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The Night Sky September 2019


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 60 illustrated articles.



Image of the Month

Curiosity

Curiosity at Teal Ridge
Image: NASA, JPL-Caltech,MSSS

This view from Mars Curiosity Rover was taken on June 18th 2019, seven years after landing.   Since Curiosity landed on August 6th 2012, it has travelled 12 km across the Martian Surface.   Its 3m apart tracks lead back towards Vera Rubin Ridge withe the rin of Gale Crater in the distance.

The image below shows Vera Rubin in 1974 analysing data from different parts of the galaxy M33 to ascertain its rotational properties.   She discovered that the outer parts of a galaxy rotated faster than one would expect leading to the concept of 'Dark Matter' whose additional gravitational effect would give rise to the observed galaxy's rotation curve.

Rubin

Highlights of the Month


September - observe Saturn.

Saturn
Saturn in the evening Sky

Saturn which reached opposition on the 9th of July, is now low (at an elevation of ~14 degrees) in the south as darkness falls lying above the 'teapot' of Sagittarius.   Held steady, binoculars should enable you to see Saturn's brightest moon, Titan, at magnitude 8.2.   A small telescope will show the rings with magnifications of x25 or more and one of 6-8 inches aperture with a magnification of ~x200 coupled with a night of good "seeing" (when the atmosphere is calm) will show Saturn and its beautiful ring system in its full glory.

As Saturn rotates quickly with a day of just 10 and a half hours, its equator bulges slightly and so it appears a little "squashed".   Like Jupiter, it does show belts but their colours are muted in comparison.

The thing that makes Saturn stand out is, of course, its ring system.   The two outermost rings, A and B, are separated by a gap called Cassini's Division which should be visible in a telescope of 4 or more inches aperture if seeing conditions are good.   Lying within the B ring, but far less bright and difficult to spot, is the C or Crepe Ring.

Due to the orientation of Saturn's rotation axis of 27 degrees with respect to the plane of the solar system, the orientation of the rings as seen by us changes as it orbits the Sun and twice each orbit they lie edge on to us and so can hardly be seen.   This last happened in 2009 and they are currently at an angle of 26 degrees to the line of sight.   The rings will continue to narrow until March 2025 when they will appear edge-on again.

See more of Damian Peach's images: Damian Peaches Website"




Saturn
Saturn imaged in April 2012 by Damian Peach



September: Look for the Great Red Spot on Jupiter

Great Red Spot
Observe the Great Red Spot
Image: NASA

This list gives some of the best evening times during September to observe the Great Red Spot which should then lie on the central meridian of the planet. The times are in BST.

1st   20:17         15th 21:53

3rd   21:55         20th 21:03

8th   21:05        22nd 22:42

10th 22:44         27th 21:52

13th 20:14         29th 23:31


September - Find the globular cluster in Hercules and spot the "Double-double" in Lyra

M13
Use binoculars to find the globular cluster M13 in Hercules and the "Double-double" in Lyra
Image: Stellarium/IM

There are two very nice objects to spot with binoculars in the south-western sky after dark this month.   Two thirds of the way up the right hand side of the 4 stars that make up the "keystone" in the constellation Hercules is M13, the best globular cluster visible in the northern sky.   The 15 minute exposure image on right was taken by the author using a 127 mm APO refractor and SBIG 8.3 megapixel CCD camera.

Just to the left of the bright star Vega in Lyra is the multiple star system Epsilon Lyrae often called the double-double.   With binoculars a binary star is seen but, when observed with a telescope, each of these two stars is revealed to be a double star - hence the name!

M13
M13 imaged by Ian Morison in May 2014



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

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

Later in the month is a good time to look high in the Southeast 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.   Visible times of the eclipse are (in UT): on the 12th at 23:43 and the 15th at 20:31.

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




September 5th to 9th - midnight: Find Neptune.

Neptune
Neptune in Aquarius.
Image: Stellarium/IM

These nights are a great time to find the blue planet Neptune as it is very close to the 4th magnitude star Phi Aquarii.   With a magnitude of 7.8, large binoculars or a small telescope will be required to spot it.   A medium aperture telescope will reveal Neptune's disk showing a hint of blue grey.   With such a telescope, you might also be able to spot its 14th magnitude Moon Triton.   On the night of the 5th/6th Neptune lies just 13 arc seconds from Phi Aquarii!

Neptune
Neptune and Triton close to Phi Aquarii.



September - evening: find the 'Coathanger'.

The Coathanger
Brocchi's Cluster or the Coathanger
Image: Stellarium/IM

Looking upwards after dark you should spot the three stars making up the 'Summer Triangle'.   The lowest is Altair in Aquilla, up to its right is Vega in Lyra and over to its left is Deneb in Cygnus.   With binoculars sweep upwards about one third of the way from Altair towards Vega.   You should spot a nice asterism, formally 'Brocchi's Cluster' but usually called the Coathanger.   It is formed of a straight line of six stars below which is a 'hook' of four stars.   A pretty object!



