Highlights of the Month
Mars - Mars after Opposition.
Image NASA.
Mars, lying above Spica in Virgo, reached opposition on April 8th when its magnitude was -1.5 and its angular diameter 15.1 arc seconds. At the beginning of May it still shines at magnitude -1.2 and its angular size is 14.5 arc seconds so it is still very worth while observing. Due to the fact that Mars, and to a lesser extent, the Earth have elliptical orbits, its distance from us at opposition can vary from ~54 to 102 million km. As a result the angular size will vary from ~13 to 25 arc seconds - a major difference. The angular size at opposition is now increasing to reach 18.6 arc seconds in May 2016 and 24.31 arc seconds in July 2018. Sadly, this year, Mars' elevation when on the meridian will only be ~30 degrees, so the atmosphere will limit our view somewhat but given a night of good seeing and a small telescope the planet's main features should be seen such as the north polar cap and Syrtis Major - a triangular shaped dark region.
May - a great month to observe Saturn.
Saturn in the evening Sky
Saturn reaches opposition on the 10th of May, so this is a great month 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 +0.1. 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 in Libra down to its lower left 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 22 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"
Saturn imaged in April 2012 by Damian Peach
Early May - it is still worthwhile to view Jupiter.
Jupiter imaged by Damian Peach
Jupiter is now well past opposition but, during the first couple of weeks of May, is still worth observing. Though Jupiter's angular size falls from ~35 down to ~33 arc seconds throughout the month, a small telescope can see lots of details. It is looking somewhat different than in the last few years as the north equatorial belt has become quite broad. The Great Red Spot has recently become more prominent and can be easily seen as a large feature in the South Equatorial Belt.
The features seen in the Jovian atmosphere have been changing quite significantly over the last few years - for a while the South Equatorial Belt vanished completely (as seen in Damian's image) but has now returned to its normal wide state. The diagram on right shows the main Jovian features as imaged by the author at the beginning of December 2012.
The image by Damian Peach was taken with a 14 inch telescope in Barbados where the seeing can be particularly good. This image won the "Astronomy Photographer of the Year" competition in 2011.
See more of Damian Peach's images: Damian Peaches Website"
Features in Jupiter's atmosphere - December 2013.
May : Follow a comet as it passes below the Plough.
Comet C/20112 K1
Image: Stellarium/IM
During the dark nights of May - at the beginning and end when the Moon is near new - it should be possible to spot comet C/20112 K1, Pan STARRS, as it passes below the Plough shining at magnitude 7 or 8. Good evenings to observe it are on May 1st and 2nd when it is down to the right of the left hand star in the Plough's handle, on the 18th and 19th when it lies very close to Chi Ursa Majoris and 26th and 27th when it lies adjacent to Psi Ursa Majoris.
May 3rd and 4th - 1 hour after sunset: Jupiter and a crescent Moon
Jupiter and a crescent Moon
Image: Stellarium/IM
After sunset during the first few days of May, Jupiter will be seen in the west above a waxing crescent Moon.
May 6th before dawn: The Eta Aquarid Meteor Shower
The Eta Aquarid Meteor Shower
Image:Stellarium/IM
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. The Moon, just before first quarter, will not lie in the sky and so will not hide any 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 11th - one hour after sunset: Mars and a waxing Moon.
Mars and a waxing Moon.
Image: Stellarium/IM
Looking southeast around one hour after sunset the Moon will pass below Mars in Virgo. They are closest on the 11th when Mars is ~ 6 degrees above and to the right of the Moon.
May 13th and 14th - one hour after sunset: Saturn and a full Moon.
Saturn and the Moon
Image: Stellarium/IM
Looking southeast around one hour after sunset the full Moon will lie about 5 degrees below Saturn, which is shining at magnitude +0.15 in Libra.
May 30th - after sunset: Mercury and a thin crescent Moon.
Mercury near a thin crescent Moon.
Image: Stellarium/IM
Looking just north of west around one hour after sunset Mercury will be seen just above the horizon up to the right of a thin crescent Moon. Jupiter will lie up to the left of them both.
