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Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

The Monthly Sky Guide October 2018

 

Late October is normally the part of the year that finds those of us in the UK and Europe reverting to standard time (CET/GMT).  This is normally greeted with groans by those outside the astronomical community, as it leads to it getting darker earlier - those of us of a more astronomcial inclination will feel somewhat different, as it increases the opportunity for observations at a reasonable hour of the evening.  In the UK, the clocks go back on Sunday 28th October this year.  Those in North America will have to wait until the early part of November for this changeover to take place.  Naturally, what happens in the Northern Hemisphere has the opposite effect in the Southern.  Those in many territories in Australia and Brazil will begin their Daylight Saving Time (Summer Time) in October (New Zealand and Chile having started their DSTs somewhat earlier).

 Wherever you find yourself in the world, there's plenty going on in the skies above us this month...

 

The Solar System

 

The Moon

 

The Moon starts October in Northern Orion, at Waning Gibbous phase - rising a little after 10.30pm BST in the evening on the 1st. The Moon reaches Last Quarter the following evening, while residing in Gemini.

 

The Moon reaches New as it joins the Sun in Virgo on the 9th, after which it becomes an evening target. On the evening of the 11th, there will be the opportunity to observe the slim Crescent Moon, sitting around 4 1/2 degrees to the NW of Jupiter, in Libra, just after sundown.  

 

The Moon, Mercury and Jupiter, sunset, October 11th.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


The Moon reaches First Quarter on the 16th, in Sagittarius. The next evening, the Moon can be found joining Mars in neighbouring Aquarius. 

 

The Moon becomes Full on the 24th, in the non-zodiacal constellation of Cetus. Naturally, this is not the ideal time of the month for deep sky observations and imaging. 

 

The Moon ends the month on the 31st at its second Last Quarter of October, while in Cancer. 

 

 

Mercury

 

Mercury begins the month in the evening sky, separated from the Sun by around 8 degrees, in Virgo. From a northern hemisphere perspective, this is not a great time to observe the -0.8 mag, 4.8 arc second planet, as it sits 2 degrees high (from latitude 51 degrees N) at sunset. Southern hemisphere observers fare considerably better with Mercury in the evenings at this time of year, as the part of the ecliptic it is in sets at a much steeper angle than it does for us northerners - increasing the planet's elevation from the horizon. 

 

As ever with Mercury, nothing stays static for long. The planet's path heads out from the Sun, increasing angular distance from our parent star throughout the month. By the 15th, Mercury sits 16 1/3 degrees from the Sun, though has faded somewhat to -0.3 mag, presenting a 5.1 arc second diameter disk, some 90% illuminated. It still stands very low at sunset, barely 2 3/4 degrees high (from latitude 51 degrees N) at sunset, so won’t be observable form northern climes. Southern hemisphere observers, however, will continue to do considerably better as far as Mercury is concerned.

 

By the end of the month, Mercury sits 22 1/2 degrees from the Sun, shining at a steady, if unspectacular, -0.2 mag. Presenting a 6 arc second diameter, 74% illuminated disk. At a vertical angle from the horizon of about 3 1/2 degrees at sunset (from latitude 51 degrees N), seeing Mercury will be a very tough prospect from northern temperate latitudes, though observers in the equatorial and southern parts of the world will fare much better. 

 

Mercury, sunset, October 31st.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Venus

 

At the start of the month, Venus is found on the Virgo/Libra, shining at a brilliant -4.5 mag. Presenting a large 46.8 arc second disk, 16.6% illuminated to a thin crescent, the planet now sets virtually in line with the Sun and stands just under a degree high in the west at sunset (from latitude 51 degrees N). Venus will be easy enough to locate in daylight, being separated from the Sun by about 31 degrees. For those of us in the temperate northern hemisphere, this will be our only opportunity to observe our neighbouring world at the present, though observers in the tropics or the Southern Hemisphere will fare much better, as Venus will appear much higher in the sky at sunset. 

