The Night Sky July 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 most distant explosion ever seen!
Image: Gemini Observatory/NSF/AURA.
In April an explosion was observed by the NASA Swift Observatory from across most of the visible Universe and then the afterglow was imaged by the 8-m Gemini North Telescope in Hawaii. The source of the explosion, called a "Gamma Ray Burst" lies at a redshift of 8.2 which means that it occured just 630 million years after the origin of the Universe in the "Big Bang". It seems likely that it was the final event in the life of one of the first massive stars to form in the Universe and announced the birth of a "Black Hole". Had someone been looking in the right direction at the time from a dark location, it would have been visible to the human eye and he or she would have seen back in time about 13 billion years!
Highlights of the Month
July 10th: A nice line-up of Jupiter's Galliean satellites.
Jupiter's Moons
Image: Stellarium
On the morning of July 10th, the 4 Gallilean satellites, Io, Europa, Ganymede and Callisto will all lie to its lower right Use as high a magnification as you can to just encompass Jupiter and its satellites as this will make the sky background darker and so make the satellites show up more easily.
July 13th: Venus with the Hyades Cluster
July 13th : Early Morning.
Image Stellarium/IM
On the morning of the 13th July, Venus (at magnitude -4.1) passes just 9 arc minutes degrees from the star Epsilon Tauri (at magnitude 3.5) in the Hyades Cluster. One for early risers!
July: Still a very good time to spot Noctilucent Clouds!
June: the chance to spot Noctilucent Clouds
Image: Wikipedia Commons
Noctilucent clouds, also known as polar mesospheric clouds, are most commonly seen in the deep twilight towards the north from our latitude. They are the highest clouds in the atmosphere at heights of around 80 km or 50 miles. Normally too faint to be seen, they are visible when illuminated by sunlight from below the northern horizon whilst the lower parts of the atmosphere are in shadow. They are not fully understood and are increaing in frequencey, brightness and extent; some think that this might be due to climate change! So on a clear dark night as light is draining from the north western sky long after sunset just take a look towards the north and you might just spot them!
July 10th: Spot Neptune very close in the sky to Jupiter.
June 4th: Pre-dawn Sky
Image Stellarium/IM
During July, Jupiter and Neptune continue to be close together in the sky and are at their closest on July 10th when Neptune, at magnitude 7.8, lies just 34 arc minutes above Jupiter, at magnitude -2.8. The 5.1 magnitude star Mu Capricornus lies between the two down making a very thin triangle with Neptune and Jupiter. Given a transparent sky it should be easily spotted in 8 x 40 binoculars. Neptune remains very close to Mu Capricornus throughout the month but with Jupiter moving relatively further to the lower right, but still less than 2 degrees away by month's end. Could well be worth getting up for!
July 18th: The Moon occults the Pleiades Cluster.
July 18th: Pre-dawn Sky
Image Stellarium
On the morning of the 18th of July, the Moon will be seen to occult some of the stars of the Pleiades Cluster
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 | first quarter | full moon | last quarter |
|---|---|---|---|
| July 22nd | July 28th | July 7th | July 15th |
Some Lunar Images by Ian Morison, Jodrell Bank Observatory: Lunar Images
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 as its elevation in the early morning sky is getting higher - about 24 degrees above the horizon at the start of July. It rises at about 23:00 UT at the beginning of July and 21:00 UT by its end. During July its magnitude slowly increases from -2.7 to -2.8. 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, later this year. It will lie to the lower left of the the Moon on the 13th of July in the sky after midnight. 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 +0.7 - 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 July they are at an angle of just 3.2 degrees from the line of sight! This narrows to just 1.9 degrees during the month but, by then, Saturn will be swallowed up by the glare of the Sun. The rings will be seen (or rather - not seen) edge-on later this year and 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.
Mercury
Messinger image of Mercury Nasa
Mercury: reached what is called "Western Elongation" on the 13th June when it lay furthest in angle from the Sun and best seen before sunrise. However it is now closing rapidly on the sun's position and may only be glimpsed low in the east-northeast just before dawn duing the first few days of July. Its elevation will be very low, and binoculars will almost certainly be needed to spot it (NB before the Sun rises!) at magnitude -1.3 given a very low north-eastern horizon.
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 and is at an elevation of 25 degrees due east as the Sun rises on the 1st of July. It has a magnitude of +1.1. Its angular size has increased to 5 arc seconds 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!
Venus
Venus showing some cloud structure
Venus is now easily visible in the pre-dawn sky having risen at 01:44 on July 1st. It will lie 20 degrees degrees above the horizon as the Sun rises that morning. By month's end it will be very obvious and seen at an elevation of 28 degrees due east as the Sun rises. It is at magnitude -4.1 at mid month, and lies just to the lower left of Mars. 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 July Sky
The July Sky in the south - mid evening.
This map shows the constellations seen towards the south at about 10pm BST in mid July. High overhead 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 Aquilla. 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
