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« April 2017

The Night Sky May 2017

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.


The author's: Astronomy Digest

which, over time, will provide useful and, I hope, interesting articles for all amateur astronomers.   A further aim is to update and add new material to link with the books recently published by Cambridge University Press and which are described on the home page of the digest.

May 2017: A tale of two scopes

                    Imaging and enhancing constellation images.

                    The iOptron MiniTower range of alt/az mounts.

Image of the Month


The galaxy UGC1259
Image NASA, ESA, Hubble Space Telescope.

The spiral galaxy NGC 4302, seen left, lies at a distance of 55 millian light-years away in Coma Berenices.   Seen side on, it is a member of the Virgo Galaxy Cluster and spans some 87,000 light years across - a little smaller than our own Milky Way. Its companion, NGC 4298, is tilted more nearly face on and is similar to M33 in our local group of galaxies.

Highlights of the Month

May - a great month to view Jupiter.

Jupiter imaged by Damian Peach

This is a great month to observe Jupiter which came into opposition on April 7th so, during May, will be visible in the south during the evening.   It is moving down the ecliptic and lies in Virgo.   It now reaches an elevations of ~36 degrees when crossing the meridian.   An interesting observation is that the Great Red Spot appears to be diminishing in size.   At the beginning of the last century it spanned 40,000 km across but now appears to be only ~16,500 km across - less than half the size.   It used to be said that 3 Earths could fit within it, but now it is only one.   The shrinking rate appears to be accelerating and observations indicate that it is now reducing in size by ~580 miles per year.   Will it eventually disappear?

  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"

Jovian Features
Features in Jupiter's atmosphere - December 2013.

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 evening times during May to observe the Great Red Spot which should then lie on the central meridian of the planet. The times are in UT.

2nd   22.33         21st 23:13

5th   20:02         24th 20:42

7th   21:40         26th 22:41

9th   23:18         27th 23:23

12th 20:48         28th 23:59

14th 22:46         31st 21:29

19th 21:34

May 4/5th - after midnight: The Moon occults the double star 49 Leonis

The Moon occults 49 Leonis.
Image: Stellarium/IM

Just after 00:20 BST, the dark limb of the Moon will occult the double star 49 Leonis (magnitudes +5.8 and +7.9 separated by 2 arcseconds).   As a result, the starlight will take longer to be extinguished than from a single star.   If the seeing were good, it might be possible to split the pair using a high magnification and see each component disappear.

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 only be glimpsed in the pre-dawn sky in the south-east around 90 minutes before dawn.   Sadly, this year the peak is when the Moon is coming towards full - but happily low on the western horizon - so there will be some moonlight to hinder our view.

May 7th - evening: The Moon and Jupiter

The Moon and Jupiter
Image: Stellarium/IM

This evening the Moon, three days before full, will pass just 1.5 degrees above Jupiter.

15th May - evening:Observe the Galilean Satellites.

Jupiter's Moons
Jupiter's Galilean Satellites
Image: Stellarium/IM

If clear on the evening of the 15th, and using a small telescope, one could observe the 4 Gallilean Moons lined up on one side of the giant planet.

22nd May - dawn:Venus and a thin crescent Moon

Venus and a crescent Moon.
Image: Stellarium/IM

Before dawn on the 22nd, Venus will be seen over to the left of a very thin waning crescent Moon.

22nd to 31st May - all night:Observe Comet 2015 V2 (Johnson)

Comet Johnson
Comet 2015 V2 (Johnson)
Image: Stellarium/IM

During the last 10 days of May, with no Moonlight to hinder our view, binoculars or a small telescope could be used to spot Comet Johnson as it moves down through the constellation Bootes closing in on the bright star Arcturus.   It might reach magnitude +6 so should be easily visible with binoculars.   The chart shows its position during this time.

27th May - ~23:20 BST: a shadow transit of Jupiter.

Ganymede's shadow crosses Jupiter.
Image: Stellarium/IM

Starting around 23:20 UT, the shadow cast by Ganymede will begin to pass across the Jovian disk leaving the disk at about 00:11 UT on the 28th.   During this time it might be possible to spot Io moving across the disk with its shadow falling into the disk at ~00:25 UT.

