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« March 2017


The Night Sky April 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.


New

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.

April 2017: A link to a 50 minute video 'The Art of Astrophotography'.

                    A survey of lunar and star charts, books and software.

                    Problems with Registax when using raw video files.





Image of the Month

UGC1259

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

This is a difficult galaxy (which lies at a distance of ~400 million light years) to identify as it has dark dust lanes like a spiral galaxy but a large diffuse bulge of stars like a lenticular galaxy.   Surprisingly, its outer parts are rotating at about 480 km/sec - almost twice as fast as in our galaxy and is the fastest rotation rate yet measured.   The mass needed to hold this galaxy together is several times the mass of our Milky Way Galaxy indicating a sunstantial amount of dark matter.


Highlights of the Month



April - a great month to view Jupiter.

Jupiter
Jupiter imaged by Damian Peach

This is a great month to observe Jupiter which comes into opposition on April 7th.   It is moving down the ecliptic and, at the start of April, lies in Virgo some 6 degrees above Spica (Alpha Virginis).   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.





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. The times are in UT.

1st   22.01         20th 22:38

3rd   23:39         23rd 20:07

6th   21:08         25th 21:45

8th   22:46         27th 23:23

11th 20:15         30th 20:53

13th 21:53        

18th 21:00


1st to 7th April - early evening after dusk: Mercury at its highest in the sky

Mercury
Mercury at its highest in the evening sky..
Image: Stellarium/IM

If clear on the evenings of the first week of April, Mercury will be seen above the western horizon after sunset.   Then it will have an elevation of some 18 degrees - so an excellent week to observe a somewhat elusive planet.



April 6/7th - all night : The waxing Moon closes on Regulus in Leo

Moon
The Moon closes in on Regulus in Leo.
Image: Stellarium/IM

During the darkness hours of the night of the 6/7th of April, a waxing Moon closes on Regulus and is within 2 degrees as dawn approaches on the 8th.


10th April - all night: The Moon, one day before full, passes Jupiter in Virgo.

Moon and Jupiter
The Moon and Jupiter.
Image: Stellarium/IM

If clear on the evening of the 10th and looking first to the south-east, one will see the Moon, one day before full, passing just 2 degrees above Jupiter in Virgo.


22nd April - after midnight: The peak of the Lyrid Meteors.

Lyrids
The Lyrid Meteor Shower.
Image: Stellarium/IM

Without any moonlight to hinder our view and from a dark rural location one, if clear, would have a chance of observing the peak of the Lyrid meteor shower with up to 10 meteors visible each hour.   As one might expect, the shower's radient is close to Vega in Lyra.


25th April - 1 hour after sunset: Mars passes between the Hyades and Pleiades Clusters.

Mars
Mars between the Hyades and Pleiades..
Image: Stellarium/IM

Looking low in the west after sunset on the evening of the 25th, Mars will be seen to lie directly between the Hyades (to its left) and Pleiades clusters - if clear, a nice photographic opportunity.


April 28th - a daylight occultation of Aldebaran

Aldabaran
The Moon occults Aldabaran.
Image: Stellarium/IM

Before dusk on the evening of the 28th, Aldebaran is occulted by a very thin crescent Moon.   It will disappear behind the Moon's dark limb at 19:11 BST as seen from London and 19:07 BST as seen from Edinburgh and reappear at the bright limb at 20:07 BST as seen from London and 19:57 BST from Edinburgh.   As darkness falls, Aldebaran will be seen to lie just below the Moon.   [Note: the sky brightness in the chart has been reduced.]


March 6th and 19th: The Alpine Valley

Alpine Valley
Alpine Valley region

An interesting valley on the Moon: The Alpine Valley
These are two good nights to observe an interesting feature on the Moon if you have a small telescope.  Close to the limb is the Appenine mountain chain that marks the edge of Mare Imbrium.   Towards the upper end you should see the cleft across them called the Alpine valley.   It is about 7 miles wide and 79 miles long.   As shown in the image is a thin rill runs along its length which is quite a challenge to observe.  The dark crater Plato will also be visible nearby.   You may also see the shadow cast by the mountain Mons Piton lying not far away in Mare Imbrium.   This is a very interesting region of the Moon!

The Alpine Valley
The Alpine valley and the crater Plato



M16, the Eagle nebula, imaged with the Faulkes Telescope

M16
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
April 26th April 3rd April 11th April 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

Jupiter

Jupiter
A Cassini image of Jupiter . Nasa

Jupiter comes into opposition on April 7th, lying in Virgo initially some 6 degrees above its brightest star, Spica.   Visible all night, It will be due south at an elevation of 34 degrees at around midnight UT.   The size of Jupiter's disk decreases slightly from 44.2 to 43.6 arc seconds as February progresses with its magnitude reducing very slightly from -2.5 to -2.4.   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.


Saturn

Saturn
The planet Saturn. Cassini - Nasa

Saturn rises around midnight (UT)and will be highest in the pre-dawn sky.   Lying in the western part of Sagittarius, its diameter increases from 17 to 18 arc seconds during the month as it brightness increases slightly from magnitude +0.4 to +0.3.   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 just acquired a ZWO Atmospheric Dispersion Corrector which uses two contra-rotating prisms to combat the dispersion of the atmosphere at low elevations.]



See highlight above.


Mercury

Mercury.
Messenger image of Mercury Nasa

Mercury passed through superior conjunction on March 7th and, on April 1st, will lie ~14 degrees above the western horizon at nightfall when it is at its greatest elongation, some 19 degrees, from the Sun.   Then at magnitude -0.2, it brightness drops to magnitude +3 by the 18th of the month as it falls back towards the Sun.   Mercury passes through inferior conjunction on the 20th and will reappear in the predawn sky by the end of the month.   With an angular size of to 7.5 arc seconds on the 1st, increasing to 11 arc seconds on the 18th, no details would be expected to be seen on its disk.





Mars

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

Mars. As April begins Mars lies in Aries but moves into Taurus on the 12th of the month.   In early April, Mars has an elevation of ~20 degrees above the western horizon at sunset, but this reduces to ~11 degrees by month's end.   On the 16th, it lies 4 degrees below the Pleaides cluster and then passes between the Pleiades and Hyades clusters on the 25th when it lies some 9 degrees to the right of Aldebaran.   Its brightness falls slightly during the month from magnitude +1.5 to +1.6 whilst its angular diameter falls from 4.2 to 3.9 arc seconds.   No details would be expected to be seen on its salmon-pink surface.



See highlight above.







Venus

Venus
Venus showing some cloud structure

Venus rises in the east about an hour before sunrise on the first of the month and then climbs a little higher each morning as April progresses.   On April 1st, the disk, forming a slender crescent nearly one arc minute tall, is just 2% lit shining with a magnitude of -4.2.   By the end of the month, Venus has its maximum brightness of magnitude -4.7 with its angular size reduced to 39 arc seconds and its illuminated fraction increased to 26%.   It will then have an elevation of ~13 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.   February's 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 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