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« September 2020


The Night Sky October 2020


Compiled by Ian Morison




This page, updated monthly, will let you know some of the things that you can look out for in the night sky.  It lists the phases of the Moon, where you will see the naked-eye planets and describes some of the prominent constellations in the night sky during the month.


New(ish)

The author's: Astronomy Digest

which, over time, will provide useful and, I hope, interesting articles for all amateur astronomers.   A further aim is to update and add new material to link with the books recently published by Cambridge University Press and which are described on the home page of the digest.   It now includes over 80 illustrated articles.



Image of the Month

Cygnus Loop

Filaments of the Cygnus Loop
Image: HST, NASA, ESA. W.Blair and Leo Shatz.

This is an HST image of part or the Cygnus Loop otherwise known as the Veil Nebula.   The filamants are seen as hydrogen gas is excited due to a shock front moving upwards at a rate of 170 km/sec resulting from a supernova explosion around 20,000 years ago and lying at a distance of around 2,400 light years.   The diameter of the loop is about 130 light years across and spans an angular diameter of 6 full moons.

The image below right shows the complete loop.

Cygnus Loop
Stellarium

Highlights of the Month


October - a great month to view Mars.

Mars
Mars imaged by the Hubble Space telescope. NASA, ESA

  This is a great month to observe Mars which has its closest approach to Earth on October the 6th when it will lie 39 million miles from Earth and reaches opposition on the 13th so the highest in the south around 1am BST.   Wonderfully, at this opposition, Mars is far higher in the sky than at recent oppositions.   In Pisces, Mars, outshining even Jupiter, can be first seen rising at 8pm BST in the southeast as October begins.   It crosses the meridian at 2am BST on the 1st of the month and at 11pm GMT by month's end.   Its magnitude as October begins is -2.5, peaking to -2.6 around opposition and then fades to -2.2 by the end of the month.   Its angular size is just over 22 arc seconds for most of the month, dropping slightly to 20 arc seconds by month's end.   Reaching an elevation of ~43 degrees when due south as seen from the UK, amateur telescopes will enable one to see features, such as Syrtis Major, on its surface when the seeing conditions are good.   This is the best time to observe Mars until 2035!

During this opposition, Mar's southern hemisphere is tipped towards the Earth and so the South Polar Cap should be visible, though much of its frozen carbon dioxide will have vaporised during the Martian summer.   Though the North Polar Cap is beyond our view, one should be able to spot the haze of the North Polar Hood lying above the northern limb of the planet. At 24.6 hours long, the Martian day is similar to ours, so the surface details remain similar at the same time each night.   Mars takes 41 days to make an apparent rotation as seen from Earth.




October - Find Neptune

Neptune
Neptune at opposition on September 11th
Image: Stellarium/IM

This month Neptune is just pass opposition and so will be visible during much of the night.   It lies in Aquarius below one of the circlets in Pisces and shines at magnitude +7.8 having a 2.4 arc second disc so binoculars or a telescope will be needed to spot it under a dark sky.   I hope the charts will help you find it - not so difficult as it lies close to a nice grouping of stars.   Of course, a well aligned computerised telescope will take you right there but, unless the seeing is exceptional, I suspect that the dark bluish disk will not be that obvious.

October, evening: the Double Cluster and the 'Demon Star', Algol.

Algol
Algol and the Double Cluster.
Image: Stellarium/IM

This month is a good time to look high in the east towards the constellations of Cassiopea and Perseus.   Perseus contains two interesting objects; the Double Cluster between the two constellations and Algol the 'Demon Star'.   Algol in an eclipsing binary system as seen in the diagram below.   Normally the pair has a steady magnitude of 2.2 but every 2.86 days this briefly drops to magnitude 3.4.

Double Cluster
Double Cluster imaged by IM and the Algol Light Curve



October: find M31 - The Andromeda Galaxy - and perhaps M33 in Triangulum

M31
How to find M31
Image: Stellarium/IM

In the late evenings when the Moon is not prominent, the galaxy M31 in Andromeda will be visible high in the southeast. The chart provides two ways of finding it:

1) Find the square of Pegasus.  Start at the top left star of the square - Alpha Andromedae - and move two stars to the left and up a bit.  Then turn 90 degrees to the right, move up to one reasonably bright star and continue a similar distance in the same direction.  You should easily spot M31 with binoculars and, if there is a dark sky, you can even see it with your unaided eye.   The photons that are falling on your retina left Andromeda well over two million years ago!

