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CURRENT MOON

Saturn

Saturn can be seen low in the southwest during twilight this month dropping down towards the horizon a little more each week. Shining at magnitude +0.5, it sets around 2 hours after the Sun on the 1st but little more than one hour by month end. It starts the month moving slowly eastwards in Ophiuchus but reaches the boundary of Sagittarius on the 18th. Last month, Saturn's rings reach their maximum tilt to the line of sight of 27 degrees and it is a real pity that Saturn is so low in the sky. Sadly, this will not improve for quite a few years as Saturn moves slowly through the lowest part of the ecliptic. Towards the end of the month Saturn edges closer to Mercury but, with both so low above the horizon after sunset, the pair will be difficult to spot.

Jupiter

Jupiter passed behind the Sun on October 26th and so will become visible again in the pre-dawn sky after the first week or so November. It will then lie down to the lower left of Venus. However, by the end of November it will rise some two hours before the Sun allowing its 31 arc second disk, shining at a magnitude of -1.7, to be observed under clear skies. The low elevation will, of course, hinder our view.

Mars

Mars , lying in Virgo, is now a morning object at the start of its new apparition and rises three to four hours earlier than the Sun. During the month, Mars has a magnitude of 1.7 and an angular size of just 3.9 (increasing to 4.2) arc seconds so no details will be seen on its salmon-pink surface. On the 4th, Mars is just three degrees to the upper right of Porrima, Gamma Virginis. This closes to two degrees by the 6th whilst, at the end of the month, it will lie just 3 degrees to the upper left of Spica, Alpha Virginis.

Venus

Venus, now moving back towards the Sun, rises some 90 minutes before dawn at the start of the month but this falls to 45 minutes by month's end. Its magnitude remains at -3.9 during the month as its angular diameter shrinks from 10.4 to 10 arc seconds. However, at the same time, its illuminated phase increases from 96% to 99% - which explains why its magnitude does not change. At the beginning of the month, it lies close to Spica, Alpha Virginis, with Venus some 100 times (5 magnitudes) brighter than Spica. By month's end, binoculars might well be needed to spot it low above the eastern horizon. But please do not use them after the Sun has risen.

Mercury

Mercury passed between us and the Sun (Superior conjunction) on October 8th and will become visible again after sunset in the latter part of the month. From around the 17th, it might be glimpsed with binoculars low in the southwest 20 minutes after sunset shining at magnitude -0.4. It reaches greatest elongation, 22 degrees east of the Sun, on November 23rd but, due to the shallow angle of the ecliptic to the horizon, never lies far above the horizon. In the last few days of the month its magnitude falls to -0.2 and it only lies ~5 degrees above the horizon 30 minutes after sunset.

The Night Sky In and Around Swindon November 2017

Slide Presentation

The following presentation was given at our meeting on the 17th November, 2017 by Rob Slack

The constellation Hercules

Between the constellation Bootes and the bright star Vega in Lyra lies the constellation Hercules.The Red Giant star Alpha Herculis or Ras Algethi, its arabic name, is one of the largest stars known, with a diameter of around 500 times that of our Sun. In common with most giant stars it varies its size, changing in brightness as it does so from 3rd to 4th magnitude. Lying along one side of the "keystone" lies one of the wonders of the skies, the great globular cluster, M13. Just visible to the unaided eye on a dark clear night, it is easily seen through binoculars as a small ball of cotten wool about 1/3 the diameter of the full Moon. The brightness increases towards the centre where the concentration of stars is greatest. It is a most beautiful sight in a small telescope. It contains around 300,000 stars in a region of space 100 light years across, and is the brightest globular cluster that can be seen in the northern hemisphere.



The Globular Cluster M13 in Hercules.
Image by Yuugi Kitahara

The constellations 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 Lyrae
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"!

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 - The 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: 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
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.

Brocchi's Cluster - The Coathanger
The constellation Ursa Major
The stars of the Plough, shown linked by the thicker lines in the chart above, form one of the most recognised star patterns in the sky. Also called the Big Dipper, after the soup ladles used by farmer's wives in America to serve soup to the farm workers at lunchtime, it forms part of the Great Bear constellation - not quite so easy to make out! The stars Merak and Dubhe form the pointers which will lead you to the Pole Star, and hence find North. The stars Alcor and Mizar form a naked eye double which repays observation in a small telescope as Mizar is then shown to be an easily resolved double star. A fainter reddish star forms a triangle with Alcor and Mizar.

Ursa Major contains many interesting "deep sky" objects. The brightest, listed in Messier's Catalogue, are shown on the chart, but there are many fainter galaxies in the region too. In the upper right of the constellation are a pair of interacting galaxies M81 and M82 shown in the image below. M82 is undergoing a major burst of star formation and hence called a "starburst galaxy". They can be seen together using a low power eyepiece on a small telescope.


