Andromeda is an ancient constellation that represents one of the very few female figures in the night sky. It has many bright stars and is easily visible in the autumn night sky next to the asterism, the Square of Pegasus.
The most famous thing about this constellation is that it is home to the nearest spiral galaxy, the aptly named Andromeda Galaxy. Another claim to fame for this constellation is that it contains a star that has an extrasolar planet orbiting it. The name of the star is Upsilon Andromedae and this planet was one of the very first extrasolar planets to be discovered in the 1990’s.
The mythology behind the constellation is quite interesting and is a Greek myth. The mother of Andromeda, Queen Cassiopeia boasted that her beauty was greater than the sea nymphs. The nymphs were clearly outraged at hearing this remark and complained to the sea god Poseidon. Poseidon then ordered a monster called Cetus to ravage the country that Cassiopeia ruled. As a consequence of this, Andromeda was chained to a mountain as a sacrifice for the monster but fortunately Perseus the hero was on hand to destroy the monster with Medusa’s head.
The Andromeda Galaxy is a classic icon of astronomy that is instantly recognisable. The two elliptical companions increase the visual impact, the one that is closest to the Andromeda Galaxy is M32 and the other is M110.
Large telescopes are powerful enough to reveal some of the 400 globular clusters that are mostly situated in the outer halo. The brightest of these is Mayall II, the second brightest extragalactic globular cluster.
Click the image for a closer view by Johannes Schedler with enhanced visibility of nebulae.
|Image copyright A. Block/T. Puckett|
|Andromeda Galaxy (M31):|
This is a galaxy that is undoubtedly a classic image of astronomy. It is a spiral galaxy at a relatively close distance of 2.5 million light years.
The galaxy has two elliptical companion galaxies called M32 and M110. These are featureless and looking at them gives the impression that the Andromeda Galaxy is more detailed than it actually is. Rather surprisingly, M32 was classed as peculiar in the 1960's by astronomer Halton Arp, it is unexpectedly in the Arp Atlas of Peculiar Galaxies as Arp 168! Another thing the galaxy has two of are nuclei. Normally galaxies have one nucleus but this one has two. The second one was found with the Hubble Space Telescope in 2005.
Historically this galaxy is important, as in 1923 Edwin Hubble viewed the galaxy with a large telescope in the Mount Wilson observatory. He discovered that the so called ‘spiral nebulae’ were in fact like the Milky Way and were faraway collections of stars, gas and dust. Prior to this they were thought of as being distant solar systems.
This galaxy was the first one to be photographed, in 1887 by the British astronomer Isaac Roberts who later become well known for his astrophotography. Despite many details being revealed that wouldn't be visible visually, the astronomical community still clinged onto the incorrect perception of "spiral nebulae" as being clouds of dust and gas inside the Milky Way. Thankfully this outdated notion was discarded in the early 20th century when it was challenged by new discoveries being made with larger observatories.
The 'M' stands for Messier who was a French comet hunter. Charles Messier, while searching for comets, he often encountered fuzzy blobs that didn't move and stayed in a fixed place. In 1759, he started listing these objects in order to prevent them being confused as new comets. By 1781, his list had grown to 103 objects and was published. Many of the objects looked like indistinct fuzzy blobs through the small telescopes but when they were viewed with large observatories in the 19th century, their true nature became apparent. Currently there are 110 objects in the Messier catalogue but some consider there to be 109 and they refer to M110 by its NGC designation, NGC 205.
The Messier catalogue consists mainly of star clusters and galaxies and is usually observed by beginners as many Messier objects are bright and easy to locate using a technique called starhopping although this method might become obsolete due to the prevalence of computerised go to scopes.
Advanced observers like to challenge themselves by trying to observe all 110 Messier objects in a single night and many factors have to be considered when trying to achieve this feat successfully. For example the latitude of the observing site has to be southernly enough to be able to glimpse the most southern Messier objects. This challenge is aptly known as the 'Messier Marathon' and some astronomy clubs dedicate nights to this pursuit and award astronomers who manage to observe all of them in a single night.
|Andromeda Star Cloud (NGC 206):|
|This is a large cluster of very luminous and hot stars in the Andromeda Galaxy. It lies in a part that contains a lot of gas and dust. It is at the relatively young age of 20 million years. A counterpart in the Milky Way is the Sagittarius Star Cloud (M24).|
This is an ancient star cluster that is below the star Gamma Andromedae. It is approximately 1.5 billion years old and is much older than the Andromeda Star Cloud. Altogether it contains about 100 stars and it was discovered in 1654. Back then it would have been easily visible as a patch of light in the small telescopes available.
