The Night Sky May 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
Yuri Gagarin's Earth
ISS Expedition 7, EOL, NASA.
This stunning image of the Earth was taken from the International Space Station in 2003. It is to remind us of the view that Yuri Gagarin would have seen on his space flight around the Earth on April 12th, 1961. He said that "The sky is very dark, the Earth is Blue." His Vostok 1 spacecraft orbited the Earth once at a height of 200 miles and his view would have been much like this as the ISS orbits at a height of 192 miles.
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 is now well up in the southern sky during the evening lying in the constellation Virgo close to the star Porrima. The rings are now ~ 8 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 or Porrima. 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 spring, 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?
Dawn May 1st: A thin Crescent Moon and four planets in the pre-dawn sky
Planets and the Crescent Moon
Image:Stellarium/IM
May 6th before dawn: The Eta Aquarid Meteor Shower
The Eta Aquarid Meteor Shower
Image:Stellarium/IM
Dawn on May 29th to 31st: Four planets and a Crescent Moon in the pre-dawn sky
Dawn Planets
Image:Stellarium/IM
On the last three mornings of the month, given a clear low eastern horizon, there will be four planets and a thin crescent Moon visible just above the horizon During the month their relative positions have shifted, so now Jupiter is highest in the sky towards the south. Lying in line down to the horizon will be seen, first Mars, then Venus and finally, just above the horizon Mercury. During the three days the Crescent Moon will pass above them becoming a thinner crescent as it does so. Note: The sky brightness had been reduced to show the planets - you will need binoculars, so cease looking when the Sun has risen!
May 14th/15th: Schroter's valley on the Moon
Schroter's valley
An interesting valley on the Moon: Schroter's 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 14th) is the bright crater Aristachus, some 41km in diameter. It is a young crater, some 450 million year old and shows some rays projecting from it. It lies close to the 36km diameter crater Herodotus which is close to the starting point for the very interesting "Schroter's Valley". This extends north, then west, for ~97 km and has a width of 6 to 9km. It has a depth of ~1 km. The upper image shows how it appears as seen from Earth in an inverting telescope, whilst the lower is an image looking south taken by the Apollo 15 astronauts.
Schroter's Valley and Aristarchus
A Messier Object imaged with the Faulkes Telescope: the Trapezium in M42 - the Orion Nebula.
The Trapezium in M42
Image:Nik Szymanik
Faulkes Telescope North.
The Trapezium stars in M42, imaged by Nik Szymanek.
This image was taken using the Faulkes Telescope North by Nik Szymanek - one of the UK's leading astro-photograpers. It shows the stars - called "The Trapezium" - at the heart of the Great Nebula in Orion, or M42. In a small telescope only 4 stars can normally be seen but, under very good seeing, when the atmosphere is very stable, a fifth may become visible. You can compare the incredible detail in this image with that taken by the author using a small 4" telescope at sea level coupled to a DSLR. The Orion Nebula is the nearest star formation region to the Sun, lying at a distance of ~1,300 light years. The ultraviolet light from the very hot stars that make up the Trapezium is exciting the hydrogen gas to give off the pink-red Hydrogen Alpha emission line.
Learn more about the Faulkes Telescopes and how schools can use them: Faulkes Telescope"
Orion nebula with the trapezium at its heart.
Image: Ian Morison
Takahashi FS102/Nikon D7000
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 |
|---|---|---|---|
| May 3rd | May 11th | May 17th | May 24th |
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 passed behind the Sun on April 6th and just became visible towards the end of the month when it rose shortly before the Sun. So, as May progresses, it will gradually rise earlier than the Sun and become easier to see above the eastern horizon. Its magnitude will remain at -2.1 throughout the month and it will have an angular size of 33 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 an evening object. It reached opposition to the Sun on the night of April 3rd/4th so, in May, will be seen due south, and hence highest in the sky, in the evening making it ideal to observe. It starts May with a magnitude of +0.5 and, as the month progresses, its brightness decreases a little to +0.7. Compared to last year, its apparent brightness has now increased as the rings have opened out again - now tilted at +8 degrees from edge on. The plus sign indicates that we are seeing Saturn's north pole. The rings span an angular size of 43 arc seconds - over double the 19 arc seconds of the planet's disk. Given a small telescope it should now 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 is visible low above the eastern horizon this month and binoculars will be needed to spot it. It reaches greatest western elongation (when it it at its greatest angular separation from the Sun) on the 7th May but, due to the fact that the ecliptic makes a very shallow angle to the dawn horizon at this time of year makes it very hard to spot.
See Highlight above.
Mars
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa
Mars has now passed behind the Sun and emerges into the pre-dawn sky towards the middle of April but, 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 a pair of binoculars will be needed. This month, its magnitude increases a fraction to +1.3 during the month and its angular size is ~4 arc seconds. Binoculars will be needed to spot it until the end of the month.
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 an hour before the Sun. But, though its angular separation from the Sun is still large, it is not that high above the eastern horizon. As it moves towards the far side of the Sun, its angular size is reducing - from 11.6 arc seconds down to 10.6 arc seconds during the month - but at the same time we see more of its disk illuminated (from 88% up to 93%) so its apparent magnitude remains unchanged.
See Highlight above.