 

By mid-month, Venus has increased its size to a large 57.2 arc seconds diameter. It now displays a slither-thin 4.8% illuminated crescent and shines at -4.3 mag. The planet has crossed back into Virgo, moving in a westerly direction within the ecliptic as it catches the Earth up on its faster interior orbit. It now sits 18 degrees from the Sun and is rapidly approaching inferior conjunction. 

 

Inferior conjunction - where Venus appears between the Earth and the Sun - occurs on the 27th October. The planet will slide 6 degrees to the south of the Sun in the sky. By this point in time, Venus will be a massive (relatively speaking) 1 arc minute (60 arc seconds) across and present a 0.6% illuminated crescent, shining at -4.0 mag. After this, Venus will begin to reappear as a morning object. 

 

Venus at Superior Conjunction, October 27th.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


Venus ends October as a 1.2% illuminated crescent, still 1 arc minute across and now displaying brightness of -4.1 mag. It will stand 2 1/2 degrees elevation in the east as the Sun rises (from latitude 51 degrees N). 

 

 

Mars

 

By the beginning of the month, Mars can be found in Capricornus at -1.3 mag, displaying a 15.7 arc second diameter disk. The planet now stands 16 degrees high at transit point (from 51 degrees N), which it will reach at just before 9pm BST. 

 

By mid-October, Mars has shrunk to 13.7 arc seconds diameter and concurrently, to -1.0 mag, as we on Earth continue to pull away from the Red Planet on our faster interior orbit. By this time, Mars will stand just under 18 1/2 degrees high at transit point (from 51 degrees N), which it will reach at 8.29pm BST. 

 

Mars close to Transit point, October 15th. Note distinct Gibbous phase.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


At the end of October, Mars has faded further to -0.6 mag. The planet now displays an 11.9 arc second angular diameter and will stand just under 22 degrees high at transit (from 51 degrees N), which it will reach a little before 7pm (GMT). 

 

 

Jupiter

 

We're coming up to Jupiter's annual superior conjunction next month, so the window for observation of the solar system's largest world is pretty slim. At the beginning of the month, it is possible to observe Jupiter for a maximum of 1 1/2 hours after sunset, but the planet will be very low in the sky for observation in the northern hemisphere.   As the month progresses, the situation only becomes worse. We will now have to wait until 2019 to see Jupiter at its best again. 

Jupiter, with GRS transit, from zero degrees longitude, early evening 1st October. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


Saturn

 

At the beginning of the month, Saturn is found in Sagittarius . At +0.5 magnitude the ringed planet isn't vibrantly bright, but is still easy to spot. Saturn is now 16.4 arc seconds diameter. It reaches transit point at 6.32pm (BST), when it will stand just under 16 degrees high in the south. It will set at just before 10.30pm (again, BST, from 51 degrees N). The window for evening observation of Saturn is now beginning to close - so make the most of it while you can. 

 

By mid-October, Saturn remains static in brightness at +0.5 mag, though continues to shrink as we pull further away from it in the solar system - it is now 16.1 arc seconds diameter. The planet now reaches transit point at 5.40pm and sets at 9.37pm (again, BST, from 51 degrees N). 

 

Saturn and major moons, 15th October.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


By the end of the month, nothing much has changed as far as Saturn is concerned. The planet has faded to +0.6 magnitude and is now 15.7 arc seconds diameter. It reaches transit point at 3.42pm (GMT), when it will stand just under 16 degrees high in the south. It will set at just past 7.39pm (again, GMT, from 51 degrees N) - though this is good three hours after the Sun. The window for evening observation of Saturn is definitely coming to a close, as the planet heads towards superior conjunction on January 2nd 2019 - so make the most of it while you can. 

 

 

Uranus and Neptune

 

When last month found Neptune at opposition, this month is the turn of Uranus to reach its closest point to Earth this year. Uranus reaches opposition on the 24th October, when it will be just over 2.8 billion km from us. At this point, light travel time from Uranus to us will be 2 hours, 37 minutes - which considering the speed light moves at (299792 km per second), makes the planet a long way away from us!  