This is an exquisite edge on spiral galaxy that is very popular with skywatchers. The central disk has a copious amount of gas and dust. The dust absorbs blue light, so the overall colour is inclined to reddishness. The outer parts of the dust lane are thronged with numerous star forming regions and star clusters. As with many other galaxies, it has a part that is invisible in the optical wavelength. Scientific observations have revealed an extensive X-ray halo surrounding the galaxy. NGC 891 is part of a group of galaxies with the brightest member being NGC 1023 in Perseus.
|Blue Snowball Nebula (NGC 7662):|
As the name suggests, this planetary nebula has a blue colour. It is quite bright and its blue colour comes from the oxygen gas inside it being excited by ultraviolet radiation being emitted by the central star. The popular name originated in the 1960's.
|Within close proximity to the Blue Snowball Nebula lies this enchanting tightly wound barred spiral. The two spiral arms are quite indistinct and are very close to the central bar. This galaxy can be seen through small telescopes but might give the appearance of an elongated irregular galaxy. The visual appearance is reminiscent of NGC 4236 in Draco.|
|A highly dispersed open cluster, NGC 7686 is very easy to find as it is bright. The view through small telescopes is more desirable as the arrangement of approximately 30 stars is quite loose. Quite striking is a number of bright yellow stars embedded in the cluster along with a wondrous surrounding starfield.|
|Mirach's Ghost (NGC 404):|
In this cynical age, most people who claim to have seen a ghost are usually greeted with scepticism but the same cannot be said for astronomers who have been "haunted" by the spectre that resides near the star Mirach. This 'spectre' is a lenticular galaxy and is very difficult to see in a telescope because of its proximity to the star. It is magnitude 11, which means that it is faint; this also contributes to its elusiveness. It is generally featureless but it does have a bright nucleus and a subtle dust lane. The distance of NGC 404 is 11 million light years meaning that the absolute size is rather small.
Considering that the galaxy is akin to a ghost haunting the star Mirach, it is absurdly fitting that there actually is an interstellar ghost associated with the galaxy! The 'ghost' is a ring of hot new stars that can only be seen in ultraviolet, it was discovered by the GALEX space telescope in 2008. How is it possible for an ancient galaxy to have an unexpected young stellar generation?
It is currently believed that the ring was a byproduct of a collision with a nearby galaxy 900 million years ago. As a consequence of this, large swathes of molecular hydrogen were released and coalesced into a massive ring around NGC 404. This fueled the creation of hot young stars that can only be detected in the ultraviolet wavelength. Radio telescopes have shown that the molecular hydrogen ring perfectly lines up with the ultraviolet stellar ring.
|A fairly large spiral galaxy that has a soft texture to it. The spiral arms are very open and are dotted with red emission nebulae. A nice field of stars lies in the vicinity of the main structure. Unfortunately these stars make it a challenge to see the galaxy clearly as it is also fairly faint. It can be found near the variable star UY Andromedae close to the border with Perseus.|
NGC 70 is a very distant spiral galaxy that is incredibly faint at a magnitude of 14 and is part of a group of galaxies that are 300 million light years away. The group surrounding NGC 70 consists of two ellipticals, NGC 68 and NGC 71 as well as a barred spiral called NGC 72. Another name for NGC 70 is Arp 113.
|Fath and Abell 262:|
This strange sounding name is the identification for a group of galaxies that are part of the larger cluster Abell 262. This moderately bright galaxy cluster contains 40 members that can be seen in the largest scopes and has a total of 100 galaxies. Abell 262 can be found in the general vicinity of the open cluster NGC 752 and is near the border with Triangulum.
Images taken with highly sensitive CCD cameras reveal multitudinous chains of distant galaxies, almost indistinguishable from the sprinkling of foreground Milky Way stars, what betrays their presence is the highly redshifted golden light travelling through an unimaginable void. Most of these galaxies belong to a background supercluster that happens to share the line of sight with
|An enchanting sight in the skies of autumn, the Blue Snowball Nebula looks green in photographs rather than blue. If you look carefully, a ghostly halo can be seen around the nebula.|
|Image copyright A. Block|
The dominant galaxy in the Fath is NGC 708 and lies at the centre at a huge distance of 260 million light years. The Fath group resides towards the middle of Abell 262. This group is the easiest part of Abell 262 to observe but a fairly sizeable scope is still essential to see it.
Below NGC 708 is the edge on spindle of NGC 705 with the tightly wound spiral NGC 703 above it and the elliptical galaxy NGC 704 below. What looks like a star hugging the southern edge of the galaxy is in fact a circular galaxy designated as NGC 704B. Surprisingly the brightest member of Abell 262 lies just slightly below the Fath quartet, the spiral galaxy NGC 710 that shines at a lacklustre magnitude of 13.7 and is vaguely reminiscent of NGC 1288 in Eridanus.
