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« April 2016

The Night Sky May 2016

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.

Cambridge University Press has recently published two books by the author. An Amateurs Guide to Observing and Imaging the Heavens is a handbook aimed to bridge the gap between the beginner's books on amateur astronomy and the books which cover a single topic in great detail.   Stephen James O'Meara and Damian Peach have both given it excellent reviews. 'A Journey through the Universe' covering our current understanding of the Universe has been given a very nice review by our Astronomer Royal, Martin Rees.

Two great highlights this month: the transit of Mercury on the 9th and the opposition and closest approach of Mars on the 22nd and 29th of May.

Image of the Month


Hubble Image of the Bubbel nebula NGC 7635

Image:AURA/STScI, ESA, NASA, Hubble Heritage Team

The seven light-year diameter Bubble Nebula is the result of a fierce solar wind ejected from the O-type star above and to the left of its centre.   The star is several hundred thousand times more luminous that our Sun and 45 times more massive.   The nebula lies some 7,100 light years distant in the Constellation Cassiopeia.   This image was taken to commemorate the 26th anniversary of Hubble's launch in 1990.

Highlights of the Month

May 9th - the Transit of Mercury across the face of the Sun

Mercury Transit
The transit of Mercury
Image:Eclipsophile: Jay Anderson and Jennifer West.
On May the 9th, we will, if clear in the UK, be able to witness the complete passage of Mercury's disc across the face of the Sun.   The transit begins soon after 11 hours UT, the midpoint of the transit is at 14:58 UT and Mercury leaves the Sun's disk at 18:42 UT - a total time of 7 and a half hours.   This is Mercury' first transit since 2006 and the next will occur on November 11th 2019 but will not be so easily visible from the UK.   These are three of the 13 or 14 Mercury transits that occur each century.

Mercury's black disk will appear only 10 arcseonds across so binoculars or a telescope will be needed to observe the transit.   If direct viewing is to be made a suitable solar filter must be placed in front of the objective(s).   Filters made using Baader Solar Film are probably best.   Alternatively, an image of the Sun can be projected onto white card using a small telescope or half binocular.   An all metal eyepiece is needed to prevent heat damage and its probably best to limit the aperture to ~1 inch across using a cardboardmask.   Always take very great care when viewing the Sun - it is the only astronomical object that can harm us!

  At first glance Mercury's disk might, at just 1/200th of the Suns width, appear as a sunspot, but it will be precisely round, be even darker, will lack a grey penumbra and - of course - it will be moving across the Sun' disk.   It will be interesting to watch the ingress and exit of Mercury's disk taking 3 minutes and 12 seconds to do so.   Let's hope for clear skies!

May 22nd to June 8th: Mars at its best for 11 years.

Mars at opposition and closest approach
Image: Stellarium/IM
Mars reaches opposition - that is when the Earth lies between the Sun and Mars and when it will be approximatly due south at midnight (UT) or 1 am (BST) - on the 22nd of May, so it will be visible for most of the hours of darkness.   However, it will actually be closest to the Earth and so have its greatest angular size of 18.6 arc seconds some 8 days later on the 30th of May.   The angular size at closet approach varies due to the ellipticity of the orbit of Mars (and to a far lesser extent to that of the Earth)and will reach 26 arc seconds during 25,695 AD.   At closest approach in 2003, Mars reached an angular size of 25.1 arc seconds, its largest angular diameter for 60,000 years.   In July 2018 it will reach 24.2 arc seconds across but for both this opposition and that in 2018, Mars will be very low in the ecliptic and hence at low elevation so that the atmosphere will limit our views of the red (actually salmon pink) planet.   Happily, it will be higher in the sky at the opposition of 2020.

To find what should be visible at any time, one can use the Sky & Telescope application: http://is.gd/marsprofiler.

May: Look for the Great Red Spot on Jupiter

Great Red Spot
Observe the Great Red Spot
Image: NASA

This list gives some of the best late evening times (in UT) during May to observe the Great Red Spot (which is unusually vivid this year) which should then lie on the central meridian of the planet.