May 6th and 7th, evening: The Hyginus Rille
Hyginus Rille location: IM.
These evenings, should it be clear, are 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.
Hyginus Crater and Rille
M109 imaged with the Faulkes Telescope
Messier 109
Image: Daniel Duggan
Faulkes Telescope North.
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
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 28th |
May 6th |
May 14th |
May 21st |
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 is high in the south western sky at sunset as it nears the end of an excellent apparition whilst Mars is closest to us on April 14th.
Jupiter
A Cassini image of Jupiter . Nasa
Jupiter. As May begins, Jupiter is still at an elevation of 45 degrees in the western sky an hour after sunset. It is, however, now past its best and fading from -2.0 to -1.9 during the month whilst its angular diameter shrinks from 35 to 33 arc seconds. By month's end it will be only ~20 degrees above the horizon after sunset and sets around 11 pm (BST). Jupiter is lying in the constellation Gemini and starts the month two degrees north of the 4th magnitude star Mekbuta, Zeta Geminorum. It is moving eastwards across the sky towards Castor and Pollux passing within half a degree north of the star Wasat, Delta Geminorum, on May 22nd. With a small telescope you can observe the 4 Gallilean moons as they weave there way around it and, at times, be also able to pick out the Great Red Spot visible as an indentation of the South Equatorial belt.
See the highlights above.
Saturn
The planet Saturn. Cassini - Nasa
Saturn comes to opposition on May 10th when it rises just before sunset and sets just after sunrise. Lying in Libra, it is shining with a magnitude of +0.1. Its disk has a diameter of 18.6 arc seconds. Saturn began its retrograde motion across the sky on March 6th is now moving slowly westwards in Libra towards the star Alpha Librae. The good news is that the rings (with a diameter of ~40 arc seconds) have now opened to around 22 degrees from the line of sight so presenting a magnificant view. With a small telescope one should be able to spot the Cassini Division that lies between the A and B rings when seeing conditions are good. Sadly for those of us in the northern hemisphere, Saturn is now lying in the more southerly part of the ecliptic so, even when due south around midnght (UT) does not get that high in the sky. Even worse, this will not improve for many years to come.
See highlights above.
Mercury
Messenger image of Mercury Nasa
Mercury, has its highest apparition in the evening sky this year. As May begins it is very low above the horizon in the western sky in the twilight but, each evening that follows, will appear a little higher in the sky. May the 16th to 28th is the best time to observe it when it will be ~15 degrees above the north-western horizon at sunset and still at ~10 degrees elevation in the latter pasrt of twilight. On May 25th when at greatest eastern elongation and at an angle of 23 degrees from the Sunit will set nearly two hours after sunset and will shine at magnitude +0.4 with its 8 arc second crescent disk being 40% illuminated. At the end on May, still more than 5 degrees above the horizon an hour after sunset, it brightness will have faded to just +1.2.
See highlight above.
Mars
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa
Mars. Following its opposition last month, Mars is now receding rapidly and so will dim from magnitude -1.2 to -0.5 during the month. As it does so, its angular size will shrink from 14.5 down to 11.8 arc seconds so its best to observe it early in the month if the weather allows. Mars halts its retrograde motion westwards in the sky on May 21st so is not moving quickly relative to the stars, staying close to Porrima, Gamma Virginis, in Virgo. It will be highest in the sky at around 11 pm (BST) as May begins.
See highlight above.
Venus
Venus showing some cloud structure
Venus, shining at magnitude ~-4.0 during the month, lies in the southern part of Pisces and will be seen ~12 degrees above the eastern horizon half an hour before sunrise. Its disk, now showing a gibbous phase as it moves beyond the Sun drops in angular size from 17 to 15 arc seconds but, at the same time the percentage of the disk which is illuminated increases from 67 to 77%. As a result the effective area reflecting the sun's light stays almost constant so there is only a drop of 0.1 magnitudes in brightness.
See highlight above.
Radar image showing surface features
Find more planetary images and details about the Solar System: The Solar System
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