 

Relative positions of Uranus and Neptune, October 2018.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


Uranus will present a +5.7 magnitude, 3.7 arc second diameter target during October. While the major outer planets brighten significantly at opposition, both the outer gas giants are so far away from us that they don't vary significantly at their closest point to us. Still, Uranus is an interesting, if somewhat challenging target to find. On opposition night, the waxing gibbous Moon can be found around nine degrees to the SW of Uranus, making the area of sky the planet lurks in easier to identify (though scattered moonlight may make observations of the fainter planet somewhat difficult). The next night, on the 25th, the Moon comes even closer to Uranus' position, being found around 6 1/2 degrees to the SE. 

 

Uranus can be seen with the naked eye, but only under the most ideal conditions and by those who are really experienced observers, with excellent vision. The rest of us will have to content ourselves with views of the planet through binoculars or better still, a telescope. Telescopically, Uranus presents a green-gray disk, tiny in size and reminiscent of some of the brightest planetary nebulae. It is possible to observe the brighter of the major Uranian satellites, Titania and Oberon, with a telescope of 8-10" aperture (though preferably more), at high magnification. The inner major satellites, Ariel and Umbriel, require much more aperture and good sky conditions to pick out. However, it is reasonably straightforward to image all four with a modest telescope. The additional 23 known moons of Uranus remain hidden from direct observation on Earth and needed the visit of Voyager 2 to the Uranian system in 1986 to be discovered. 

 

Neptune is just past opposition, which it reached in September. It is not appreciably fainter than it was then, at +7.8 magnitude, but has shrunk but a minuscule 0.1 of an arc second to 2.3 arc seconds diameter. Now is still a great time to catch Neptune in the evening skies, as it appears in Aquarius - rising in the early evening and setting at nearly 4am (GMT) at mid-month. Just like Uranus, Neptune really needs powerful binoculars - or better still, a telescope, to see much of it at all. The Gibbous Moon provides a guide to its location on the evening of the 21st, as it slides 3 degrees to the south of the planet - though glare caused by our natural satellite may make it difficult to pick out Neptune (this is often dictated by your local sky conditions).

 

 

Comets

 

Periodic comet 46/P Wirtanen will be observable during a reasonably close (possibly naked eye) approach to Earth in mid-December.  The BAA Comet section has details online of a Pro/Am observation campaign that readers are encouraged to get involved in. It’s being run by the University of Maryland and details can be accessed here: http://wirtanen.astro.umd.edu/46P/Meetings_telecons/DPS2016_Wirtanen_workshop.pdf n telescopes for a period in September as it dips down towards the Sun.  Unfortunately, during October, the comet will be faint and plunging southward in the sky making it extremely difficult to observe.  Past the comet’s superior conjunction, on October 28th, it will rapidly climb northward again, getting closer to Earth as it does so. And brightening all the while.  So October is a bit of a wash-out as this comet is concerned, but there’s definitely more to come from it.

 

Another periodic comet, 21P/Giacobini-Zinner, will be well-placed for observation in early October, but the Moon will be in the same part of the sky as the comet during the early part of the month and won’t help viewing especially.  The comet passes through Monoceros in the first week of the month, sitting next to Orion in the sky, this makes the part of the heavens it is found in incredibly easy to locate - though this are won’t rise to reasonable height until the very early morning.  The comet continues south as the month progresses, crossing over into Canis Major and drawing near to Sirius, Alpha Canis Majoris, between the 13th and the 18th of the month.  Beyond this point, Giacobini-Zinner will start becoming difficult for temperate northern hemisphere observers as the hours of true darkness the comet appears in become limited.  The comet is likely to be 7th-8th magnitude during this period, making it fairly easy for observers with reasonably-sized binoculars and telescopes.

 

 21P/Giacobini-Zinner path through October (comet position shown for 1st Oct). Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


Meteors

 

The Orionid Meteor shower will peak on the 21st/22nd October this year.  This shower peaks at around 10-20 meteors per hour visible under ideal conditions, with the radiant well above the horizon.  

