The Night Sky May 2013
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
Hubble Image of the Horsehead Nebula
NASA,ESA and Hubble Heritage Team (STSci/AURA)
An infrared image of the Horsehead Nebula in Orion taken by the Hubble Space Telescope. It is a dark molecular cloud about 1,500 light years away. It is normally seen in silhouette against the light emitted by hydrogen gas in the region excited by ultra-violet light from the nearby star Sigma Orionis.
Highlights of the Month
April - Saturn, the second of two good months
Saturn reached opposition on the 28th April, so this is the second of two good two months to observe it. It will begin the month lying 1,340 million km from the Sun some nine times further away than the Earth and shine at magnitude +0.3. Its disk, 18 arc seconds across, is surrounded by its beautiful ring system that extends over 43 arc seconds.
To find it in the sky, follow the arc of the Plough's handle downwards to first find the orange star Arcturus and continue down to find the white, first magnitude star, Spica, in Virgo. Saturn, a little brighter than Spica, lies over to its left, initially in the constellation Libra, and will appear slighly yellow in colour. It moves closer to Spica as it crosses into Virgo on the 13th of May.
Held steady, binoculars should enable you to see Saturn's brightest moon, Titan, at magnitude 8.2. A small telescope will show the rings with magnifications of x25 or more and one of 6-8 inches aperture with a magnification of ~x200 coupled with a night of good "seeing" (when the atmosphere is calm) will show Saturn and its beautiful ring system in its full glory.
As Saturn rotates quickly with a day of just 10 and a half hours, its equator bulges slightly and so it appears a little "squashed". Like Jupiter, it does show belts but their colours are muted in comparison.
The thing that makes Saturn stand out is, of course, its ring system. The two outermost rings, A and B, are separated by a gap called Cassini's Division which should be visible in a telescope of 4 or more inches aperture if seeing conditions are good. Lying within the B ring, but far less bright and difficult to spot is the C or Crepe Ring.
Due to the orientation of Saturn's rotation axis of 27 degrees with respect to the plane of the solar system, the orientation of the rings as seen by us changes as it orbits the Sun and twice each orbit they lie edge on to us and so can hardly be seen. This last happened in 2009 and they are now opening out, currently at an angle of 18 degrees to the line of sight. The rings will continue to open out until May 2017 and then narrow until March 2025 when they will appear edge-on again.
See more of Damian Peach's images: Damian Peaches Website"
May 6th before dawn: The Eta Aquarid Meteor Shower
Looking East-Southeast well before dawn on the morning of May 6th and given a good low horizon in that direction you may be able to spot some of the meteors that are part of the Eta Aquarid meteor shower. A thin waning crescent Moon should not hide many of the ~10 meteors per hour that might be seen from our northerly latitude. The Eta Aquarids result from dust particles that were released from Comet Halley in an eruption as it neared the Sun some 4,000 years ago.
May - all night: Comet PanSTARRS
There is still a chance to spot Comet PanSTARRS which is now visible all night passing across from Cassiopeia towards Polaris. But, as it receeds further from the Sun, it is fading fast and so the best chance of observing it will be at the beginning of the month. Comet PanSTARRS was discovered some two years ago when it lay between the orbits of Saturn and Jupiter - having a brightness of just 19th magnitude. It is named after the Panoramic Survey Telescope and Rapid Response System. It reached perihelion, when closest to the Sun, on March 10th at a distance from the Sun of just 0.3 AU and so inside the orbit of Mercury. Its magnitude is now dropping rapidly (around magnitude +7 at the beginning of May)so binoculars will be needed to spot it. The chart shows its position during the month as it moves from Cassiopeia into Ursa Minor.
The image at right was taken on the 28th March from Cheshire by Andrew Greenwood and is a stack of 24 individual images taken with a Nikon D5100 DSLR.
May 13th: PanSTARRS passes close to the 3.2 magnitude star Gamma Cephei.
May 31st: PanSTARRS is 5 degrees below and to the right of Polaris
May - Comet Lemmon enters our skies
A second comet will grace our skies this May as Comet Lemmon enters our northern skies moving up to the left of the square of Pegasus with a likely magnitude of +6.5. It will be seen in the pre-dawn sky and perhaps lost in the Sun's glare until later in the month when it will be seen against a darker sky, but its magnitude will have then dropped to ~+8. On the 11th it will lies just to the left of the lower left star of the great square moving northwards until, on the 30th, it will be close to the top left of the square just a few degrees to the left of Alpharatz, Alpha Andromedai. Comet Lemmon exceeded expectations in the southern hemisphere reaching a magnitude of +4.7 in mid-March and showing a slender green tail.
May 24th/25th - A "Megamoon"
As the Moon rises on the late evening of the 24th it will be close to perigee - its closest distance to the Earth - and so will have an angular size close to 33 arc minutes. Its diameter will then be 12% greater than when at apogee and so will appear very large and bright as it rises above the horizon.Full Moon actually occurs on the morning of the 25th and there is a very minor penumbral lunar eclipse. The Moon's limb comes within the Earth's penumbral shadow for about one hour around 5am BST as the Moon is setting in the west. Not an eclipse to get up for!
