Explore Astronomy

Astronomy Picture of the Day
« April 2019


The Night Sky May 2019


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(ish)

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.   It now includes well over 50 illustrated articles.




Image of the Month

M87

M87, Jets and 'Black Hole'
Image: NASA, JPL-Caltech and Event Horizon Telescope Collaboration.

M87, also known as Virgo A, lies at a distance of 55 million light years at the heart of the Virgo Cluster of Galaxies.   It is one of the most massive galaxies in the Universe whose total mass may be ~200 times that of our Milky Way galaxy.   This image of the Virgo Cluster was taken in the infrared by the Spitzer Space Telescope with an expanded view showing the jets enimating from a region surrounding a super-massive black hole at its heart.   The brighter jet is coming towards us.   These jets are powered by material falling in towards the black hole giving rise to 'synchrotron' emission that was imaged by the Event Horizon Telescope at sub-mm radio wavelengths - so this is a false colour image.   The image shows the 'shadow' of the black hole which is about two and a half times the diameter of the black hole itself.

  'The features of the image support the interpretation that we are seeing emission from near the event horizon (the edge of the black hole) which is gravitationally lensed into a crescent shape.   The central flux depression is the result of photons captured by the black hole: the black hole shadow.'

  A major part of the software used to produce the image was initially developed at our observatory to produce images from the MERLIN array which has a similar 'sparce' array of telescopes as does the Event Horizon telescope.



Highlights of the Month



May 7th - after sunset: Mars lies above a thin crescent Moon.

Mars
Mars above a thin crescent Moon
Image: Stellarium/IM

Given a low horizon looking towards the west after sunset one should, if clear, be able to spot Mars lying halfway between Betelgeuse and Capella above a very thin crescent Moon.

May 12th - evening: The Moon in Leo

Moon
The Moon in Leo
Image: Stellarium/IM

Looking southwest in the evening a first quarter Moon will be seen lying close to Regulus in Leo.

May 19th - early evening: Mars above M35 in Gemini.

Mars
Mars above M35 in Gemini.
Image: Stellarium/IM

Looking west in early evening if clear, and using binoculars or a small telescope one could see Mars lying just above the open cluster, M35, in Gemini.   Perhaps a last chance to see Mars at the very end of its apparition.

May20th - midnight: Jupiter and the Moon.

Jupiter
Jupiter and the Moon
Image: Stellarium/IM

During the night of the 20 May, Jupiter will lie over to the right of the waning gibbous Moon.


May 23rd - early morning: Saturn and the Moon.

Saturn
.
Image: Stellarium/IM

In the early Morning of the 23rd of May, Saturn will lie up to the right of the waning gibbous Moon.


May 28th - around midnight: spot asteroid 1, Ceres.

Ceres
Asteroid 1, Ceres.
Image: Stellarium/IM

On the 28th May, Ceres is at its closest approach to Earth lying over to the right of Jupiter.   It will have a magnitude of 7 so binoculars should enable you to spot it and the chart will help you find it.   A planetarium program such as Stellarium will show you its position in the days before and after its closest approach.   Ceres is the largest of the minor planets and is now classified as a 'Dwarf Planet'.


Ceres
Ceres Chart, Stellarium


May 11th and 25th, evening: The Hyginus Rille

20thJuly
Hyginus Rille location: IM.

These evenings, should it be clear, are a superb time to view the Hyginus Rill as it will lie close (very close on the 25th) 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

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 third quarter
May 4th May 12th May 18th May 26th

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 9,550 pixels.  The resolution of ~0.4 arc seconds 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 8 day old Moon

Lunar Image
The 8 day old Moon imaged by Ian Morison.

This image was taken by the author on a night in March 2018 when the Moon was at an elevation of ~52 degrees and the seeing was excellent.   This enabled the resolution of the image to be largely determined by the resolution of the 200 mm aperture telescope and the 3.75 micron pixel size of the Point Grey Chameleon 1.3 megapixel video camera.   The use of a near infrared filter allowed imaging to take place before it was dark and also reduced the effects of atmospheric turbulence.   The 'Drizzle' technique developed by the Hubble Space Telescope Institute (HSTI) was used to reduce the effective size of the camera's pixels to allow the image to be well sampled.   Around 100 gigabytes of data, acquired over a 2 hour period, was processed to produce images of 54 overlapping areas of the Moon which were then combined to give the full lunar disk in the free 'stitching' program Microsoft ICE.   A further HSTI development called 'deconvolution sharpening' was then applied to the image.   The Moon's disk is ~6,900 pixels in height and has a resolution of 0.6 to 0.7 arc seconds.   Interestingly, as seen in the inset image, the rille lying along the centre of the Alpine Valley is just discernable and this is only ~0.5 km wide!   [Due to size limitations the large image is 2/3 full size.]









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 starts the month shining at magnitude -2.5 which increases to to -2.6 as the month progresses.   At the same time, its angular size increases from 43 to 46 arc seconds.   As May begins it rises by midnight UT so will be due south around 3 am UT whilst at month's end it rises at ~9:30 pm UT so due south at ~01:30 UT.   Sadly it is heading towards the southernmost part of the ecliptic and currently lies in the southern part of Ophiuchus just above Scorpius so, as it crosses the meridian, it will only have an elevation of ~14 degrees.   It lies just above the centre of the Milky Way.   Atmospheric dispersion will thus take its toll and an atmospheric dispersion corrector would greatly help to improve our views of the giant planet.



Saturn

Saturn
The planet Saturn. Cassini - Nasa

Saturn, shining with a magnitude increasing from +0.5 to +0.3 during the month, rises around midnight during the month so crosses the meridian just before dawn.   Its disk is ~18 arc seconds across and its rings - which are still nicely tilted from the line of sight - spanning 40 arc seconds across.   Morning twilight is the best time to observe it but, sadly, now in Sagittarius and lying on the southern side of the milky way, it is at the lowest point of the ecliptic and will only reach an elevation of ~10 degrees.   As with Jupiter, an atmospheric dispersion corrector will help improve our view.




Mercury

Mercury.
Messenger image of Mercury Nasa

Mercury passes through superior conjunction (behind the Sun) on May 21st and will only be visible, low in the west-northwest, on the last few days of the month.   One will need a very low horizon and binoculars could well be needed to reduce the Sun's background glare, but please do not use them until after the Sun has set.






Mars

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

Mars, though fading from +1.6 to +1.8 magnitudes during the month, is still visible in Taurus in the south western sky after sunset lying half way between Betelgeuse, in Orion, and Capella, in Auriga.   Mars sets some three hours after the Sun at the start of May (with an elevation as darkness falls of ~20 degrees) but less than two and a half hours by month's end.   Its angular size falls from 4.2 arc seconds to less than 4 arc seconds during the month so one will not be able to spot any details on its salmon-pink surface.




Venus

Venus
Venus showing some cloud structure

Venus has a magnitude of -3.8 in May with its angular size reducing from 11.5 to 10.8 arc seconds during the month as it moves away from the Earth.   However, at the same time, the percentage illuminated disk (its phase) increases from 88% to 92% - which is why the brightness remains constant at 3.8 magnitudes.   It rises about an hour before the Sun but its elevation is only ~4 degrees at sunrise so a very low horizon in the East is required and binoculars may well be needed to spot it through the Sun's glare - but please do not use them after the Sun has risen.

Radar Image of Venus
Radar image showing surface features











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
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

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

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.

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