Abell 262 is dominated by the giant elliptical galaxy NGC 708 although the majority of the member galaxies are spirals. The cluster is a strong source of X-rays that is centred on NGC 708. The galaxy cluster is part of the Pisces-Perseus super cluster. Other large galaxies include a pair of ellipticals to the right of the Fath, NGC 687 and UGC 1308.
The Abell Galaxy Cluster catalogue is a compilation that was an undertaking of the astronomer, George Abell. Many of the galaxy clusters were found by analysing photographic plates taken by the Palomar Observatory in the 1950's.
The criteria for inclusion in the catalogue was the richness of the galaxy cluster, the magnitude of the third brightest member and a minimum of 50 galaxies.
A pair of interacting spiral galaxies, Arp 273 is extremely faint and distant. The larger galaxy has an edge on companion and a gap of 13 000 light years separates the pair at a distance of 200 million light years making Arp 273 one of the most distant deep sky objects in Andromeda.
The larger galaxy, UGC 1810 has a magnitude of 12.5 and the smaller galaxy, UGC 1813 is one magnitude fainter. UGC 1813 has a very active nucleus and has more starburst activity than the larger galaxy possibly because of the greater influence of the gravity of UGC 1810. Also a very tenuous tidal bridge emanates from the part that faces the larger galaxy.
Arp 273 was discovered by the Russian astronomer, Boris Vorontsov-Velyaminov while working at the Sternberg Astronomical Institute in Moscow.
The Arp Atlas of Peculiar Galaxies is a compilation of different uncoventional galaxies and it was compiled by the astronomer, Halton Arp in the 1960's. The reason for the production of this atlas was to document different phonomenon found in galaxies in an attempt to explain the formation of regular galaxies. It was published in 1966 and was regarded as a valuable resource in understanding galactic evolution.
Altogether 338 galaxies were included and they were placed in distinct categories, which included galaxies with jets, interacting pairs and galaxies with 'heavy' spiral arms. In addition to the inclusion of faint distant obscure galaxies, there were also the inclusion of familiar popular galaxies such as the Whirlpool Galaxy in Canes Venatici and the Pinwheel Galaxy in Ursa Major.
Many of the Arp galaxies have the appearance of indistinct blobs when viewed through commercially available telescopes, some of the Arps look fuzzy even with 20 inch scopes. However there is an astonishing array of peculiar galaxies that look sizeable and reveal their bizarre structures.
Most of the Arp galaxies have more common designations that originate in the vastly more popular Messier and NGC catalogues. The implication of this is that many astronomers may have inadvertently observed or imaged Arp galaxies without the realisation that they are Arps. A contributing factor to this lack of realisation is that Arp galaxies are usually labelled with the NGC or Messier number on star atlases and only a certain portion of the Arp Atlas is plotted on star charts.
The Arp Atlas is commonly pursued by advanced amateur observers in need of a challenge and an increasing number of advanced amateurs are gaining access to ever increasing apertures. In addition to this is the advancement of the sensitivity of CCD cameras, which are able to reveal the faint wispy structures. Some astrophotographers have perfected the processing techniques of astrophotography to such a degree that it is possible for them to reveal unprecedented details never seen before.
The most well known Arp galaxies are due to them being imaged by the Hubble Space Telescope, these include Arp 188 in Draco and Arp 220 in Serpens. Arguably the most famous Arp is Arp 244, better known as the Antennae pair of interacting galaxies in Corvus. Another Arp that is popular with amateurs is Arp 214 in Ursa Major.
A decade later, Halton Arp in the 1970's began a southern equivalent of the catalogue in partnership with an astronomer called Barry Madore. This catalogue was abbreviated to 'AM' and was started in 1973 with the acquisition of suitable candidates onto photographic plates. After seven years of imaging the southern galaxies and an extensive analysis of the data, Arp and Madore realised that they had made some errors concerning the coordinates of the galaxies. They spent some more years rectifying the mistakes and the Arp Madore catalogue was eventually published in 1987.
The Arp Madore catalogue is relatively unknown in comparison to the Arp Atlas and the most well known galaxy is AM 0644-741 in Volans that was imaged by the Hubble Space Telescope in 2004. Some popular southern galaxies are also included in this catalogue, these include the Cartwheel Galaxy (AM 0035-335) in Sculptor, NGC 7424 (AM 0029-664) in Grus and NGC 2442 (AM 0736-692) in Volans.
