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« March 2015


The Night Sky April 2015

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 (up to June last year) was published on the 25th of September.   Martin Rees has written a very nice review of it.


Image of the Month

M106

The Galaxy M106


Image:NASA,ESO,NOAJ,Giovanni Paglioli, processing by R. Colommmbari and R. Gendler

This picture of M106 is one of the most stunning astronomical images that I have ever seen.   It is a composite of data from the Subaru Telescope combined with Hubble Space Telescope observations of the galaxy core.   It has been assembled and processed Robert Gendler and colour has been added to the luminance (monochrome) image using a colour image taken by Giovanni Paglioli.

M106 lies in Canes Venatici below the handle of the Plough in Ursa Major.   Its appearance is dominated by blue spiral arms and red dust lanes near the nucleus.   It is the closest example of a Seyfert Galaxy having a very bright central core where it is thought vast amounts of glowing gas is falling inot a super-massive black at its heart.   M106 spans some 60 thousand light years across and lies at a distance of 23.5 million light years.   As its Messier designation implies it can be seen with a small telescope or even large binoculars given a dark sky location.


Highlights of the Month

April - still a great month to view Jupiter.

Jupiter
Jupiter imaged by Damian Peach

This is still a great month to observe Jupiter.   It now lies in Cancer and so is still high in the ecliptic and hence, when due south, at an elevation of ~55 degrees.

  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.





April: 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 April to observe the Great Red Spot which should then lie on the central meridian of the planet.

1st   20:19         18th 19:24

3rd 21:58           20th 21:03

6th   19:28         22nd 22:42

8th   21:06         25th 20:12

10th 22:45         27th 21:51

13th 20:15         30th 19:21

15th 21:54


April 9th: before dawn - the Moon and Saturn

Saturn
The Moon and Saturn
Image: Stellarium/IM

Before dawn on the 9th of the month, Saturn will be seen near a waning gibbous Moon.

April 11th to 13th: 45 minutes after sunset - Venus close to the Pleiades Cluster.

Saturn
Venus and the Pleaides Cluster
Image: Stellarium/IM

After sunset and as darkness falls, Venus will be seen just to the left of the Pleaides Cluster in Taurus.

April 19th: A great observing challenge! Mars, Mercury and a very thin crescent Moon

Mars,Mercury and the Moon
Mars,Mercury and a thin waxing cresent Moon.
Image: Stellarium/IM

After sunset, and given a clear sky and low western horizon, you may be able to see a very thin crescent Moon forming an almost equilateral triangle with Mars (at magnitude 1.4) and Mercury (at magnitude -1.4) as shown on the chart.   Their separations are between 4 and 5 degrees.   The Moon will just under one day old and this is essentially the soonest after New Moon that it is possible to be observed.   Authorities differ, but indicate that the Moon may be seen if the angular separation between the Sun and Moon exceeds 11 or 12 degrees.   After sunset the separation will be 13.5 degrees, so it may be possible.   Binoculars or a small telescope with a low power eyepiece may well be needed.   Please do not use them until after the Sun has set but, then, look up and little to the left of where the Sun dropped below the horizon.


April 21st: Venus, the Moon and the Hyades Cluster

Venus, the Moon and the Hyades cluster
Venus, a waxing cresent Moon and the Hyades Cluster
Image: Stellarium/IM

An hour after sunset Venus will be seen in the west with the waxing crescent Moon just above the star Aldebaran which lies between us and the Hyades cluster in Taurus.


April 26th: Jupiter, in Cancer, above the first quarter Moon

Jupiter above the first quarter Moon
Jupiter above the first quarter Moon
Image: Stellarium/IM

An hour after sunset on the 26th, Jupiter will be seen lying just over 6 degrees above the first quarter Moon.


April 1th and 28th: Two Great Lunar Craters

10thJuly
Tycho and Copernicus: IM.

Two great Lunar Craters: Tycho and Copernicus
This are two good nights 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.

The Alpine Valley
Full Moon showing Tycho's rays: IM

A Messier Object imaged with the Faulkes Telescope: Messier 27 - The Dumbell Nebula

M27 - The Dumbell Nebula
The Dumbell Nebula
Image:Nik Szymanik
Faulkes Telescope North.

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
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
April 18th April 25th April 4th April 12th

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

Jupiter

Jupiter
A Cassini image of Jupiter . Nasa

Jupiter is now two months past opposition and but this is still a good month to observe it - high in the south-western sky during the evening   Its brightness falls slightly from magnitude -2.3 to -2.1 whilst its angular size drops from 41.5 to 38 arc seconds.   Jupiter spends the month in Cancer, hardly moving as it ends its retrograde motion westwards on the 11th of the month and slowly begins its eastwards progress towards Leo.   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.


Saturn

Saturn
The planet Saturn. Cassini - Nasa

Saturn now rises in the evening, earlier each night so that by month's end it rises about 09:30 BST.   Shining at magnitude +0.3 and brightening to +0.1 during the month it lies in Scorpius very close to the left hand star of the 'fan' that marks its head.   Its diameter increases from 17.8 to 18.4 arc seconds as April progresses.   It will be due south in the early hours of the morning at an elevation of ~22 degrees.   The beautiful ring system has now opened out to ~25 degrees - virtually as open as they ever become.   If only it were higher in the ecliptic; its elevation never gets above ~22 degrees and so the atmosphere will hinder our view of this most beautiful planet.


See highlight above.


Mercury

Mercury.
Messenger image of Mercury Nasa

Mercury passes behind the Sun (superior conjunction) on the 10th of April, so cannot be seen until later in the month.   By the 19th, shining at magnitude -1.4, it should become visible very low in the west-northwest about 45 minutes after the Sun has set.   It will gradually rise higher in the sky until the 7th of May when it reaches its greatest elongation east of ~22 degrees.



See highlight above.





Mars

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

Mars ,having graced our evening skies for many months (there was a beautiful grouping of Venus, Mars and a thin cresent Moon late in February) Mars is now finally sinking down into the Sun's glare.   It will lie close to, far brighter, Mercury around the 19th to 24th of the month.   With an angular size of just 4 arc seconds, no details will be seen on its, near fully illuminated, salmon pink surface.



See highlights above.





Venus

Venus
Venus showing some cloud structure

Venus,is shining brightly at magnitude ~-4 all month and rises higher in the western sky after sunset as the month progresses.  It starts the month in Aries, but climbs up into Taurus on April 7th, lying just to the east of the Pleaides cluster on the 13th.   A telescope will show its angular size increasing from 14 to 16 arc seconds whilst it illuminated phase shrinks from 78% to 68%.



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 mid evening April Sky

FebruarySky
The April Sky in the south - mid evening.

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
Gemini - click on image to enlarge

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

Gemini
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.

Gemini
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
Leo - click on image to enlarge

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.

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.

NGC2903
The 8.9th magnitude, type Sb, Galaxy NGC2903

The constellation Virgo

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.

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
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
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