 

Unfortunately, on the night of peak activity this year, a 92% Gibbous Moon will be lurking on the Pisces/Aquarius borders and won’t set until 4.30am from temperate northern hemisphere locations, so will spoil the party somewhat.  However, for those rising early, there will be a brief window between the Moon’s setting and the onset of astronomical dawn to give yourself the best chance to catch some meteors.  By this time of the morning the radiant will be approaching transit in the south, so will offer the best chance to catch the fiery death of some of the debris left over by the most famous comet of all, P1/Halley (a trait the Orionids share with the Eta Aquariid shower of May).  When you see an Orionid, you're witnessing the demise of a tiny piece of the most famous of short period comets, meeting its end in the Earth’s atmosphere.


 

Deep Sky Delights in Pegasus And Andromeda

 

Moving slightly Northward from last month’s Deep Sky highlights in Aquarius and Capricorn, we come to the constellation of Pegasus, which is home to some easy and not-so-easy to observe objects and the interlinked Andromeda, home of some of the best-know objects in the sky, including the major galaxy, M31.  Below is and overview chart of this rich and interesting region.

 

Pegasus and Andromeda. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Though lacking in major nebulae, Pegasus is a haven for galaxies - maybe not quite to the extent of the Virgo and Leo regions - but has many extra-galactic targets worth attention. 

 

The most famous feature of Pegasus is readily observable without a telescope - this is, of course, the famous Square of Pegasus. Consisting of the stars Alpheratz (Arabic for “the navel”), Scheat (”the leg”), Algenib (”the flank”), Markab (”the saddle”), the Square of Pegasus dominates this area of sky and can be used as a useful “jumping off” guide for starhopping. However, the Square of Pegasus is not solely “of Pegasus”, as Alpheratz is actually now officially a part of neighbouring Andromeda. This is a similar situation to Elnath (Beta Tauri) which is officially now part of Taurus, but has been shared as Gamma Aurigae with neighbouring Auriga. These constellations are rare as they are still shown on modern star charts as connected via their “shared” star. 

 

A third of the way along the line between the lower stars of the Square, Markab and Algenib, lies an object not visible to the naked eye at all. This is the notable (if unspectacular) Pegasus Dwarf Galaxy, This is an associated galaxy with the nearby M31, the Andromeda Spiral and as such a neighbour of our own Milky Way. It’s a rather faint object at +13.2 mag and spread out over a reasonable area of sky, so is only really detectable in long duration photos. Dwarf galaxies are often (though not always) older, more primitive than galaxies such as our own. However, whilst they are not brilliant in the conventional visual sense, dwarf galaxies such as the Pegasus Dwarf are havens for Dark Matter. The Pegasus Dwarf lies 3 million light years away from the Milky Way and is tidally interactive with M31. 

 

Much more easily-observed and better-known is an object on the other side of Pegasus: the great globular cluster, M15. Found 4 degrees north-east of the star Enif (Arabic for “nose”), or Epsilon Pegasi, M15 is a glorious object in any telescope or binoculars and at +6.2 mag can be seen as a naked eye object from a reasonable site. This globular was discovered by Maraldi in September 1746 and catalogued 18 years later by Messier in 1764. Located about 33600 light years away, M15 contains around 100,000 stars. As a well-known object, it has been studied exhaustively and found to contain the first extra-galactic planetary nebula discovered: Pease 1, first identified in 1928. In addition to Pease 1, M15 has a pair of co-orbiting neutron stars, 8 pulsars and two strong X-ray sources. It has been postulated that one of these sources is in fact a Black Hole, to which has been attributed M15’s relatively recent core collapse. Globular clusters are both beautiful and intriguing objects and M15 is almost certain to contain more as-yet-undiscovered features. 

 

M15, pictured by the Hubble Space Telescope (showing Pease 1, upper left centre). Image Credit: NASA/ESA, Public Domain.

 

Back inside the Square of Pegasus lies the lovely NGC7814 - the “Little Sombrero” (so called because it resembles the Sombrero Galaxy, M104, in Virgo). NGC7814 is a Spiral, presented edge-on to our line of sight. This reveals a dark dust lane bisecting a bright core. At +10.6 mag this galaxy isn’t overly bright, but due to its compact nature, is still well-seen in small telescopes. NGC7814 is easily found due to its proximity to Algenib. 

 

NGC7814.  Image Credit: Hunter Wilson, Creative Commons.