2) You can also find M31 by following the "arrow" made by the three rightmost bright stars of Cassiopeia down to the lower right as shown on the chart.

Around new Moon (16th October) - and away from towns and cities - you may also be able to spot M33, the third largest galaxy after M31 and our own galaxy in our Local Group of galaxies.   It is a face on spiral and its surface brightness is pretty low so a dark, transparent sky will be needed to spot it using binoculars (8x40 or, preferably, 10x50).   Follow the two stars back from M31 and continue in the same direction sweeping slowly as you go.   It looks like a piece of tissue paper stuck on the sky just a bit brighter than the sky background.   Good Hunting!





October 2nd - 1 hour before sunrise - Venus and Regulus

Venus
Venus just half a degree from Regulus in Leo.
Image: Stellarium/IM

Before dawn on the 2nd of the month, if clear, one will spot Venus sining at magnitude -4.1 just half a degree to the upper right of Regulus, Alpha Leonis.

October 10th - before dawn: The third quarter Moon close to Pollux in Gemini.

Moon
The Moon in Gemini.
Image: Stellarium/IM

Before dawn on the 10th of October, the third quarter Moon will lie down to the right of Pollux in Gemini.

October 14th - before dawn : Venus and a very thin crescent Moon.

Venus
Venus and a thin crescent Moon.
Image: Stellarium/IM

Before dawn on the 14th, Venus will be seen should it be clear below a very thin waning crescent Moon.   One may well be able to spot 'Earthshine' the dark side of the Moon lit by light reflected form the Earth.

October 22nd - after sunset : Jupiter, Saturn and a waxing Moon

Jupiter
Venus and a waxing Moon.
Image: Stellarium/IM

After sunset on the 22nd, Jupiter will be seen above a waxing Moon, one day before first quarter with Saturn up to its left.

October 29th - evening : Mars and a near full Moon.

Mars
Venus and a thin crescent Moon.
Image: Stellarium/IM

During the evening of the 29th, Mars will lies above the waxing Moon just 2 days before full.

October 7th and 23rd evening: the Hyginus Rille

20thJuly
Hyginus Rille location: IM.

For some time a debate raged as to whether the craters on the Moon were caused by impacts or volcanic activity.   We now know that virtually all were caused by impact, but it is thought that the Hyginus crater that lies at the centre of the Hyginus Rille may well be volcanic in origin.   It is an 11 km wide rimless pit - in contrast to impact craters which have raised rims - and its close association with the rille of the same name associates it with internal lunar events.   It can quite easily be seen to be surrounded by dark material.   It is thought that an explosive release of dust and gas created a vacant space below so that the overlying surface collapsed into it so forming the crater.   On the evenings given above, the rille lies near the terminator.

Hyginus Rille
Hyginus Crater and Rille













M109 imaged with the Faulkes Telescope

M109
Messier 109
Image: Daniel Duggan
Faulkes Telescope North.

The Galaxy M109, imaged by Daniel Duggan.
This image was taken using the Faulkes Telescope North by Daniel Duggan - for some time a member of the Faulkes telescope team.   It shows the barred spiral galaxy M109 that lies at a distance of 83 million light years in the constellation of Ursa Major.   It is the brightest galaxy in the Ursa Major group of some 50 galaxies.   Our own Milky Way galaxy is now thought to be a barred spiral like M109.

Learn more about the Faulkes Telescopes and how schools can use them: Faulkes Telescope"












Observe the International Space Station

The International Space Station
The International Space Station and Jules Verne passing behind the Lovell Telescope on April 1st 2008.
Image by Andrew Greenwood

Use the link below to find when the space station will be visible in the next few days. In general, the space station can be seen either in the hour or so before dawn or the hour or so after sunset - this is because it is dark and yet the Sun is not too far below the horizon so that it can light up the space station. As the orbit only just gets up the the latitude of the UK it will usually be seen to the south, and is only visible for a minute or so at each sighting. Note that as it is in low-earth orbit the sighting details vary quite considerably across the UK. The NASA website linked to below gives details for several cities in the UK. (Across the world too for foreign visitors to this web page.)

Note: I observed the ISS three times recently and was amazed as to how bright it has become.