3rd   00:22         29th 21:45

5th   21:52         31st 23:24

10th 21:01        

12th 22:39        

17th 21:48        

19th 23:27        

24th 22:36

May 5th and 6th before dawn: The Eta Aquarid Meteor Shower

The Eta Aquarid Meteor Shower
Image: Stellarium/IM

The Eta Aquarids are one of the finest meteor showers that can be seen from the southern hemisphere, but, in the northern hemisphere, may be glimpsed in the pre-dawn sky in the south-east around 90 minutes before dawn.   Pleasingly, this year the peak corresponds to new Moon so there will be no moonlight to hinder our view.

May 7th - one hour before sunrise: Saturn, Mars and Antares

Saturn and Mars
Saturn and Mars close to Antares
Image: Stellarium/IM

Looking to the South-Southwest in the hours before sunrise, Saturn, above, and Mars, to the upper right, can be seen close to Antares in Scorpius.

May 7th - after sunset: a very thin waxing crescent Moon

Crescent Moon
A 1% illuminated crescent Moon
Image: Ian Morison

If clear at sunset, and given a low horizon in the West-Northwest, you may be able to spot a very thin waxing crescent Moon just 1% illuminated.   Binoculars may be needed, but please do not use them until after the Sun has set.   You may be able to observe the major part of the Moon's surface illuminated by light reflected from Earth - called Earthshine - as seen in the accompanying image taken by the author at the Isle of White Star Party.

May 14th and 27th, 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 Rille
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
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

3rd Quarter 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 6th May 13th May 21st May 29th

Some Lunar Images by Ian Morison, Jodrell Bank Observatory: Lunar Images

A World Record Lunar Image

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
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
A montage of the Solar System. JPL / Nasa


A Cassini image of Jupiter . Nasa

Jupiter is now a little past its best, but still stands out high in the South at nightfall.   Its brightness falls slightly from magnitude -2.3 to -2.1 whilst its angular size drops from 41 to 37 arc seconds during the month.   Jupiter spends the month below the hindquarters of Leo, halting its retrograde motion westwards across the sky on May 9th.   Jupiter sets around 4 am as May begins but by 2 am by month's end.   With a small telescope one should be easily able to see the equatorial bands in the atmosphere, sometimes the Great Red Spot and up to four of the Gallilean moons as they weave their way around it.

See highlight above.


The planet Saturn. Cassini - Nasa

Saturn rises in the late evening about 30 minutes after Mars as May begins.   Its brightness increases slightly from +0.2 to 0.0 magnitudes during the month whilst its angular size grows to 18.4 arc seconds.   Saturn's rings are tilted by 26 degrees from the line of sight - almost as open as they ever get - and span 42 arc seconds.   It is moving towards opposition on the night of June 2nd.   Saturn forms a triangle with Mars and Antares throughout the month, separated from Mars by 8 degrees as May begins and by 15 degrees at month's end.   As Saturn moves slowly across the heavens, it stays at a near constant distance from Antares.

See the highlight above.


Messenger image of Mercury Nasa

Mercury. The top highlight this month is Mercury's transit across the face of the Sun on May the 9th, but otherwise it will be too dim and low above the horizon to be seen.

See highlight above.


Mars showing Syrtis major.
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa

Mars reaches its closest point to the Earth on May 29th for 11 years with an angular size then of 18.6 arc seconds.   It starts the month with an angular size of 16 arc seconds and a magnitude of -1.5, brightening until it reaches its peak of -2.1 magnitudes so equalling the magnitude of Jupiter for a few day.   Mars, in retrograde motion westwards across the sky, lies low in Scorpius beginning the month 5 degrees north of Antares and passing between Beta and Delta Scorpii on the 19th as it moves towards Libra.

See highlight above.


Venus showing some cloud structure

Venus is heading towards superior conjunction with the Sun (on the far side) on June 2nd and is not visible during May.

Radar Image of Venus
Radar image showing surface features

Find more planetary images and details about the Solar System: The Solar System

The Stars

The evening May Sky

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 - 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


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.

M65 and M66
The galaxies M65 and M66
M65 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.

M95 and M96
The galaxies M95 and M96
M95 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, 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.

M87 MERLIN images
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.

The Sombrero Galaxy
M104 - The Sombrero Galaxy

The constellation Ursa Major

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
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.

Owl Nebula Owl Nebula
M97 - The Owl Planetary Nebula Lord Rosse's 1848 drawing of the Owl Nebula