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CURRENT MOON

Saturn

Saturn rises well after midnight and will be highest in the pre-dawn sky. Lying in the western part of Sagittarius, its diameter increases from 16.2 to 17 arc seconds during the month as it shines at magnitude +0.5. It will be high enough in the south-east before dawn to make out the beautiful ring system which, at over 26 degrees to the line of sight, are 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.

Jupiter

Jupiter, moving towards opposition on April 7th, lies in Virgo initially some 4 degrees above its brightest star, Spica. At the start of February it rises in the east at ~22:45 but by month's end by ~20:45. It will be due south at an elevation of 34 degrees at ~02:00 at the start and near 00:00 (UT) by the end of March. The size of Jupiter's disk increases slightly from 42 to 44 arc seconds as February progresses with its magnitude increasing very slightly from -2.3 to -2.5. 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 is easy to find as March begins lying in Pisces up and to the left of Venus some 13 degrees down to its lower right. As the month progresses, Mars continues to move eastwards ( moving into Aries on the 8th) whilst Venus falls back towards the western horizon. Its brightness falls slightly during the month from magnitude +1.3 to +1.5 whilst its angular diameter falls from 4.6 to 4.1 arc seconds. No details would be expected to be seen on its salmon-pink surface.
Venus
Venus starts the month dominating the western sky shining virtually at its brightest with a magnitude -4.8. It lies due south in mid-afternoon and can even by seen with the unaided eye. After dark in a very dark location it can even form shadows! On the 1st of February it has its highest elevation at sunset during the month at ~30 degrees. But then, as the month progresses, it falls back towards the Sun as it passes in front of it (inferior conjunction) on the 25th. Its angular size increases from 48 to 59 arc seconds during this time, but at the same time the phase reduces from 16% to 1% illuminated. These two effects compensate each other which is why the brightness only falls to ~-4.1. Very unusually, Venus is far enough north of the Sun that it will start rising before dawn on March 15th some 10 days before inferior conjunction. Thus it could be seen both at nightfall and at dawn for a few days! In visible light no details are seen on its brilliant white surface but cloud details can be seen or imaged in the ultra-violet. 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.

Mercury

Mercury passes through superior conjunction on March 7th and becomes visible around the 15th in bright twilight just above the western horizon. On the 19th, on its way up, it passes Venus, on its way down, some 9 degrees to its right. Then at magnitude -1.4, it brightness drops to -0.4 by the end of the month. With an angular size increasing to 7.3 arc seconds by month's end, no details would be expected to be seen on its disk.

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

Slide Presentation

The following presentation was given at our meeting on the 17th February, 2017 by Rob Slack

The constellation Taurus

Taurus is one of the most beautiful constellations and you can almost imagine the Bull charging down to the left towards Orion. His face is delineated by the "V" shaped cluster of stars called the Hyades, his eye is the red giant star Aldebaran and the tips of his horns are shown by the stars beta and zeta Tauri. Although alpha Tauri, Aldebaran, appears to lie amongst the stars of the Hyades cluster it is, in fact, less than half their distance lying 68 light years away from us. It is around 40 times the diameter of our Sun and 100 times as bright.



The Hyiades and Pleiades. Copyright: Alson Wong

More beautiful images by Alson Wong : Astrophotography by Alson Wong

To the upper right of Taurus lies the open cluster, M45, the Pleiades. Often called the Seven Sisters, it is one of the brightest and closest open clusters. The Pleiades cluster lies at a distance of 400 light years and contains over 3000 stars. The cluster, which is about 13 light years across, is moving towards the star Betelgeuse in Orion. Surrounding the brightest stars are seen blue reflection nebulae caused by reflected light from many small carbon grains. These relfection nebulae look blue as the dust grains scatter blue light more efficiently than red. The grains form part of a molecular cloud through which the cluster is currently passing. (Or, to be more precise, did 400 years ago!)


VLT image of the Crab Nebula

Close to the tip of the left hand horn lies the Crab Nebula, also called M1 as it is the first entry of Charles Messier's catalogue of nebulous objects. Lying 6500 light years from the Sun, it is the remains of a giant star that was seen to explode as a supernova in the year 1056. It may just be glimpsed with binoculars on a very clear dark night and a telescope will show it as a misty blur of light.


Lord Rosse's drawing of M1

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.

March 4th, following ~10pm : The Full Moon occults Gamma Tauri in the Hyades cluster


A Lunar Occultation in the Hyades Cluster.
Image: Stellarium/IM

During the late evening, the first quarter Moon will occult the star Gamma Tauri which forms the peak of the triangular shaped Hyades Cluster. Due to parallax, the timings will vary somewhat across the UK. After the Moon has set here, but visible across much of the USA, The Moon will occult Aldebaran. From a thin strip from Hertford in the East to Vancouver in the West, a grazing occultation would be seen with Aldebaran disappearing and reappearing many times as its light passes though the valleys lying along the Moon's limb.

10th March - all evening: The Moon, two days before full, closes on Regulus in Leo

The Moon closes on Regulus
Image: Stellarium/IM
If clear on the evening of the 10th and looking first to the east, one will see the Moon, two days before full, passing just below Regulus in Leo.
March 15th - before dawn: The Moon lies close to Jupiter and Spica

The Moon close to Jupiter and Spica in Virgo
Image: Stellarium/IM
If clear before dawn on the 15th and looking southwest, one will see Jupiter lying between the Moon to its upper left and Spica, Alpha Virginis, down to its lower left.
The constellation Orion
Orion, perhaps the most beautiful of constellations, will be seen in the south at around 11 - 12 pm during January. Orion is the hunter holding up a club and shield against the charge of Taurus, the Bull up and to his right. Alpha Orionis, or Betelgeuse, is a read supergiant star varying in size between three and four hundred times that of our Sun. The result is that its brightness varies somewhat. Beta Orionis, or Rigel, is a blue supergiant which, at around 1000 light years distance is about twice as far away as Betelgeuse. It has a 7th magnitude companion. The three stars of Orion's belt lie at a distance of around 1500 light years. Just below the lower left hand star lies a strip of nebulosity against which can be seen a pillar of dust in the shape of the chess-board knight. It is thus called the Horsehead Nebula. It shows up very well photographically but is exceedingly difficult to see visually - even with relativly large telescope.
The Orion Nebula

The Horsehead Nebula: Anglo Australian Observatory
Beneath the central star of the belt lies Orion's sword containing one of the most beautiful sights in the heavens - The Orion Nebula. It is a region of star formation and the reddish colour seen in photographs comes from Hydrogen excited by ultraviolet emitted from the very hot young stars that make up the Trapesium which is at its heart. The nebula, cradling the trapesium stars, is a beautiful sight in binoculars or, better still, a telescope. To the eye it appears greenish, not red, as the eye is much more sensitive to the green light emitted by ionized oxygen than the reddish glow from the hydrogen atoms.

The Orion Nebula: David Malin
March 20th - before dawn: Saturn near the third quarter Moon

Saturn near the third quarter Moon
Image: Stellarium/IM
Before dawn on the 20th and looking South, Saturn will be seen over to the right of the third quarter Moon.
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