Find details of sighting possibilities from your location from: Location Index

See where the space station is now: Current Position


The Moon

3rd Quarter Moon
The Moon at 3rd Quarter. Image, by Ian Morison, taken with a 150mm Maksutov-Newtonian and Canon G7.
Just below the crator Plato seen near the top of the image is the mountain "Mons Piton".   It casts a long shadow across the maria from which one can calculate its height - about 6800ft or 2250m.
`
new moon first quarter full moon third quarter
October 16th October 23rd October 1st October 10th

Some Lunar Images by Ian Morison, Jodrell Bank Observatory: Lunar Images

A World Record Lunar Image

World record Lunar Image
The 9 day old Moon.

To mark International Year of Astronomy, a team of British astronomers have made the largest lunar image in history and gained a place in the Guinness Book of Records!   The whole image comprises 87.4 megapixels with a Moon diameter of 9,550 pixels.  The resolution of ~0.4 arc seconds allows details as small as 1km across to be discerned!   The superb quality of the image is shown by the detail below of Plato and the Alpine Valley.  Craterlets are seen on the floor of Plato and the rille along the centre of the Alpine valley is clearly visible.  The image quality is staggering! The team of Damian Peach, Pete lawrence, Dave Tyler, Bruce Kingsley, Nick Smith, Nick Howes, Trevor Little, David Mason, Mark and Lee Irvine with technical support from Ninian Boyle captured the video sequences from which 288 individual mozaic panes were produced.   These were then stitched together to form the lunar image.

Plato and the Alpine valley
Plato and the Alpine Valley.

Please follow the link to the Lunar World Record website and it would be really great if you could donate to Sir Patrick Moore's chosen charity to either download a full resolution image or purchase a print.









The 8 day old Moon

Lunar Image
The 8 day old Moon imaged by Ian Morison.

This image was taken by the author on a night in March 2018 when the Moon was at an elevation of ~52 degrees and the seeing was excellent.   This enabled the resolution of the image to be largely determined by the resolution of the 200 mm aperture telescope and the 3.75 micron pixel size of the Point Grey Chameleon 1.3 megapixel video camera.   The use of a near infrared filter allowed imaging to take place before it was dark and also reduced the effects of atmospheric turbulence.   The 'Drizzle' technique developed by the Hubble Space Telescope Institute (HSTI) was used to reduce the effective size of the camera's pixels to allow the image to be well sampled.   Around 100 gigabytes of data, acquired over a 2 hour period, was processed to produce images of 54 overlapping areas of the Moon which were then combined to give the full lunar disk in the free 'stitching' program Microsoft ICE.   A further HSTI development called 'deconvolution sharpening' was then applied to the image.   The Moon's disk is ~6,900 pixels in height and has a resolution of 0.6 to 0.7 arc seconds.   Interestingly, as seen in the inset image, the rille lying along the centre of the Alpine Valley is just discernable and this is only ~0.5 km wide!   [Due to size limitations the large image is 2/3 full size.]









The Planets

 A montage of the Solar System
A montage of the Solar System. JPL / Nasa

Jupiter

Jupiter
A Cassini image of Jupiter . Nasa

Jupiter is now visible, low in the sky, just west of south when darkness falls as October begins and sets around 10:30 pm BST.   Towards the end of the month it will be seen towards the southwest after sunset and sets by ~08:30 pm GMT.   Its magnitude dims slightly from -2.4 to -2.2 during the month whilst its angular diameter falls from 40.5 to 37.1 arc seconds.   Sadly, even when first seen after sunset, it will only have an elevation of ~14 degrees above the horizon so the atmosphere will limit our views.   Due its position in the most southerly part of the ecliptic this has been a very poor opposition for those of us in the northern hemisphere.



Saturn

Saturn
The planet Saturn. Cassini - Nasa

Saturn. Following Jupiter into the sky, some 8 degrees behind at the start of the month but reducing to 5.2 degrees by Halloween, Saturn is best seen in the south just after sunset on the 1st.   Its magnitude drops slightly during the month from +0.5 to +0.6 whilst its angular size decreases from 17.2 to 16.4 arc seconds.   The rings span some 35 arc seconds across and, at ~22 degrees to the line of sight, show up well.   Saturn lies in Sagittarius near the border of Capricornus.   Saturn halted its retrograde motion on the 29th of September and, as the year progresses becomes closer to Jupiter until, on the 21st December they are just 0.1 degrees apart.   Sadly again, its low elevation of ~16 degrees when crossing the meridian will somewhat limit our views of this most beautiful planet.