M81 and M82
Another, and very beautiful, galaxy is M101 which looks rather like a pinwheel firework, hence its other name the Pinwheel Galaxy. It was discovered in1781 and was a late entry to Messier's calalogue of nebulous objects. It is a type Sc spiral galaxy seen face on which is at a distance of about 24 million light years. Type Sc galaxies have a relativly small nucleus and open spiral arms. With an overall diameter of 170,000 light it is one of the largest spirals known (the Milky Way has a diameter of ~ 130,000 light years).

M101 - The Ursa Major Pinwheel Galaxy
Though just outside the constellation boundary, M51 lies close to Alkaid, the leftmost star of the Plough. Also called the Whirlpool Galaxy it is being deformed by the passage of the smaller galaxy on the left. This is now gravitationally captured by M51 and the two will eventually merge. M51 lies at a distance of about 37 million light years and was the first galaxy in which spiral arms were seen. It was discovered by Charles Messier in 1773 and the spiral structure was observed by Lord Rosse in 1845 using the 72" reflector at Birr Castle in Ireland - for many years the largest telescope in the world.

M51 - The Whirlpool Galaxy
Lying close to Merak is the planetary nebula M97 which is usually called the Owl Nebula due to its resemblance to an owl's face with two large eyes. It was first called this by Lord Rosse who drew it in 1848 - as shown in the image below right. Planetary nebulae ar the remnants of stars similar in size to our Sun. When all possible nuclear fusion processes are complete, the central core collpses down into a "white dwarf" star and the the outer parts of the star are blown off to form the surrounding nebula.


M97 - The Owl Planetary Nebula

Lord Rosse's 1848 drawing of the Owl Nebula
November - still a good month to observe Neptune and Uranus with a small telescope

Neptune came into opposition - when it is nearest the Earth - on the 2nd of September, so will still be well placed to spot this month. Its magnitude is +7.9 so Neptune, with a disk just 3.7 arc seconds across, is easily spotted in binoculars lying in the constellation Aquarius as shown on the charts. It rises to an elevation of ~27 degrees when due south. Given a telescope of 8 inches or greater aperture and a dark transparent night it should even be possible to spot its moon Triton.

Uranus reached opposition on October 19th and so is visible all night. It will be highest in the sky in the south around 1 am BST shining at magnitude 5.7 and with a disk 3.7 arc seconds across. It lies in Pisces, one degree and 18 arc minutes up to the right of Omicron Pisces as shown in the accompanying chart. Its turquoise green colour should be seen in a small telescope and it will be easily spotted in binoculars


Around the 18th of November (with no Moon in the sky): find M31 - The Andromeda Galaxy - and perhaps M33 in Triangulum

How to find M31
Image: Stellarium/IM

In the evening, the galaxy M31 in Andromeda is visible in the south The chart above 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 (18th November) - 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!

Compiled by Ian Morison - Jodrell Bank Centre for Astrophysics
November early mornings: November Meteors

A Leonid crossing the Sword of Orion
In the hours before dawn, November gives us a chance to observe meteors from two showers. The first that it is thought might produce some bright events is the Northern Taurids shower which has a broad peak of around 10 days but normally gives relatively few meteors per hour. The peak is around the 10th of November but then the Moon is close to third quartre so its light will intrude. The meteors arise from comet 2P/Encke. Its tail is especially rich in large particles and, this year, we may pass through a relatively rich band so it is possible that a number of fireballs might be observed!

The better known November shower is the Leonids which peak on the night of the 17th/18th of the month. Happily, the Moon is new so will not hinder our view. As one might expect, the shower's radiant lies within the sickle of Leo and meteors could be spotted from the 15th to the 20th of the month. The Leonids enter the atmosphere at ~71 km/sec and this makes them somewhat challenging to photograph but its worth trying as one might just capture a bright fireball. Up to 15 meteors an hour could be observed if near the zenith. The Leonids are famous becaus every 33 years a meteor storm might be observed when the parent comet, 55P/Temple-Tuttle passes close to the Sun. In 1999, 3,000 meteors were observed per hour but we are now halfway between these impressive events hence with a far lower expected rate.

November late night: Comet 2107 O1 (ASASSN)
Throughout November, with binoculars or a small telescope, it should be possible to spot Comet 2107 O1 (ASASSN) as it nears the Pole Star. It was discovered in July by the ' All Sky Automated Survey for Supernovae' and brightened rapidly. Its brightness is now falling but, at magnitude +8 or +9, should be visible with binoculars near the Pole Star this month.