The Night Sky April 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
Curiosity - self portrait
NASA, JPL-Caltech, MSSS - Panorama by Andrew BodrevThe remarkable image shows Curiosity in the Yellowknife Bay region of Mar's Gale Crater. In front of the rover is seen an area where the overlying dust has been brushed away - the site of a sample collection hole 1.6 cm in diameter.
Highlights of the Month
April - Saturn, the first of two good months
Saturn reaches opposition on the 28th April, so this is the first of two good two months to observe it. It will then lie 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 just to its left in the constellation Libra and will appear slighly yellow in colour.
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"
April - after sunset: Comet PanSTARRS
There is still a chance to spot Comet PanSTARRS 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 on the 21st March was +2.3 and, as April begins is predicted to be ~ +3.6. The chart shows its position during the month as it moves from Andromeda into Cassiopeia. It will be low above the horizon so you will need to get to a high observing location with an unobstructed view to the north-west. A great imaging opportunity will occur on the April the 4th and 5th when it passes close to M31,the Andromeda galaxy
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. The comet is now seen against a darker sky so that stars are visible and more of the tail can be imaged in comparison to my image in last month's Night Sky. As the comet has now moved towards the north, the tail is now pointing to the right rather than to the left as on the 13th March image.
April 1st to 6th: PanSTARRS passes just to the west of M31, the Andromeda galaxy,
April 23rd: PanSTARRS, now in Cassiopeia, passes close to the +6.5 magnitude open cluster NGC 129.
April 26th PanSTARRS passes close to the open cluster NGC 102.
April - Jupiter is still worth observing
Though now past its best, Jupiter is still worth observing in the south-western sky after sunset. Now moving eastwards, still lies in Taurus and can be seen in the west after sunset. It is looking somewhat different than in the last few years as the north equatorial belt has become quite broad. The Great Red Spot is currently a pale shade of pink but can be easily seen as a large feature in the South Equatorial Belt. After its apparition next year it will be moving towards more southerly parts of the ecliptic so will be at lower elevations when crossing the meridian and will thus be seen through thicker layers of the atmosphere.
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 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"
April: Look for the Great Red Spot on Jupiter
This list gives some of the best evening times during April to observe the Great Red Spot which should then lie on the central meridian of the planet.
2nd 20:53 24th 19:12
4th 22:32 26th 20:52
April 14th - The Moon and Jupiter in Taurus.
After sunset on the 13th and seen in the western sky, a thin crescent Moon will join Jupiter and the Hyades and Pleiades clusters in Taurus.
April 25th - A partially ecliped full Moon near Saturn
This evening, the full Moon is partially eclipsed as the extreme northern edge is touched by the Earth's shadow with its upper half appearing darker than the lower half. Mid eclipse is at 21:00 BST.
April 30th - Asteroid Vesta close to M35 in Gemini.
Shining at magnitude +8.4, the minor planet 004, Vesta, should be visible close to the open cluster M35 in Gemini low in the west-northwest.
April 20th: Two Great Lunar Craters
Two great Lunar Craters: Tycho and Copernicus
This is a great night to observe two of the greatest craters on the Moon, Tycho and Copernicus, as the terminator is nearby. Tycho is towards the bottom of Moon in a densely cratered area called the Southern Lunar Highlands. It is a relatively young crater which is about 108 million years old. It is interesting in that it is thought to have been formed by the impact of one of the remnents of an asteroid that gave rise to the asteroid Baptistina. Another asteroid originating from the same breakup may well have caused the Chicxulub crater 65 million years ago. It has a diameter of 85 km and is nearly 5 km deep. At full Moon - seen in the image below - the rays of material that were ejected when it was formed can be see arcing across the surface. Copernicus is about 800 million years old and lies in the eastern Oceanus Procellarum beyond the end of the Apennine Mountains. It is 93 km wide and nearly 4 km deep and is a clasic "terraced" crater. Both can be seen with binoculars.
A Messier Object imaged with the Faulkes Telescope: Messier 27 - The Dumbell Nebula
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 resulting 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 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|
|April 10th||April 18th||April 25th||April 3th|
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. Shining at magnitude -2.1, it starts April lying just 5.5 degrees above the star Aldebaran, the eye of the Bull. During the month its angular diameter drops slightly from 35.8 to 33.6 arc seconds so even a small telescope will still show plenty of detail 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. The times given in the highlight above will tell you when the Great Red Spot is visible in the evening but there are fewer opportunities now and, as the disk shrinks, it will be harder to see.
See highlights above.
Saturn, lying in Libra, rises about half an hour after nightfall as April begins and so will transit before dawn at an elevation of 25 degrees at 02:00 UT It reaches opposition on the 28th April so will then be visible all night and be due south around 00:00 UT. Its magnitude brightens during the month,from +0.3 to +0.1 magnitudes, whilst its angular size increases from 18.6 to 18.9 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. Saturn, in Libra, is now in retrograde motion and so moving westwards against the stars with its distance from nearby Alpha Librae (to its lower left) slowly increases from 5.5 to 7.5 degrees. 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 few years.
See highlight above.
Mercury, reached greatest western elongation (when it is furthest from the Sun in angle) on the 31st of March. However this is not a good apparition as the ecliptic at dawn makes a very shallow angle to the horizon at this time of year. As a result, Mercury will be very low above the horizon in the east-southeast as dawn breaks and binoculars will be needed to spot it during the early part of April. But please do not use them when the Sun has risen!
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 reached superior conjunction on March 28th and so, on the far side of the Sun, will not be visible for most of the month. It might just be seen, very low in the west-northwest, about 20 minutes after sunset at the end of the month but binoculars will be needed to spot it even though its magnitude will be -3.9. Do not search for it until after the Sun has set!
Find more planetary images and details about the Solar System: The Solar System
The mid evening April Sky
This map shows the constellations seen in the south in mid-evening.
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. It is well worth observing with binoculars to see the Beehive Cluster at its heart. Below Gemini is the tiny constellation of 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. The constellation Ursa Major is high in the northern sky during the evening this month and 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 main 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.