Mercury

Mercury.
Messenger image of Mercury Nasa

Mercury passes in front of the Sun on the 25th of the month (inferior conjunction) and will not be visible this month.






Mars

Mars showing Syrtis major.
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa

Mars: See highlight above.




Venus

Venus
Venus showing some cloud structure

Venus, was at greatest elongation east back on August 12th but still dominates the pre-dawn sky rising around three hours before sunrise as October begins and a little less by month's end.   It shines at magnitude -4.1 as October begins, lying some half a degree from Regulus in Leo, dropping to -4 by month's end whilst its angular size shrinks from 15.5 to 13.2 arc seconds.   During the same time its its phase (the illuminated percentage of the disk) increases from 72% to 81% which is why the fall in magnitude is so small.   It still reaches an elevation of ~32 degrees at sunrise.   Venus entered the constellation of Leo on the 23rd of September and moves into Virgo on the 23rd of the month.

Radar Image of Venus
Radar image showing surface features









The Stars

The Evening October Sky

October Sky
The October Sky in the south - mid evening

This map shows the constellations seen towards the south in mid evening. To the south in early evening - moving over to the west as the night progresses is the beautiful region of the Milky Way containing both Cygnus and Lyra. Below is Aquilla. The three bright stars Deneb (in Cygnus), Vega (in Lyra) and Altair (in Aquila) make up the "Summer Triangle". East of Cygnus is the great square of Pegasus - adjacent to Andromeda in which lies M31, the Andromeda Nebula. To the north lies "w" shaped Cassiopeia with Perseus below.

The constellations Lyra and Cygnus

Cygnus and Lyra
Lyra and Cygnus

This month the constellations Lyra and Cygnus are seen almost overhead as darkness falls with their bright stars Vega, in Lyra, and Deneb, in Cygnus, making up the "summer triangle" of bright stars with Altair in the constellation Aquila below. (see sky chart above)

Lyra

Lyra is dominated by its brightest star Vega, the fifth brightest star in the sky. It is a blue-white star having a magnitude of 0.03, and lies 26 light years away. It weighs three times more than the Sun and is about 50 times brighter. It is thus burning up its nuclear fuel at a greater rate than the Sun and so will shine for a correspondingly shorter time. Vega is much younger than the Sun, perhaps only a few hundred million years old, and is surrounded by a cold,dark disc of dust in which an embryonic solar system is being formed!

There is a lovely double star called Epsilon Lyrae up and to the left of Vega. A pair of binoculars will show them up easily - you might even see them both with your unaided eye. In fact a telescope, provided the atmosphere is calm, shows that each of the two stars that you can see is a double star as well so it is called the double double!

The Double Double
Epsilon Lyra - The Double Double

Between Beta and Gamma Lyra lies a beautiful object called the Ring Nebula. It is the 57th object in the Messier Catalogue and so is also called M57. Such objects are called planetary nebulae as in a telescope they show a disc, rather like a planet. But in fact they are the remnants of stars, similar to our Sun, that have come to the end of their life and have blown off a shell of dust and gas around them. The Ring Nebula looks like a greenish smoke ring in a small telescope, but is not as impressive as it is shown in photographs in which you can also see the faint central "white dwarf" star which is the core of the original star which has collapsed down to about the size of the Earth. Still very hot this shines with a blue-white colour, but is cooling down and will eventually become dark and invisible - a "black dwarf"! Do click on the image below to see the large version - its wonderful!

M57 - The Ring Nebula
M57 - the Ring Nebula
Image: Hubble Space telescope

M56 is an 8th magnitude Globular Cluster visible in binoculars roughly half way between Alberio (the head of the Swan) and Gamma Lyrae. It is 33,000 light years away and has a diameter of about 60 light years. It was first seen by Charles Messier in 1779 and became the 56th entry into his catalogue.

M56 - Globular Cluster
M56 - Globular Cluster

Cygnus

Cygnus, the Swan, is sometimes called the "Northern Cross" as it has a distinctive cross shape, but we normally think of it as a flying Swan. Deneb,the arabic word for "tail", is a 1.3 magnitude star which marks the tail of the swan. It is nearly 2000 light years away and appears so bright only because it gives out around 80,000 times as much light as our Sun. In fact if Deneb where as close as the brightest star in the northern sky, Sirius, it would appear as brilliant as the half moon and the sky would never be really dark when it was above the horizon!