Halton Arp is still currently active but is stigmatised from the astronomical community due to his controversial theories regarding redshifts of the peculiar galaxies and quasars. The stigma is of such extremity that astronomical research teams are barred from researching his unorthodox theories. Nevertheless his most well known work is deservedly the Arp Atlas and is an admirable legacy.
|Similar to vdB152 in Cepheus, this is a reflection nebula embedded at one end of a large dust tail. It is extremely faint and is also the last object in the van den Bergh nebula catalogue. Another similarity it shares with vdB152 is that there is a blue planetary nebula to the upper left of the reflection nebula called PK 110-12.1.|
An attractive barred spiral, NGC 90 is very faint and small but has a hypnotic spiral structure. The brightest parts of the two spiral arms wrap neatly around the bar but both have fainter extensions that stream in the direction of the spiral arms. The northern spiral arm has a larger extension that slightly tapers off at the end. These streamers are the result of NGC 90 interacting with the spiral galaxy NGC 93. Both of these galaxies are spectacularly faint at a magnitude of 14.4, therefore they require large telescopes and a copious amount of patience to be observed.
Both galaxies lie at an unfathomable distance of 220 million light years and both are also collectively known as Arp 65. Observations with the Spitzer infrared observatory have revealed the tidal streams of NGC 90 to be comprised almost entirely of a young stellar generation. This is evidence for tidally initiated star formation triggered by the interaction. These tidal streams can be revealed in long exposure astrophotography with large aperture telescopes as they are capable of collecting more light. Another thing that can only be seen via photographic means is an elusive galaxy above NGC 93. It appears to be a companion but this isn't possible as it lies four times more distant!
Following the northern stream of NGC 90 leads to a triangle of stars. The star that marks the base of the triangle has a distorted galaxy above it called NGC 83, which has extremely faint concentric shells. This might be the result of a past interaction with
Above NGC 83 is a faint gathering of dozens of galaxies, only a few of these can be vaguely glimpsed through the largest of telescopes. The brightest of these is another elliptical called NGC 85 with the elongated spiral galaxy IC 1546 to the left. It cannot be a coincidence that both lie next to each other, they seem to form a cosmic exclamation mark drifting through space! In addition to these galaxies, many more are situated above and below Arp 65, the whole region is a glorious yet largely unknown field that is drenched in an unfavourable shadow of obscurity!
|Classed as a peculiar galaxy, NGC 523 is an oddity that lies 250 million light years away. Due to its bizarre nature, it is also number 158 in the Arp Atlas of peculiar galaxies. The main structure is a bar connecting three knots together that look slightly like stars within the Milky Way. It is known that these knots actually belong to the galaxy as they share the identical redshift. Most likely this galaxy is the result of multiple colliding galaxies and if it was possible to view the appearance of the galaxy as it is right now, it might possibly be a barred spiral.|
Just a stone's throw away from the popular galaxy NGC 891, Abell 347 is a small but bright galaxy cluster with about 70 galaxies, the brightest being magnitude 13. This makes it a great target for advanced observers and any beginners exploring the dust lane of NGC 891 could nudge their scope a little southwards and attempt to view this galaxy cluster. One factor that simplifies locating the cluster is a bright yellow star near the cluster.
The cluster is centred on the 13th magnitude elliptical galaxy NGC 910. Surrounding it are 15th magnitude spirals that form a tight grouping around the central galaxy. Another fairly bright galaxy is the edge on spiral NGC 898, this is the brightest member that is closest to NGC 891 and the bright yellow star. Other notable members of Abell 347 include the wondrous galaxy pair of NGC 906 and NGC 914.
Some of the galaxies are interacting but the effects of this are impossible to detect visually as they are almost magnitude 16! Since the cluster is fairly small, large telescopes are required to see it. About half of the galaxies are brighter than magnitude 16 and these are concentrated together towards the centre, the other galaxies are on the outskirts, these would definitely require CCD astrophotography to be seen.
|Hickson 10 is a faint quartet of galaxies that are 200 million light years away. The brightest at magnitude 13 is NGC 536, a spiral galaxy with perpendicular streamers. These are likely to be the result of an ongoing interaction with spiral galaxy NGC 531, which lies below it and is almost a reflection of NGC 536 as it also has extensive streamers. Both these galaxies make a triplet with a tiny edge on galaxy, NGC 542 above them both with the fourth member of the group being to the right of them, a lenticular galaxy catalogued as NGC 529.|
|vdB158 is a surprising find in Andromeda and has gained an unexpected popularity with imagers due to its elusive contrasting nature. Try finding the blue planetary nebula!||Bizarre and offbeat, Arp 273 has been subjected to numerous scientific studies and analysis in various wavelengths.|
|Image copyright T. Davis||Image copyright D. Goldman|