Radar image showing surface features
Find more planetary images and details about the Solar System: The Solar System
The Stars
The evening May Sky
The May Sky in the south - after sunset.
This map shows the constellations seen in the south after sunset.
The constellation Gemini is now setting towards the south-west and Leo holds pride (sic) of place in the south with its bright star Regulus. Between Gemini and Leo lies Cancer - which is well worth observing with binoculars to see the Beehive Cluster at its heart. Below Gemini is the tiny constellation Canis Minor whose only bright star is Procyon. Rising in the south-east is the constellation Virgo whose brightest star is Spica. Though Virgo has few bright stars it is in the direction of of a great cluster of galaxies - the Virgo Cluster - which lies at the centre of the supercluster of which our local group of galaxies is an outlying member. High overhead in the north is the constellation Ursa Major which also contains many interesting objects.
The constellation Gemini
Gemini
Gemini - The Twins - lies up and to the left of Orion and is in the south-west during early evenings this month. It contains two bright stars Castor and Pollux of 1.9 and 1.1 magnitudes respectivly. Castor is a close double having a separation of ~ 3.6 arc seconds making it a fine test of the quality of a small telescope - providing the atmospheric seeing is good! In fact the Castor system has 6 stars - each of the two seen in the telescope is a double star, and there is a third, 9th magnitude, companion star 73 arcseconds away which is alos a double star! Pollux is a red giant star of spectral class K0. The planet Pluto was discovered close to delta Geminorum by Clyde Tombaugh in 1930. The variable star shown to the lower right of delta Geminorum is a Cepheid variable, changing its brightness from 3.6 to 4.2 magnitudes with a period of 10.15 days
M35 and NGC 2158
This wonderful image was taken by Fritz Benedict and David Chappell using a 30" telescope at McDonal Observatory. Randy Whited combined the three colour CCD images to make the picture
M35 is an open star cluster comprising several hundred stars around a hundred of which are brighter than magnitude 13 and so will be seen under dark skies with a relativly small telescope. It is easily spotted with binoculars close to the "foot" of the upper right twin. A small telescope at low power using a wide field eyepiece will show it at its best. Those using larger telescopes - say 8 to 10 inches - will spot a smaller compact cluster NGC 2158 close by. NGC 2158 is four times more distant that M35 and ten times older, so the hotter blue stars will have reached the end of their lives leaving only the longer-lived yellow stars like our Sun to dominate its light.
The Eskimo Nebula, NGC2392, Hubble Space Telescope
To the lower right of the constellation lies the Planetary Nebula NGC2392. As the Hubble Space Telescope image shows, it resembles a head surrounded by the fur collar of a parka hood - hence its other name The Eskimo Nebula. The white dwarf remnant is seen at the centre of the "head". The Nebula was discovered by William Herschel in 1787. It lies about 5000 light years away from us.
The constellation Leo
Leo
The constellation Leo is now in the south-eastern sky in the evening. One of the few constellations that genuinely resembles its name, it looks likes one of the Lions in Trafalger Square, with its manem and head forming an arc (called the Sickle) to the upper right, with Regulus in the position of its right knee. Regulus is a blue-white star, five times bigger than the sun at a distance of 90 light years. It shines at magnitude 1.4. Algieba, which forms the base of the neck, is the second brightest star in Leo at magnitude 1.9. With a telescope it resolves into one of the most magnificent double stars in the sky - a pair of golden yellow stars! They orbit their common centre of gravity every 600 years. This lovely pair of orange giants are 170 light years away.
Leo also hosts two pairs of Messier galaxies which lie beneath its belly. The first pair lie about 9 degrees to the west of Regulus and comprise M95 (to the east) and M96. They are almost exactly at the same declination as Regulus so, using an equatorial mount, centre on Regulus, lock the declination axis and sweep towards the west 9 degrees. They are both close to 9th magnitude and may bee seen together with a telescope at low power or individually at higher powers. M65 is a type Sa spiral lying at a distance of 35 millin klight years and M66, considerably bigger than M65, is of type Sb. Type Sa spirals have large nuclei and very tightly wound spiral arms whilst as one moves through type Sb to Sc, the nucleus becomes smaller and the arms more open.
The galaxies M65 and M66
M65 - Type Sa spiral, 9.3 magnitude M66 - Type Sb spiral, 8.9 magnitude
The second pair of galaxies, M95 and M96, lie a further 7 degrees to the west between the stars Upsilon and Iota Leonis. M95 is a barred spiral of type SBb. It lies at a distance of 38 million light years and is magnitude 9.7. M96, a type Sa galaxy, is slightly further away at 41 million light years, but a little brighter with a magnitude of 9.2. Both are members of the Leo I group of galaxies and are visible together with a telescope at low power.
The galaxies M95 and M96
M95 - Type SBb spiral, 9.7 magnitude M96 - Type Sa spiral, 9.2 magnitude
There is a further ~9th magnitude galaxy in Leo which, surprisingly, is in neither the Messier or Caldwell catalogues. It lies a little below lambda Leonis and was discovered by William Herschel. No 2903 in the New General Catalogue, it is a beautiful type Sb galaxy which is seen at somewhat of an oblique angle. It lies at a distance of 20.5 million light years.
The 8.9th magnitude, type Sb, Galaxy NGC2903
The constellation Virgo
Virgo
Virgo, rising in the east in late evening 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 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