 

Another galaxy near to a member of The Square is NGC7479, which lies just under 3 degrees south of Markab. This is one of the most photogenic Barred Spirals in the sky, lying almost face on to us. It was discovered in 1784 by William Herschel and is just slightly fainter than 7814 at +10.9 mag. NGC7479 is a very active galaxy - a so-called Seifert Type, in which enormous amounts of star formation are taking place. The serpentine structure of NGC7479 is beautifully depicted in long-duration photos - it almost seems to be slithering like a Sidewinder through space! 

 

NGC7479, pictured by the Hubble Space Telescope. Image Credit: NASA/ESA, Public Domain.

 

Further north are a fascinating collection of galaxies: the NGC7331 group and Stephan’s Quintet. These two groups of galaxies are separated by just half a degree of sky and can be found north of Matar (Eta Pegasi). Of the two groups, the NGC7331 group are the more conspicuous and their principle member was discovered first - by William Herschel - in 1784. This principle galaxy, NGC7331, was thought to be a very similar size, mass and taxonomy to our own Milky Way: a tightly-barred spiral. However, most up-to-date surveys of the Milky Way suggest that it may only have two massive spiral arms, whereas NGC7331 has more (NGC6744 in Pavo is now seen to be the nearest Milky Way analogue). Behind NGC7331 lie NGCs 7340, 7336, 7335, 7327 and 7338 - some of which can be seen with averted vision in reasonable-size telescopes. NGC7331 at +9.5 mag is by far and away the most prominent of the group and can be seen in smaller scopes. The whole group is a great target for astrophotography as regular contributor Mark Blundell’s picture below clearly shows. 

 

NGC7331 and Stephan's Quintet.  Image Credit: Mark Blundell.

 

The second of these two galaxy groups is the famous Stephan’s Quintet. Discovered in 1877 at Marseilles Observatory by Eduoard Stephan, the Quintet consists of NGCs 7317, 7318, 7318A, 7318B, 7319 and 7320 (this is technically a Sextet as 7318A and B are separate galaxial cores). Stephan’s Quintet occupies a tiny area of 3.5‘ x 3.5’ of sky and is an area of both enormous destruction, as the component galaxies literally rip each other apart and massive areas of creation where the resulting gas-rich loops of material released by these dynamics leads to starbirth. 

 

The interior of Stephan's Quintet, pictured by the Hubble Space Telescope. Image Credit: NASA/ESA, Public Domain.

 

Of the components of the Quintet, NGC7320 appears to be an unrelated foreground object - much closer to us at 39 million light years distance as opposed to the 210-350 million light years of the other members. It is obvious that NGC7331 is the biggest and brightest of any member of either group and can be observed by those with telescopes of modest aperture. But Stephan’s Quintet is still observable with instruments of 10-inch apertures and above, with members ranging from +12.5 to +13.6 mag. However, again, it is astrophotography that really shows the Quintet in all its destructive and creative splendour.

 

Crossing the border into Andromeda and turn our attention to the less well-known, but prominent and easily-found galaxy in the constellation: the wonderful NGC891. 11 1/2 degrees to the SE of M76 and discovered by Sir William Herschel in 1784, NGC891 is a spiral galaxy, potentially much like our own, presented absolutely edge-on to our perspective. At +9.89 mag, it is not especially bright, but it is well-condensed. Its axis is bisected by a dark dust lane, splitting the object in two. In telescopes of moderate aperture, NGC9891 appears like a shard - or rather two parallel shards of light, with a very small bulge of the galaxy’s core in the centre. It is a lovely object - maybe not having the glamour of its neighbour M31 (NGC891 is 30 million light years away from us), but a very rewarding galaxy to observe or photograph. 