May 24th to 28th - A close grouping of Mercury, Venus and Jupiter.
Towards the latter part of the month, Jupiter is dropping towards the horizon whilst Venus and Mercury are rising into the evening sky. The three planets come together from the 24th to the 28th and will form a tight equilateral triangle on the evening of the 26th. They will be best seen around 22:00 BST in the north north-west after Sunset. Binoculars will encompass all three but do not attempt to use them until after the Sun has set. Venus will appear the brightest followed by Jupiter and then Mercury. The diagram shows how they will appear on the 26th of the month.NB: The sky brightness in the chart has been reduced and the planets will not appear so obviously to your eyes!
May 17th Evening: The Hyginus Rille
This evening, should it be clear is a superb time to view the Hyginus Rill as it will lie close to the terminator. For some time a debate raged as to whether the craters on the Moon were caused by impacts or volcanic activity. We now know that virtually all were caused by impact, but it is thought that the Hyginus crater that lies at the centre of the Hyginus Rille may well be volcanic in origin. It is an 11 km wide rimless pit - in contast to impact craters which have raised rims - and its close association with the rille of the same name associates it with internal lunar events. It can quite easily be seen to be surrounded by dark material. It is thought that an explosive release of dust and gas created a vacant space below so that the overlying surface collapsed into it so forming the crater.
M109 imaged with the Faulkes Telescope
The Barred Spiral galaxy M109, imaged by Daniel Duggan.
This image was taken using the Faulkes Telescope North by Daniel Duggan - for some time a member of the Faulkes telescope team. It shows the barred spiral galaxy M109 that lies at a distance of 83 million light years in the constellation of Ursa Major. It is the brightest galaxy in the Ursa Major group of some 50 galaxies. Our own Milky Way galaxy is now thought to be a barred spiral like M109.
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 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 10th||May 18th||May 25th||May 2nd and 31st|
Some Lunar Images by Ian Morison, Jodrell Bank Observatory: Lunar Images
A World Record Lunar Image
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 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.
Jupiter, in the constellation of Taurus. the Bull, will still be visible in the west after sunset moving eastwards across the sky but its low elevation will hamper our viewing. Shining at magnitude -2, it starts May lying between the horns of the Bull some 9 degrees above the star Aldebaran, the eye of the Bull. During the month its angular diameter drops slightly from 33.6 to 32.4 arc seconds but a small telescope will still show some details with the bright zones and darker bands crossing the disk and up to four Gallilean moons visible as they weave their way around the giant planet.
Saturn, lying in Libra as May begins, reached opposition on the 28th April so will be visible all night and be due south around 00:00 UT in early May. It crosses into Virgo on the 13th as it moves westwards in retrograde motion. Saturn's magnitude falls fractionally during the month, from +0.1 to +0.3 magnitudes, whilst its angular size decreases from 18.8 to 18.5 arc seconds. The good news is that the rings have now opened out to ~18 degrees from the line of sight and will be at their best for 6 years! (The observed tilt has actually very slightly reduced during the last couple of months.) Around opposition, the rings will extend 43 arc seconds across and 13 arc seconds in width. We are now observing the planet's southern hemisphere whilst much of the northern hemisphere will be hidden by the rings. With a small scope one should now be able to spot Cassini's Division within the rings if the "seeing" is good along with Saturn's largest Moon, Titan. Saturn is now lying in the more southerly part of the ecliptic so its elevation does not get that high when seen from our northern latitudes (28 degrees at transit) and, sadly, this will get worse for quite a number of years.
See highlight above.
Mercury, passes behind the Sun (superior conjunction) on May 11th, so will not be visible until the 19th when it joins Jupiter and Venus in the evening sky. The three planets then form a thirteen degree long line with Mercury just 3 degreees above the horizon, Venus some 4 degrees to its upper left and Jupiter a further 9 degrees on. Even though Mercury will shine at magnitude -1.4, binoculars will be needed to spot it. As May progresses, Mercury climbs higher (but becomes fainter) and Jupiter drops lower towards the horizon. From the 24th to 29th, the three planets form a "trio" with all three planets within a 5 degree circle so visible together using binoculars. The three planets will lie 6 degrees above the horizon half an hour after sunset. On the 26th they will lie within a circle of 2.5 degrees making a superb imaging opportunity.
See highlight above.
Mars passes behind the Sun on April 18th and will not be visible for several months until it appears in the pre-dawn sky.
Venus, shining at magnitude -3.9, emerges from behind the Sun in the second week of May and rises to join Mercury and Jupiter in the evening sky after sunset. The three planets form a close trio from the 24th to the 28th. Venus spans 10 arc seconds and is nearly full phase in mid May with its phase dropping to 96% by months end.
See highlight above.
Find more planetary images and details about the Solar System: The Solar System
The evening May Sky
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 - 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.
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
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 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.
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 constellation 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.
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 constellation 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.
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).
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.
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.