The Night Sky August 2009
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.
Image of the Month
The Apollo 11 and 14 landing sites.
Image: LRO,NASA
NASA's Lunar Reconnaisance Orbiter, or LRO, reached Lunar orbit on June 23rd. The orbit will will finally drop to about 30km above the surface giving images with two to three times higher resolution than those shown above. It has passed over some of the Apollo sites when the Sun was low above the horizon and has observed the descent stage of the Lunar Excursion Modules (LEMs) casting their shadow across the lunar surface. In the case of the Apollo 14 image the tracks across the surface to where the Apollo Lunar Science Package (ALSEP) was located are clearly seen as is the ALSEP itself. It is very nice that these images have been released to coincide with the the 40th Anniversary of the Apollo 11 landing. Perhaps the sceptics will finally agree that Apollo really did go to the Moon!
Highlights of the Month
August 11th to 14th: View the Perseid Meteor Shower
A Perseid Meteor
Image: S. Kohle and B. Koch, Astronomy Institute, Bonn University.
If it is clear on the 11th and 12th of August, one will have a chance of seeing the meteors in the Perseid Meteor Shower - the year's most dependable meteor shower. It is not, perhaps,the best year to observe the Perseids as a waning gibbous Moon will be rising in the north-east and its glare will obscure the fainter meteors. Look up towards the North-East from 11 pm onwards on the nights of August 11th, 12th and 13th and 14th. After midnight, as Perseus rises higher into the sky, the numbers seen may well rise too! Most meteors are seen when looking about 50 degrees away from the "radiant" (the point from which the meteors appear to radiate from) which lies between Perseus and Cassiopea. (See the star chart below) The Perseid meteors are particles, usually smaller than a grain of sand, released as the comet Swift-Tuttle passes the Sun. The shower in quite long lived, so it is worth looking out any night from the 10th to the 15th of August. This last day could well be the best as the Moon will be rising later and be less bright. Good hunting!
Looking East after midnight on 11th August
Image: Stellarium/Ian Morison
August 3rd: See Jupiter occult a star!
Jupiter's Moons and 45 Capricorni
Image: Stellarium/IM
If you observe Jupiter in the first week of August you may be surprised to observe 5, not 4, Galilean moons! There is an interloper, the +5.9 magnitide star 45 Capricorni, which is only just fainter than Callisto. If you have a telescope of 6 inches or more, you may well see that whilst the satellites of Jupiter appear as tiny discs, the star will look pointlike. As Jupiter passes westwards across the sky it will occult (pass in front of) the star at 11:52 BST on August 3rd. 45 Capricorni will emerge almost two hours later at 02:00 BST on the morning of the 4th August.
Early August: Saturns rings dissapear!
Saturn just after sunset on the 9th August
Image Stellarium
During the first two weeks of August, Saturn may still be seen low above the western horizon just after sunset. You may well not observe any rings as, on the 9th of August, they are edge on to the Sun and will thus not be illuminated! Thereafter the rings are tilted so that they will be illuminated on their other side from us and not be directly visible. One will observe a thin dark line bisecting Saturn which is partly a silhouette of the rings and partly their shadow on Saturn's surface. Sadly Saturn, by then, will be increasingly lost in the glare from the Sun.
August 6th early morning: A penumbral eclipse of the Moon
The Moon after midnight on August 6th
Image Stellarium/IM
Full Moon occurs just after midnight on the 6th of August. This is, of course, when eclipses of the Moon can occur and this month there is a penumbral eclipse when the lower third of the Moon will lie in the partial shadow of the Earth and so will appear somewhat dimmer and have a flatter, dull grey, tone.
Observe 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
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 20nd | August 27th | August 6th | August 13th |
Some Lunar Images by Ian Morison, Jodrell Bank Observatory: Lunar Images
A 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.
Please follow the link to go to the 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.
Plato and the Alpine Valley.