 

3-degrees to the west of NGC891 can be found Gamma Andromedae, or Almach - an easy pointer to the galaxy, but an equally interesting object in its own right. Almach is one of the sky’s best double stars: a pair of orange-yellow and striking greeny-blue stars of +2.17 and +4.75 mag respectively. The principle element of the system is a K3 giant star, nearing the end of its life. However, the fainter secondary green-blue star is itself a double - albeit a very difficult one. It will take telescopes in the 30-inch + class to split this second double. However, in coming years, this secondary element will become steadily easier to split with smaller instruments as the elements drift apart around their mutual gravitational centre - although it will be the mid-2020s before they are resolvable with 8-inch class telescopes. The main elements of Gamma Andromedae are gloriously split in most small telescopes. Even for those with the smallest of telescopes should have a go at splitting this star. 

 

Andromeda is, of course, home to the most prominent galaxy in the sky - M31 and its attendant satellite galaxies M32 and M110. As a major member of our Local Group of Galaxies, the M31 system is the largest gravitational influence on our own Milky Way and in under 4 Billion years it is likely the two Spirals will collide and eventually form a large Spheroid elliptical Galaxy. Approaching the Milky Way at around 300km per second, M31 is already a huge angular size - the boundaries of which stretch over 6 times the width of the Full Moon in the sky. At +3.4 mag, M31 was probably one of the first Deep Sky objects - certainly the first galaxy - to be noticed by humanity. First recorded by the great Persian Astronomer Abdul al-Rahman al-Su in his 962CE text “Book of Fixed Stars”, al-Rahman described M31 as the “Little Cloud” - and while his is the first record of the object, it was doubtlessly noticed sooner, being the most prominent deep sky object alongside the Pleiades and Hyades in Taurus and M42 in Orion. 

 

M31by Mark Blundell.  Image used by kind permission.

 

Simon Marius first turned a telescope to M31 in 1612, though made no claim to its discovery - he may have been aware of it from earlier star charts - a Dutch example dating from 1500 shows the object. Throughout the 17th and 18th Centuries, the Galaxy was “re-discovered” independently by astronomers. While there was clearly communication between astronomers of the era regarding M31, many, including Edmund Halley, erroneously credited the discovery of the object to different people. Charles Messier credited its discovery to Marius, when forming his famous Messier list in 1764. Theories abounded as to the true nature of M31: a nascent Solar System forming, a cloud of glowing gas forming stars, a dying, decomposing star. Spectroscopy hinted at the true nature of M31. William Huggins , the early adopter of telescopic spectroscopy found that unlike many other nebulae, M31 exhibits a broad, continuous spectral response, rather than the definitive lined spectra of a gaseous nebula. Something that clearly set M31 apart from the likes of M42. In 1887, the first of many, many photographs of the galaxy was taken by Isaac Roberts from Crowborough in Sussex (just a short journey from the location of Telescope House in Edenbridge). Robert’s beautiful picture clearly shows dust lanes in the outer spiral arms and the satellite galaxies of M32 and M110, much as Mark Blundell’s more modern portrait does above. 

 

M31by Isaac Roberts, taken in 1887.  Public Domain.

 

Roberts subscribed to the theory that M31 was a Solar System in the early stages of formation. However, this theory was put to bed by mounting evidence of Novae observed and photographed within the reaches of M31. Heber Curtis discovered his first Nova in M31 in 1917 and went on to find a further 11. These were observed to be a mean of 10 magnitudes fainter than those observed within our own galaxy, leading to Curtis to suspect that M31 was considerably further away than first thought. Curtis was amongst those Astronomers that put forward the theory that objects of this type were “Island Universes”. This was famously debated in a meeting between Curtis and Harlow Shapely in 1920 - Curtis was for, Shapely against. 

 

The matter was settled in 1925 by Edwin Hubble, who discovered the first Cepheid Variable in M31. Comparisons with these variables and the Cepheids in our Galaxy proved that M31 was a separate conglomeration of stars, distinct from the Milky Way. Although underestimating the distance of M31 by a factor of two, Hubble proved that the Universe was a much larger and more mysterious place. 

 

Walter Baade, using the 200-inch Palomar Reflector discovered two separate types of Cepheids Variables in the population of M31, which had the effect of doubling Hubble’s pervious distance estimate in 1943. Current distance estimates are around the 2.5 million light years mark. M31 was also discovered to be heavily blueshifted in its spectral lines, proving via the Doppler effect that unlike the vast majority of galaxies in the sky, it is actually advancing towards us (or more accurately, both galaxies are attracting one another). 

