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CURRENT MOON

Saturn

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.]

Jupiter

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.

Mars

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
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.

Mercury

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

Compiled by Ian Morison - Jodrell Bank Centre for Astrophysics
The Night Sky In and Around Swindon May 2017

Slide Presentation

The following presentation was given at our meeting on the 21 April, 2017 by Rob Slack

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 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 million light 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.



The galaxies M65 and M66

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.


The galaxies M95 and M96

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

Its name "The Crab Nebula" was given to it by the Third Earl of Rosse who observed it with the 72 inch reflector at Birr Castle in County Offaly in central Ireland. As shown in the drawing above, it appeared to him rather lile a spider crab. The 72 inch was the world's largest telelescope for many years. At the heart of the Crab Nebula is a neutron star, the result of the collapse of the original star's core. Although only around 20 km in diameter it weighs more than our Sun and is spinning 30 times a second. Its rotating magnetic field generate beams of light and radio waves which sweep across the sky. As a result, a radio telescope will pick up very regular pulses of radiation and the object is thus also known a Pulsar. Its pulses are monitored each day at Jodrell Bank with a 13m radio telescope.

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

May: Look for the Great Red Spot on Jupiter

Observe the Great Red Spot
Image: NASA
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
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.

The Giant Elliptical Galaxy M87
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.

M104 - The Sombrero Galaxy
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.
The constellation 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
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.


M97 - The Owl Planetary Nebula

Lord Rosse's 1848 drawing of the Owl Nebula
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. You might also try and find Amalthea, the fifth largest Jovian moon and the only other moon that can be seen in an amatuer telescope.