The Lunar World Record 2009: Lunar World Record
The Planets
A montage of the Solar System. JPL / Nasa
Jupiter
A Cassini image of Jupiter . Nasa
Jupiter, now lying in Capricornus, becomes more easily visible this month rising soon after twilight. During August its magnitude remains pretty constant at -2.8 as, on August 14th, Jupiter is at opposition - that is opposite the Sun and so approximately due south at midnight - and thus its distance from us does not change that much during the month. It has an angular size of 48 arc seconds so a small telescope will show much detail on the surface if seeing conditions are good. Sadly at the present time Jupiter is close to the lowest part of the ecliptic and never reaches more than ~25 degrees above the horizon even when it will be seen due south, so highest in the sky. It will lie to right of the almost full Moon on the 6th of August. One problem with observing Jupiter with a telescope when it is so low in the sky is refraction in the atmosphere. This shifts the different colours of light in Jupiters image by differing amounts, so giving a blurred image. Using a green filter will help considerably in giving a cleaner image and I have even used a very narrow band OIII filter to observe Jupiter in monochromatic light giving excellent results. See also highlight above.
Saturn
The planet Saturn. Cassini - Nasa
Saturn is just be seen seen as twilight deepens lying in Leo - but somewhat below the main body of the Lion. You will need a very low western horizon to spot it though! Its magnitude is +1.1 - not as bright as usual, with Saturn significantly less bright this year than it sometimes is: the rings are very close to edge on and thus there is less apparent reflecting area. At the beginning of August they are at an angle of just 1.9 degrees from the line of sight! This narrows to during the month as they will be edge on to the Earth on September 4th. However they are edgewise on August 10th so it might be posible to see that they have turned from bright to dark! Those with a computer controlled telescope might be able to pick up Saturn whilst it is higher in the sky before the the sky darkens significantly. It will not be until 2016 that they will be at their widest again. A small telescope will easily show its largest moon, Titan, and show some bands around the surface. See highlight above
Mercury
Messinger image of Mercury Nasa
Mercury: may be seen, probably with the help of binoculars, low in the west but in bright twilight. It dims from magnitude -0.4 to magnitude +0.4 during the month. It will lie just 0.6 degrees above the star Regulus in Leo on the 2nd of August and passes 3 degrees from Saturn on the 26th, but I suspect that both planets will, by then, have been lost into the glare of the Sun.
Mars
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa
Mars is becoming more prominent in the pre-dawn sky this month as it rises just after midnight and will be seen in the east before dawn. It has a magnitude of +1. Its angular size will increase from 5.3 to 5.8 arc seconds during the month so, under ideal seeing conditions, a telescope might begin to show some of the more prominent features such as Syrtis Major. We will have to wait a month or so until it will be seen more easily as the nights get longer and it rises earlier in the night! The Earth will, of course, be overtaking Mars "on the inside track" so we will come closer to it and its angular size will increase so allowing more features on the surface to be seen.
Venus
Venus showing some cloud structure
Venus Venus is moving increasingly further away from the Sun and by mid month will be 27 degrees above the eastern horizon by sunrise. A small telescope will show a waxing gibbous disc dropping from 14.8 arc seconds in diameter to 12.6 arcseconds as it moves towards the far side of the Sun. It magnitude drops from -4 to -3.9 during the month. An interesting fact about its brightness is that it stays pretty constant at about -4 for most of the time that it is visible even though the apparent phase changes greatly. When the phase is thin, Venus is nearer to us and so the effective reflecting area of Venus as seen from Earth remains pretty constant.
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
The August Sky in the south - mid evening.
Having virtually never seen the night sky in July, let's just hope that August will be better! Now that the evenings are drawing it 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
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
The constellation 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.
The Globular Cluster M13 in Hercules. Image by Yuugi Kitahara
The constellation 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.
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.
M104 - The Sombrero Galaxy
The constellations Lyra and Cygnus
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!
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
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
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.
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
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
