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The Night Sky August 2015

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.



Cambridge University Press has recently published two books by the author. An Amateurs Guide to Observing and Imaging the Heavens is a handbook aimed to bridge the gap between the beginner's books on amateur astronomy and the books which cover a single topic in great detail.   Stephen James O'Meara and Damian Peach have both given it excellent reviews. 'A Journey through the Universe' covering our current understanding of the Universe (up to June last year) was published on the 25th of September.   Martin Rees has written a very nice review of it.


Image of the Month

Charon imaged by New Horizons

Charon

Charon

Image: NASA,John Hopkins Univ./APL,Southwest Research Institute.

Of all the images so far sent back by New Horizons, this is the one I like best.   Charon was discovered by Jim Christy in 1978 and this allowed the mass of Pluto to be calculated - it was far smaller and less massive that had been thought when it was discovered and, to be honest, if Pluto were discovered now it would never be classified as a planet.   I was a little sad though when it was demoted and would have liked it to have been allowed to stay as an 'honorary planet'.   Charon is 1,200 km across - half the diameter of Pluto and about 1/10th the size of Earth.   Its terrain is surprisingly youthful and very varied including a 1,000 km swath of cliffs and troughs seen below the centre of the image and, along the upper right edge, a 7 to 9 km deep canyon.   The enigmatic dark polar region has been dubbed 'Mordor'!

Highlights of the Month


August - 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 high in the 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



August - A good month to observe Neptune with a small telescope.

Neptune
Neptune in Aquarius
Image: Stellarium/IM

Neptune comes into opposition - when it is nearest the Earth - on the 31st of August, so will be seen well both this month and next.   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 chart.   It rises to an elevation of ~27 degrees when due south.   Given a telescope of 8 inches or greater aperture and a dark tranparent night it should even be possible to spot its moon Triton. (This is my objective around the end of the month!)   It lies very close to the 7th magnitude star HIP 111910 and, on the 5th of September, will lie directly above it.


August 7th after sunset: Jupiter and Mercury close to Regulus in Leo.

Jupiter
Jupiter, Mercury close to Regulus in Leo.
Image: Ian Morison

One of the last chances to see Jupiter this apparition in on the 7th.   Given clear skies and a low western horizon it should be possible to spot Jupiter and Mercury within a one degree diameter circle with the star Regulus in Leo.

Both planets will be then nearly fully lit, but Jupiter's 31 arc second disk will appear significantly less bright than Mercury's disk, some six times smaller.

August 8th - 45 minutes before sunrise: Mars below Castor and Pollux in Gemini

Mars
Mars below Castor and Pollux
Image: Stellarium/IM

Before sunrise on the 8th of the month there is a chance of spotting Mars, with a magnitude of +1.7 and angular diameter of 3.7 arc seconds, at the start of its new apparition lying, in Gemini below Castor and Pollux.  

The good news is that when Mars it at its closest in May next year, its angular diameter will reach 18.6 arc seconds in comparison to the meagre 14 arc seconds peak during the last two apparitions.   Sadly it will be then be at a rather low elevation.

The mornings of August 12th and 13th and 14th: midnight to dawn - look out for the Perseid meteor shower.

Perseids
A Perseid meteor

If clear, these mornings should give us a chance of observing the Perseid meteor shower - produced by debris from the comet Swift-Tuttle.   The peak of the shower is after sunrise on the morning of the 13th so the early morning of the 13th August will give us the best chance, if clear, of viewing the shower, but the peak is quite broad and so its well worth observing on the nights before and after.   Most meteors are seen looking about 50 degrees from the "radiant" which lies between Perseus and Cassiopeia.   The great thing about this year is that, with New Moon on the 14th, there will be no moonlight to hinder our view in the days around the peak.   Under cloudless skies and from a dark location observers might expect to see 50 to 70 meteros an hour near the peak (the last hours of darkness on the morning of the 13th).

Perseids
Looking East at ~1am on the morning of the 13th August
Image: Stellarium/IM

August 22nd - one hour after sunset: Saturn close to a first quarter Moon - and a lunar occultation of Theta Librae.

Saturn
Saturn close to a first quarter Moon..
Image: Stellarium/IM

Looking west after sunset, Saturn, in Libra, will be seen close to a first quarter Moon.   A good horizon in the South South-west will be needed.   Whilst producing the diagram using the Stellarium program, I spotted the, 4th magnitude, star Theta Librae very close to the Moon's dark limb.   It should be seen to dissapear behind the limb around 21:41 BST.

Occultation
Theta Librae occulted by the Moon.

August 7th and 23rd: The Straight Wall

Moon
Location of the Straight Wall: IM.

The Straight Wall
The Straight Wall is best observed either 1 or 2 days after First Quarter (23rd August: evening best) or a day or so before Third Quarter (evening of the 7th August best).   To honest, it is not really a wall but a gentle scarp - as Sir Patrick has said "Neither is it a wall nor is it straight!".

The Straight Wall
The Straight Wall at Sunrise and Sunset.

A Messier Object imaged with the Faulkes Telescope: galaxy NGC 1365.

Galaxy NGC 1365
NGC1365
Image:Nik Szymanik
Faulkes Telescope.

Galaxy NGC 1365, imaged by Nik Szymanek.
This image was taken using the Faulkes Telescope by Nik Szymanek - one of the UK's leading astro-photograpers.   NGC1365 is also known as the Great Barred Spiral Galaxy and lies at a distance of 56 million light years.   It is one of the most perfect barred spirals with a straight bar and two very prominent spiral arms.   Closer to the centre there is also a second spiral structure.   The galaxy is an excellent "laboratory" for astronomers to study how galaxies form and evolve.