September 8th: Two Great Lunar Craters

20thJuly
Tycho and Copernicus: Ian Morison

Two great Lunar Craters: Tycho and Copernicus
This is a great night to observe two of the greatest craters on the Moon, Tycho and Copernicus, as the terminator is nearby.   Tycho is towards the bottom of Moon in a densely cratered area called the Southern Lunar Highlands.   It is a relatively young crater which is about 108 million years old.  It is interesting in that it is thought to have been formed by the impact of one of the remnents of an asteroid that gave rise to the asteroid Baptistina.   Another asteroid originating from the same breakup may well have caused the Chicxulub crater 65 million years ago.   It has a diameter of 85 km and is nearly 5 km deep.   At full Moon - seen in the image below - the rays of material that were ejected when it was formed can be see arcing across the surface.   Copernicus is about 800 million years old and lies in the eastern Oceanus Procellarum beyond the end of the Apennine Mountains.   It is 93 km wide and nearly 4 km deep and is a classic "terraced" crater.   Both can be seen with binoculars.

Tycho's Rays
Full Moon showing Tycho's rays: Ian Morison

















A Messier Object imaged with the Faulkes Telescope: Messier 1 - The Crab Nebula

Messier 1
The Crab Nebula, M1
Image:Nik Szymanik
Faulkes Telescope North.

The Crab Nebula, M16, imaged by Nik Szymanek.
This image was taken using the Faulkes Telescope North by Nik Szymanek - one of the UK's leading astro-photograpers.   The Crab nebula - the first entry in Charles Messier's catalogue - is the remnant of a supernovae that was seen to explode in the year 1054.   It is visible as the lower right of the pair of stars at the centre of the nebula and is a "neutron star" just 30km across but weighing more than our Sun!   Under the intense pressure of gravity, the protons and electrons fused to form neutrons and the compact object became stable as gravity was opposed by "neutron degeneracy pressure" - a quantum mechanical force.   It is now spinning just under 30 times a second and emitting two opposed beams of light and radio waves which pass across our location in space.   We thus detect very regular pulses and so objects like this are called pulsars.   At 8.4 magnitudes it is easily seen in a small telescopes under dark transparent skies appearing as a smudge of light which is a little underwhelming to see!

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
September 28th September 6th September 14th September 22rd

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, shining on the 1st at magnitude -2.2 and falling to -2 during the month, can be seen in the south as darkness falls.   As the month progresses, its angular size drops from 39 to 36 arc seconds.   Jupiter, in the southern part of Ophiuchus, ended its retrograde motion on the 11th of August and so is now moving away from Antares in Scorpius initially lying some 7 degrees up and to its left.   A highlight gives the times when the Great Red Spot faces the Earth.   Sadly it is heading towards the southernmost part of the ecliptic so, as it appears in the twilight, it will only have an elevation of ~13 degrees (from central UK). Happily, its elevation will only have dropped by a degree or so an hour later in full darkness.   With its low elevation, atmospheric dispersion will take its toll and an atmospheric dispersion corrector would greatly help to improve our views of the giant planet.



Saturn

Saturn
The planet Saturn. Cassini - Nasa

Saturn, crosses the meridian, so is highest in the sky, at around 9pm BST as September begins.   Then, its disk is ~17.6 arc seconds across and its rings - which are still nicely tilted from the line of sight - spanning some 41 arc seconds across.   By month's end it will be best seen at around 8 pm BST when lying just west of south.   During the month its brightness falls from magnitude +0.3 to +0.5 whilst its angular size falls to 16.9 arc seconds.   Sadly, now in Sagittarius and lying on the south-western side of the milky way, it is at the lowest point of the ecliptic and will only reach an elevation of ~14 degrees.   As with Jupiter, an atmospheric dispersion corrector will help improve our view.




Mercury

Mercury.
Messenger image of Mercury Nasa

Mercury, passes behind the Sun (Superior Conjunction) on the night of September 3rd/4th so 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 which passes behind the Sun (superior conjunction) on September 2nd, lies too close to the Sun to be visible.   We will have to wait until the end of October to spot it in the pre-dawn sky at the start of its next apparition.




Venus

Venus
Venus showing some cloud structure

Venus went through superior conjunction on the far side of the Sun on the 14th August.   By month's end it will set in the west south-west 30 minutes after sunset but will be very difficult to see due to the fact that the ecliptic is at a shallow angle to the horizon and so Venus will have a very low elevation.   Binoculars and a very low horizon will be needed, but please do not use them until after the Sun has set.

Radar Image of Venus
Radar image showing surface features











The Stars

The Evening September Sky

September Sky
The September Sky in the south - early Sept:~11pm, late Sept:~10pm

This map shows the constellations seen towards the south in late 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 and Perseus.

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