The Night Sky June 2011
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
Io seen from the Galileo Spacescraft
NASA.
This is a lovely image of Io, Jupiter's innermost Moon, showing its potmarked surface strewn with volcanoes. An active volcano is seen in eruption. Io must thus have a molten interior and this is due to "tidal heating" caused by the gravitational forces acting on it by Jupiter.
Highlights of the Month
May: Observe Saturn in the evening sky and split a nearby double star, Porrima.
Cassini Image of Saturn
Image NASA
To see some of Damian Peache's Saturn Images: Damian Peache's website
Saturn can still be seen in the western sky after sunset. It lies in the constellation Virgo close to the star Porrima. As June begins, Saturn is 18 arc minutes south east of Gamma Virginis, Porrima, and they are closest on June 10th when just 15 arc minutes separates them. This apparent moving westwards towards Porrima is due to our changing viewpoint as the Earth orbits the Sun and is called retrograde motion. After the 10th, Saturn resumes its eastwards path across the sky. The rings are now ~7.5 degrees from the line of site and so Saturn appears brighter than for a couple of years, but it will not be until 2016 that they will be at their widest again. The outer A-ring and slightly brighter B (bright?) ring are separated by a dark band called the Cassini Division. A faint and elusive C (Crepe) ring between the B ring and Saturn's surface. A small telescope will easily show its largest moon, Titan, and show some bands around the surface. See further details below in the "Planets" section. Having viewed Saturn with a small telescope, move just a little to the right to see if you can split the double star Gamma Virginis. Porrima is made up of two identical stars, each of magnitude 3.5. Back in 1919, there were separated by 6 arc seconds, so could easily be split in a small telescope, but around 2005 (at periastron) the pair were so close that they could barely be split, but now they are opening out again and, this summer, should be separated by ~1.7 arc seconds. This means that with good seeing a small telescope should be able to split them again - so why not try?
June around midnight: Spot Brochi's Cluster
Brochi's Cluster - The Coathanger.
Image: Stellarium/IM
By midnight (BST) this month, the constellations Cygnus, Lyra and Aquila will have risen in the East. Their three brightest stars Deneb, Vega and Altair respectivly make up the "Summer Triangle". If you sweep with binoculars one third of the way from Altair towards Vega, you should spot Brocchi's Cluster usually called "The Coathanger" as this is exactly what it looks like - but seen upside down. Its not thought to be a real cluster but an "asterism" which is a chance grouping of stars.
21:20 BST on 15th June: A totally eclipsed Moon rising in the South-east.
Eclipsed Moon
Image: Ian Morison
If clear and given a low south-eastern horizon without too much haze, we will be able to see the rising of a totally eclipsed Moon. (This is asking quite a lot!) Totality ends at 23:03 BST but the Moon will have only reached an elevation of 4 degrees by this time. The Moon remains in the partial shadow of the Earth until 00:02 BST on the 16th and finally moves out of the Earth's shadow around 01:00 BST. Due to its low elevation it will appear particularly dark.
Around the 15th June: see the "Moon Illusion"
Moon Illusion Diagram
Around the middle of the month the Moon, near full, is seen low above the horizon as the Moon's declination is then close to its minimum. At the same time the Moon has an angular diameter of ~32 arc seconds as it is close to its closest distance from the Earth in its somewhat elliptical orbit. When we see a full Moon near the horizon it appears to be much larger than when seen higher in the sky - the so called "Moon Illusion". However, when highest in the sky its actual apparent size will be greater, not smaller as we will be ~1 Earth radii closer, one part in 60. I explained in my book "Introduction to Astronomy and Cosmology" what I think is the likely cause - though this was hotly disputed by a reviewer! We perceive the dome of the sky not as a hemisphere with all parts equidistant but flattened with the sky above appearing much closer to us that that near the horizon. (This will be true of clouds, of course.) If we see something that we believe to be far away, we tend to "see" it larger than if we think that it is close. We think that a Moon seen near the horizon will be further away and so our mind makes it appear larger.
Dawn June 28th: A thin Crescent Moon and three planets in the pre-dawn sky
Planets and the Crescent Moon
Image: Stellarium/IM
Looking East-Southeast around 40 minutes before sunrise on the morning of June 28th and given a good low horizon in that direction you will see, if clear, a nice skyscape with a very thin crescent Moon up and to the right of the planet Venus, shining brightly at magnitude -3.8 but low above the horizon. About 1/3rd of the way from the Moon towards Venus lies 1.4 magnitude Mars, itself seen above Aldabaren - an "interloper" in the Hyades Cluster. Jupiter lies up and to the right of the Moon. The Pleiades Cluster may also be seen just above and to the left of the Moon. Note: The sky brightness has been reduced in this image to enable the planets to be seen - binoculars may well be need to spot them! But do NOT use binoculars once the Sun has risen!