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 last quarter
August 14th August 22nd August 29th August 7th

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 9550 pixels. This 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 Planets

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

Jupiter

Jupiter
A Cassini image of Jupiter . Nasa

Jupiter passes behind the Sun on August 26th so can only be observed during twilight at the very beginning of the month low in the west after sunset.   Venus passed 6 degrees below Jupiter on July 31st so will be close for the first few days of the month but becoming progressivly more difficult to observe.   It was good to observe the two close together, still reasonably high in the sky during twilight, during the first part of July.



See highlight above.


Saturn

Saturn
The planet Saturn. Cassini - Nasa

Saturn is the only bright planet visible outside twilight this month. It lies in Libra near the wide double star Alpha Librae falling in brightness a little from +0.4 to +0.5 magnitudes during the month.   It ceases its retrograde motion westwards in the sky on August 2nd and so begins to move eastwards back towards Scorpius.   One hour after sunset it will lie just 20 degrees above the horizon so the atmosphere will limit the view of its 17 arc second disk but the ring system, now 24 degrees open, should still show nicely along with Titan, its largest satellite.   Saturn will be 90 degrees east of the Sun (eastern quadrature) on August 21st so the globe's shadow on the rings is at its maximum extent giving a three-dimensional feel to our view of this, most beautiful, planet.


See highlight above.


Mercury

Mercury.
Messenger image of Mercury Nasa

Mercury .   This month Mercury returns to the twilight sky before sunset increasing in brightness from +1.2 to +0.1 during the month as it rises a little higher in the western sky.



See highlight above.


Mars

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

Mars. As August begins, Mars, shining at magnitude +1.7, rises about 70 minutes before the Sun.   This increases to 2 hours by month's end with its brightness virtually unchanged at +1.8 magnitudes.   On August 8th, at an elevation of just 5 degrees, it will lie below Castor and Pollux in Gemini around 45 minutes before sunrise whilst on the mornings of the 20th and 21st it will lie close the M44, the Beehive Cluster in Cancer.


Venus

Venus
Venus showing some cloud structure

Venus, rises at sunrise on the 18th of August, but 55 minutes before the Sun a week later and about one hour 30 minutes by month's end.   As it does so, its brightness brightens from -4.1 to -4.5 magnitudes and its angular size reduces slightly from 58 to 52 arc seconds whilst the percentage illuminated area (phase) of the planet increases from 1 to 9%.   So close to the Sun, it is not safe to observe after sunrise.



Radar Image of Venus
Radar image showing surface features



Find more planetary images and details about the Solar System: The Solar System



The Stars

The mid evening August Sky

July Sky
The August Sky in the south - mid evening.

Now that the evenings are drawing in, the night sky gets darker earlier so encouraging one to go out to observe.

This map shows the constellations seen towards the south at about 10pm BST in mid August. High over head towards the north (not shown on the chart) lies Ursa Major. As one moves southwards one first crosses the constellation Hercules with its magnificent globular cluster, M13, and then across the large but not prominent constellation Ophiucus until, low above the souther horizon lie Sagittarius and Scorpio. To the right of Hercules lie the arc of stars making up Corona Borealis and then Bootes with its bright star Arcturus. Rising in the east is the beautiful region of the Milky Way containing both Cygnus and Lyra. Below is the constellation of Aquilla, the Eagle. The three bright stars Deneb (in Cygnus), Vega (in Lyra) and Altair (in Aquila) make up the "Summer Triangle".

The constellation Ursa Major

Ursa Major
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
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
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
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.

Owl Nebula Owl Nebula
M97 - The Owl Planetary Nebula Lord Rosse's 1848 drawing of the Owl Nebula

The constellation Hercules

Hercules
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.

Globular Cluster M13
The Globular Cluster M13 in Hercules. Image by Yuugi Kitahara

The constellation Virgo

Virgo
Virgo

Virgo, in the south-east after sunset this month, is not one of the most prominent constellations, containing only one bright star, Spica, but is one of the largest and is very rewarding for those with "rich field" telescopes capable of seeing the many galaxies that lie within its boundaries. Spica is, in fact, an exceedingly close double star with the two B type stars orbiting each other every 4 days. Their total luminosity is 2000 times that of our Sun. In the upper right hand quadrant of Virgo lies the centre of the Virgo Cluster of galaxies. There are 13 galaxies in the Messier catalogue in this region, all of which can be seen with a small telescope. The brightest is the giant elliptical galaxy, M87, with a jet extending from its centre where there is almost certainly a massive black hole into which dust and gas are falling. This releases great amounts of energy which powers particles to reach speeds close to the speed of light forming the jet we see. M87 is also called VIRGO A as it is a very strong radio source.

M87 MERLIN images
The Giant Elliptical Galaxy M87 HST image showing the jet

Below Porrima and to the right of Spica lies M104, an 8th magnitude spiral galaxy about 30 million light years away from us. Its spiral arms are edge on to us so in a small telescope it appears as an elliptical galaxy. It is also known as the Sombrero Galaxy as it looks like a wide brimmed hat in long exposure photographs.

The Sombrero Galaxy
M104 - The Sombrero Galaxy

The constellations Lyra and Cygnus

Cygnus and Lyra
Lyra and Cygnus

This month the constellations Lyra and Cygnus are rising in the East 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.

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!

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