 

M31 can be observed with (or without) all manner of optical equipment. It is probably best seen in large Binoculars (70mm objective size +) from a reasonably dark location. Rich eld, short focal ratio telescopes like Dobsonians, and shorter Refractors show it well too, but due to its large angular size, powers must be kept low to see the Andromeda Galaxy in all its glory. Both satellite galaxies, M32 and M110 are easy to spot too (M32 the easier of the two). In larger instruments, with suitable filtration, it is possible to observe nebulous regions in M31 - similar features to the Orion Nebula in the Milky Way. This is a challenge, but a rewarding one! We’ll never see the true beauty of our own galaxy from the outside, so must content ourselves with the marvellous vista that M31 offers us. Some of M31’s globular clusters, including the remarkably large G1 are also visible though instruments of 10-inch aperture and above. 

 

However, it is in long duration photography that M31 really reveals its true extent and size. A 30 second unguided exposure with a wide field lens will easily show M31, though a small, high-quality refractor on an equatorial mount will be ideal in terms of framing the whole object on a standard DSLR chip. Multiple exposures, when stacked in a free program such as Deep Sky Stacker, will reveal the huge dust lanes and knotted, hydrogen rich areas of nebulosity. M31 is a prime beginner’s Deep Sky photographic target, but it is such a rewarding photographic object that Astrophotographers feel compelled to return to it time and time again. That it is well-placed for those of us in the northern hemisphere during the winter months is indeed fortuitous. All though observable through much of the year, now is the time to take full advantage of this fabulous Deep Sky wonder. 

 

To the western side of Andromeda, 2.5-degrees to the W of Iota Andromedae is the lovely NGC7662 - otherwise known as the Blue Snowball Nebula. This Planetary Nebula is a great object - albeit compact, at 0.5 minutes of arc - and is well seen in telescopes of most apertures. A 6-8-inch class telescope will show it clearly as a blue-green ball of light. However in larger telescopes, the subtleties of NGC7662 really become noticeable - it’s internal rings and slight elongated internal lobes can be distinct. The Blue Snowball can exhibit “blinking” just like the famous Blinking Planetary and Saturn Nebula. The Blue Snowball’s central white dwarf star shows distinct variability - peaking at +12 mag, but sometimes dimming down to below +16 mag. Current distance estimates put it at 5,600 light years distance from us and 0.8 light years in diameter. 

 

NGC 7662, The Blue Snowball Nebula.  Image by Tom Wildoner, Creative Commons.  Image composed of 32 x 15 second images at ISO 3200 with additional dark and bias frames using a Meade LX90 12” telescope, Antares Focal Reducer, and Canon 6D camera.


Drifting back east, beyond M31 and its companions, we come to two unusual objects. Mirach and Mirach’s Ghost are formed by Beta Andromedae and a condensed elliptical galaxy, NGC404. Line of sight from our perspective on Earth place these two completely unrelated objects in a very close pairing - they are separated by just under 7 arc minutes, making this galaxy easy to locate, but not necessarily so easy to see. Mirach has a tendency to overpower its neighbour, due the their differences in brightness. In clear, calm conditions NGC404 can be spotted in large binoculars, though telescopic observation can be a little trickier. Higher magnification can help under some conditions, though aperture will help as well. Photography of NGC404 is a challenge as well, but a worthwhile one. Mirach and Mirach’s Ghost are one of those interesting “Odd Couples” of the night sky, that perspective and chance throws our way. It would be a pity to let the perceived difficulty of observation stand in the way of taking a look. 

 

Mirach and Mirach's Ghost.   Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Another of Andromeda’s obscurer residents is the open cluster NGC752. Consisting of over 70 stars of around the 9th magnitude, NGC752’s cumulative magnitude stands at +5.7. Best seen in giant binoculars, this cluster has some particularly elderly residents for a star cluster: its A2-class stars indicate an age of over a billion years. The cluster is full of star chains and occupies an area of over 75 minutes of arc in the sky. It lies over 1500 light years from Earth. 


 

Text: Kerin Smith