The star, Albireo, which marks the head of the Swan is much fainter, but a beautiful sight in a small telescope. This shows that Albireo is made of two stars, amber and blue-green, which provide a wonderful colour contrast. With magnitudes 3.1 and 5.1 they are regarded as the most beautiful double star that can be seen in the sky.

Alberio
Alberio: Diagram showing the colours and relative brightnesses

Cygnus lies along the line of the Milky Way, the disk of our own Galaxy, and provides a wealth of stars and clusters to observe. Just to the left of the line joining Deneb and Sadr, the star at the centre of the outstretched wings, you may, under very clear dark skys, see a region which is darker than the surroundings. This is called the Cygnus Rift and is caused by the obscuration of light from distant stars by a lane of dust in our local spiral arm. the dust comes from elements such as carbon which have been built up in stars and ejected into space in explosions that give rise to objects such as the planetary nebula M57 described above.

There is a beautiful region of nebulosity up and to the left of Deneb which is visible with binoculars in a very dark and clear sky. Photographs show an outline that looks like North America - hence its name the North America Nebula. Just to its right is a less bright region that looks like a Pelican, with a long beak and dark eye, so not surprisingly this is called the Pelican Nebula. The photograph below shows them well.

The North American Nebula
The North American Nebula

Brocchi's Cluster An easy object to spot with binoculars in Gygnus is "Brocchi's Cluster", often called "The Coathanger",although it appears upside down in the sky! Follow down the neck of the swan to the star Alberio, then sweep down and to its lower left. You should easily spot it against the dark dust lane behind.

The Coathanger
Brocchi's Cluster - The Coathanger

The constellations Pegasus and Andromeda

Pegasus and Andromeda
Pegasus and Andromeda

Pegasus

The Square of Pegasus is in the south during the evening and forms the body of the winged horse. The square is marked by 4 stars of 2nd and 3rd magnitude, with the top left hand one actually forming part of the constellation Andromeda. The sides of the square are almost 15 degrees across, about the width of a clentched fist, but it contains few stars visibe to the naked eye. If you can see 5 then you know that the sky is both dark and transparent! Three stars drop down to the right of the bottom right hand corner of the square marked by Alpha Pegasi, Markab. A brighter star Epsilon Pegasi is then a little up to the right, at 2nd magnitude the brightest star in this part of the sky. A little further up and to the right is the Globular Cluster M15. It is just too faint to be seen with the naked eye, but binoculars show it clearly as a fuzzy patch of light just to the right of a 6th magnitude star.

Andromeda

The stars of Andromeda arc up and to the left of the top left star of the square, Sirra or Alpha Andromedae. The most dramatic object in this constellation is M31, the Andromeda Nebula. It is a great spiral galaxy, similar to, but somewhat larger than, our galaxy and lies about 2.5 million light years from us. It can be seen with the naked eye as a faint elliptical glow as long as the sky is reasonably clear and dark. Move up and to the left two stars from Sirra, these are Pi amd Mu Andromedae. Then move your view through a rightangle to the right of Mu by about one field of view of a pair of binoculars and you should be able to see it easily. M31 contains about twice as many stars as our own galaxy, the Milky Way, and together they are the two largest members of our own Local Group of about 3 dozen galaxies.

M 31 - The Andromeda Nebula
M31 - The Andromeda Nebula

M33 in Triangulum

If, using something like 8 by 40 binoculars, you have seen M31 as described above, it might well be worth searching for M33 in Triangulum. Triangulum is

the small faint constellation just below Andromeda. Start on M31, drop down to Mu Andromedae and keep on going in the same direction by the same distance as you have moved from M31 to Mu Andromedae. Under excellent seeing conditions (ie., very dark and clear skies) you should be able to see what looks like a little piece of tissue paper stuck on the sky or a faint cloud. It appears to have uniform brightness and shows no structure. The shape is irregular in outline - by no means oval in shape and covers an area about twice the size of the Moon. It is said that it is just visible to the unaided eye, so it the most distant object in the Universe that the eye can see. The distance is now thought to be 3.0 Million light years - just greater than that of M31.

M33
M33 in triangulum - David Malin