Solar System

(The Centaur)

Centaurus is a southernly constellation that represents a mythological creature called a centaur. In Greek myths, centaurs were creatures that had the upper half of a person and a lower half of a horse.

Centaurus is the ninth largest constellation and yields a multitude of deep sky objects and interesting stars. It is home to both the closest and the second closest stars. The second closest is Alpha Centauri, which is one of the 20 brightest stars. The closest is Proxima Centauri and is only four light years away. The Milky Way is very prevalent in Centaurus and sweeping star fields are very common.

This constellation might represent a specific mythological character, Chiron the centaur from Greek myths.

  Omega Centauri    
    Bursting with millions of stars, Omega Centauri is the most richly populated globular cluster in the entire sky. It is generally regarded as the greatest globular cluster.    
Image copyright D. Verschatse
    Omega Centauri (NGC 5139):

Glorious and spectacular are a few of the words that could be used to describe this undeniably magical globular cluster. It is so bright that in the 16th century, Johannes Bayer catalogued it as a star. The magnitude is number four and it is the largest cluster in the sky. It wasn't until 1677 when Edmond Halley turned his telescope to this 'star' and found it was a glorious globular cluster. Edmond Halley was also the discoverer of Halley's Comet.

Overflowing with stars, it contains a mind boggling 10 million stars and it is rumoured that this cluster might be the remains of a dwarf galaxy. This seems consistent with its immense age of 12 billion years, which is when early galaxies were being formed although don't confuse the age of the cluster with the number of years since light left it. The distance is 16 000 light years, so we see it as it was
16 000 years ago when humanity hadn't formed any major civilisations. To further add to the tantalizing mystery, the Hubble Space Telescope in 2008 found evidence of an intermediate black hole at the heart of this beast. Another globular with a black hole is Mayall II inside the Andromeda Galaxy.

Centaurus A (NGC 5128):

The view through a small telescope shows this galaxy appearing as an elliptical galaxy with what looks like an edge on galaxy perched in front of it. In reality this is an active nucleus that belongs to one of the nearest radio galaxies. At the heart of this nucleus lies a ravenous supermassive black hole.

Mentioned previously, radio galaxies are a type of galaxy that release radio waves. Centaurus A is one of the most laborous radio galaxies releasing 1000 times the radio energy of the Milky Way.

These radio waves are visible with radio telescopes in the form of jets that project from the nucleus in opposite directions. There are two of these jets that are almost one million light years long.

This unusual galaxy was formed under familiar circumstances, it was a merger between an elliptical galaxy and a spiral galaxy. Ellipticals are usually featureless but there are many tidal streamers of stars that punctuate the space between the brown centre and the pearl glow of the elliptical part. For obvious reasons, it is no surprise that Centaurus A is also known as Arp 153.

NGC 4945:
Caked in interstellar dust is what this edge on spiral galaxy is. Most of the galaxy is sprinkled with purplish star clouds and ghostly blue star clusters. This shows that the galaxy is active and it is also bright in infrared.
NGC 4945      
NGC 4945 is a highly energetic galaxy that is enveloped in numerous stages of star formation. The nucleus is thought to contain a black hole as well as emitting a copious amount of x-ray and infrared radiation.      
Image copyright W. Kloehr
Running Chicken Nebula (IC 2944) and IC 2948:

One of the many bird shaped nebulae in the heavens, the Running Chicken Nebula is near the star Lambda Centauri, which is near the apex of the nebula complex. The brightest part is in the southern quadrant and what contributes to the brightness is the iridescent charm of the white stars of IC 2948, an open cluster inside the nebula.

The brightest part is also obscured by a group of dark blobs known as Bok globules. These were discovered by Bart Bok and this nebula might be where they were first observed. They are sites of strenuous star formation and are found in other nebulae such as the Pacman Nebula in Cassiopeia.

In the vicinity of this large nebula, many interesting deep sky objects can be found such as smaller nebulae that belong to the RCW and Gum catalogues, the pearly glean of the open cluster NGC 3766 as well a faint obscure planetary nebula known as He2-72, which is exclusive to telescopic views and an OIII filter is preferable for observing it.

NGC 3766:

This naked eye cluster is magnitude 5 and is 5500 light years away, which is a very short distance. It is near the Running Chicken Nebula and contains many blue stars and shimmering red giants that add to its lustre.

NGC 3918:

A tiny planetary nebula that is easily visible in small telescopes due to its very bright magnitude of 8. What it lacks in size, it makes up in its intense aqua blue colourisation that is unmistakable.

It was discovered by John Herschel in 1834 who named it the Blue Planetary, it is quite strikingly similar to planet Neptune.