29th to 31st May - after sunset: A crescent Moon passes the Beehive Cluster in Cancer on its way towards Regulus in Leo.

The crescent Moon en-route to Regulus.
Image: Stellarium/IM

After sunset on the last three day of the month, one can observe, if clear, a thin waxing crescent Moon passing the Beehive cluster (M44) as it moves up to pass Regulus, in Leo, on the 31st.

May 3rd and 16th, 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

M16, the Eagle nebula, imaged with the Faulkes Telescope

Messier 16 - The Eagle Nebula
Image: Daniel Duggan
Faulkes Telescope North.

The Eagle Nebula, M16, 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 is a region of dust and gas where stars are now forming.   The ultraviolet light from young blue stars is stripping the electrons from hydrogen atoms so this region contains ionized hydrogen and is called an HII region.   As the electrons drop back down through the hydrogen energy levels as the atoms re-form, red light at the H alpha wavelength is emitted.   This "true colour" image is composed of red, green and blue images along with a narrow band H alpha image.   A Hubble image of the central region, called the "Pillars of Creation", has become quite famous but looks green/blue in colour.   This is a false colour image where the H alpha image has been encoded as green!

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 25th May 3rd May 10th May 19th

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 came into opposition on April 7th so, this month, transits in the late evening and is visible rising in the east at dusk.   It is moving in retrograde motion in Virgo initially some 9 degrees over to the right of its brightest star, Spica.   This increases to ~11 degrees as May progresses.   The size of Jupiter's disk decreases slightly from 43.5 to 40.8 arc seconds during May with its magnitude reducing very slightly from -2.4 to -2.3.   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 highlights above.


The planet Saturn. Cassini - Nasa

Saturn. As May begins,Saturn rises rises around 11:30pm BST and will be highest in the pre-dawn sky at ~4am BST.   By the end of May it will rise at ~9:30pm BST and transit at around 2am BST.   Lying in the western part of Sagittarius, its diameter increases from 17.8 to 18.3 arc seconds during the month as it brightness increases slightly from magnitude +0.3 to +0.1.   It will be high enough in the south-east in the hours before dawn to make out the beautiful ring system which, at over 26 degrees to the line of sight, are nearly as open as they ever become.   If only it were higher in the ecliptic; its elevation this year never gets above ~18 degrees and so the atmosphere will hinder our view of this most beautiful planet.   [Note: I have acquired a ZWO Atmospheric Dispersion Corrector which uses two contra-rotating prisms to combat the dispersion of the atmosphere at low elevations.   If imaging Saturn (or Jupiter), Registax 6 has a tool to align the red, green and blue colour images to largely remove the dispersion from the image.]


Messenger image of Mercury Nasa

Mercury is lost in thr glare of the Sun this month so cannot be observed.


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

Mars. Mars lies in Taurus initially making a shallow triangle with Aldabaran to its lower left and the Pleiades cluster to its lower right.   In early April, Mars has an elevation of ~11 degrees above the western horizon at sunset, but this reduces to ~5 degrees by month's end when Mars will be lost in the Sun's glare.   It will then be lost from view all summer as it passes behind the Sun.   By month's end it will lie some 6.5 degrees over to the left of Alnath, Beta Tauri.   Its brightness falls slightly during the month from magnitude +1.6 to +1.7 whilst its angular diameter falls from 3.9 to 3.7 arc seconds.   No details would be expected to be seen on its salmon-pink surface.


Venus showing some cloud structure

Venus rises in the east in the morning twilight on the first of the month and then climbs a little higher each morning as May progresses.   On May 1st, the disk, forming a crescent 38 src seconds high, is just 27% lit shining with a magnitude of -4.7 - its maximum brightness.   By the end of the month, Venus shines at magnitude -4.5 with its angular size reduced to 25 arc seconds and its illuminated fraction increased to 48%.   It is then close to its greatest elongation from the Sun of 46 degrees which it will reach on June 3rd.   But, due to the shallow angle that the ecliptic makes to the horizon at this time of the year, it will then only have an elevation of ~16 degrees at sunrise.   In daytime when still high in the sky it can be imaged in the infrared as the blue light from the sky is filtered out.   The astronomy digest article on imaging the Moon and planets in the infrared shows how Venus looked on the 5th of January 2017.

See highlight above.

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