Moon moves away from the Sun we see a thin slither of the illuminated side, we call this phase the ‘New Moon'. The Moon is of course not new it is the same 4.3 billion year old Moon. It is just emerging from ‘Conjunction' with the Sun.

A week later the western (right) half of the Moon will appear to be illuminated we call this phase ‘First Quarter'. It will be in the south as the Sun is setting in the west.

Two weeks after New Moon the Moon will be on the opposite side of Earth to the Sun in the east and the whole of the Moon will be illuminated so we call this phase ‘Full Moon'.

Three weeks after New Moon the eastern half of the Moon is illuminated we call this phase ‘Last (or Third) Quarter'. Here the opposite side to the First Quarter is illuminated as the Moon moves back towards the Sun. The Third Quarter Moon will not rise until after midnight and will be in the sky in daylight during the following morning.

There will be a Blue Moon this month.

This month there will be an extra Full Moon on 31st October this is sometimes referred to as a ‘Blue Moon'. The Moon will not appear blue, the term ‘Blue Moon' just refers to it being a second Full Moon in one month.

The Moon completes 12 full cycles of its phases in about 354 days – which is 11 days short of a calendar year. Every two and a half years or so the difference adds up to an extra, 13th full moon, occurring during the year and this relatively rare occurrence is sometimes referred to as a ‘Blue Moon'.

However, the precise origins of the term are uncertain. It was originally the name given to the third Full Moon of a season containing four full moons. A more modern interpretation for ‘Blue Moon' is now applied to a second full moon occurring within a single calendar month.

Full Moon will be on 1st October

Last Quarter will be on 10th October

New Moon will be on 16th October

First Quarter will be on 23rd October

Full (Blue) Moon will be on 31st October

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