June 8th/9th: The Alpine Valley
Alpine Valley region
An interesting valley on the Moon: The Alpine Valley
These are two good nights to observe an interesting feature on the Moon if you have a small telescope. Close to the limb (on the 8th) is the Appenine mountain chain that marks the edge of Mare Imbrium. Towards the upper end you should see the cleft across them called the Alpine valley. It is about 7 miles wide and 79 miles long. As shown in the image a thin rill runs along its length which is quite a challenge to observe. Next evening the dark crater Plato and the young crater Copernicus will come into view. This is a very interesting region of the Moon!
The Alpine valley and the crater Plato
A Messier Object imaged with the Faulkes Telescope: the Trapezium in M27 - the Dumbell Nebula.
The Dumbell Nebula
Image:Nik Szymanik
Faulkes Telescope North.
The Dumbell Nebula, imaged by Nik Szymanek.
This image was taken using the Faulkes Telescope North by Nik Szymanek - one of the UK's leading astro-photograpers. M27 is a planetary nebula, the result of a "nova" expolsion at the end of the life of a star like our Sun. The core at the centre of the star collapes under gravity until it is about the size of the Earth when "electron degeneracy pressure", resulting from the fact that electrons do not like being squashed too close together, prevents further collapse. This is called a "white dwarf". As the dying ember of a nuclear fusion reactor, they are exceedingly hot, but will gradually cool over time. The outer parts of the star are expelled at high speed into space resuting in the (in this case) spherical nebula surrounding the white dwarf. The field of the view of the CCD array on the Faulkes Telesocpe is a little too small to encompass the whole nebula. Once, with a 16 inch telescope under perfect conditions, I visually observed M27 and its central part appeared a vivid iridescent green - the only time I have ever seen colour in a deep sky object!
Learn more about the Faulkes Telescopes and how schools can use them: Faulkes Telescope"
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 |
|---|---|---|---|
| June 1st | June 9th | June 15th | June 23rd |
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.
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. JPL / Nasa
Jupiter
A Cassini image of Jupiter . Nasa
Jupiter is now a pre-dawn object but, as the ecliptic is inclined at a relatively low angle to the dawn horizon, as it moves further in angle from the Sun its elevation will remain quite low. Its magnitude will will slightly increase from -2.1to -2.2 during the month and it will have an angular size of 35 increasing to 36.5 arc seconds. It is not really a good month to observe the details on its surface due to its low elevation.
See Highlight above.Saturn
The planet Saturn. Cassini - Nasa
Saturn. Saturn is now a late evening object visible low in the Southwest after sunset. It starts June with a magnitude of +0.8 and, as the month progresses, its brightness decreases a little to +0.9. Compared to early last year, its apparent brightness has now increased as the rings have opened out again - now tilted at +7.5 degrees from edge on. In fact, due to the changing aspect from Earth, the tilt angle has been reducing this year to this month's minima and we will have to wait until late in the year when it becomes a morning object to see them at a significantly wider angle. The plus sign indicates that we are seeing Saturn's north pole. The rings span an angular size of ~40 arc seconds - over double the 18 arc seconds of the planet's disk. Given a small telescope it should be possible to see Cassini's division - a dark band that separates the A and B rings. It will also show Saturn's brightest moon, Titan, (at magnitude +8) and, given good conditions, other moons as well.
See Highlight above.
Mercury
Messenger image of Mercury Nasa
Mercury passes behind the Sun on June 12th so will not be visible until the end of the month when, on the 23rd, it will have a magnitude of -1.0 just visible in the late evening twilight above the West-North-western horizon. Perhaps see where the Sun sets on the horizon at about 9 pm and look in the same direction with binoculars about 45 minutes later. By month's end, when 19 degrees in angle from the Sun and some 10 degrees above the horizon at sunset, it will be somewhat fainter at -0.9 magnitudes and show a ~6 arc second disk which is 76% illuminated.
Mars
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa
Mars is now visible in the pre-dawn sky but again, as the ecliptic is at a shallow angle to the horizon, it will have a very low elevation. To spot it, a good, low, eastern horizon and, quite probably, a pair of binoculars will be needed. This month, its magnitude increases a fraction from +1.3 to +1.4 and its angular size will be touch over 4 arc seconds. By month's end it will be 32 degrees west of the Sun and have an elevation of ~17 degrees at sunrise lying in the constellation Taurus between the Hyades and Pleiades clusters.
See Highlight above.
Venus
Venus showing some cloud structure
Venus remains a pre-dawn object shining at a magnitude of -3.8 throughout the month when it can be seen in the pre-dawn sky rising about 40 minutes before the Sun. As it moves towards the far side of the Sun, its angular size is reducing - now about 10 arc seconds - but at the same time we see more of its disk illuminated (~95%) so its apparent magnitude remains unchanged. On June 8th it passes 6 degrees below the Pleiades cluster and, on June 18th, is just 5 degrees above Aldebaran - the eye of the bull.
See Highlight above.
Radar image showing surface features
Find more planetary images and details about the Solar System: The Solar System
The Stars
The late evening June Sky
The June Sky in the south - late evening.
This map shows the constellations seen towards the south at about 11pm BST in mid June. 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 southern 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