NGC 5286:
Lying near the planetary nebula NGC 5307, this moderately dense globular cluster is adjacent to the binary star, M Centauri. It contains thousands of yellow stars and its angular size is fairly small so it will appear more clearly in larger telescopes.
NGC 5367:
An attractive fluffy textured reflection nebula surrounding a 9th magnitude star embedded in the brown dust of the cometary globule, CG12. South of the main reflection nebula is a smaller nebula that surrounds a magnitude 10 double star. North of the main nebula is a fountain of dark nebulosity that contrasts nicely with both the opaqueness of the brown dust and the blue glow of the reflection nebulosity, this is Be 146. In the vicinity are some background galaxies, more would probably be visible if the cometary globule was non existent. The area is also characterized by the golden light of old yellow stars, which further increases the visual appeal of this fascinating region.
Cometary globule CG12 and reflection nebula NGC 5367        
Like a comet in the sky, NGC 5367 appears to have a blue nucleus and a brownish tail.        
Image copyright G. Rhemann and M. Jäger
NGC 5102:
A luminously blue lenticular galaxy that has undergone a recent episode of star formation in its nucleus. It also has a supershell that is ring shaped, which is unusual for this type of galaxy.
NGC 5617:
Easy to find, NGC 5617 is very close to Alpha Centauri. It is a striking blue coloured open cluster that consists of 80 stars. Nearby is the golden glow of the faint open cluster Pismis 19.
NGC 5253:
This remarkable and incredible galaxy is a starburst dwarf. What owes to its incredibility is that it contains at its centre, an immensely vociferous radio and infrared source. This source is a super star cluster and it was observed in 2000 with the Hubble Space Telescope. What it uncovered was that this super star cluster was a precursor to morphing into a giant globular cluster. In other words this was the first globular cluster to be observed while it was in the process of formation.
NGC 3699:

When you look at this planetary nebula, you might think it is a ghost of the galaxy Centaurus A. The unnerving resemblance is quite uncanny as it has a bi-polar structure with an absence of gas through the centre lending it the mysterious appearance.

Unlike Centaurus A, it is very tiny and extremely faint at a retina straining magnitude 14 brightness. Due to its bi-polar nature, it was thought of as being an emission nebula until 1978. Humourously, the bi-polar emission nebula NGC 6164-5 in Norma was originally thought of as being a planetary nebula.

NGC 5091, NGC 5090 and NGC 5082:
An obscure group of galaxies that are short of being considered as dazzlingly spectacular. All three of them lie at a distance of between 40 and 50 million light years away. The limelight is stolen from NGC 5082 by the interacting pair of
NGC 5091 and NGC 5090. What makes this pairing refreshingly different is that
NGC 5091 is an edge on spiral galaxy but NGC 5090 is a bright elliptical with a luminous core and thousands of globular clusters in its halo making it similar in appearance to M87 in Virgo. One factor in NGC 5082 receiving minimal attention is that it is a fairly featureless spiral galaxy with weak empty spiral arms that lack star formation due to being devoid of gas and dust.

One of many planetary nebulae in Centaurus belonging to obscure catalogues, Fg1 is a tiny but bright emerald green shell of glowing gas shining at a magnitude of 11. Elliptically shaped, two darkened jets similar to Herbig Haro objects protrude outwards from the central star in a polar symmetrical manner.

Scientific analysis has shown that the expansional velocity of the gas in the knots of the jets is due to the gas being excited by collisions. These knots could be ansae that were formed in the proto-planetary stage. Ansae are a type of structure found only in planetary nebulae, the most well known planetary nebula with ansae is the
Saturn Nebula in Aquarius.

This vibrant object was discovered almost a century ago in 1910 by Williamina Fleming, a year before her untimely death. It is also in the southern Henize planetary nebula catalogue. It requires large apertures to reveal the darkened jets and an OIII filter increases contrast against the star filled background.

RCW 49:

A very busy emission nebula, RCW 49 is a hive of frenzied activity. The source of the nebula's visibility is the gargantuan open cluster, Westerlund 2. It is very young at only 2 million years and is home to some of the Milky Way's largest stars.

Studies with the Spitzer Space Telescope have unveiled a series of proto-planetary disks encircling some of the fledgling stars. These are some of the most distant proto-planetary disks that have been discovered, the nebula is 20 000 light years away, quite considerable for a nebula.

RCW 86:

Throughout the past thousand years, there have been many historical records of a new star flickering into existence in a part of the sky. Most of these would have been a supernova explosion, the titanic conclusion to a massive star's life. Some of these could be seen for many months, even during the daytime despite the vast distances between humanity and the stars. However not all of these "new stars" could be attributed to a supernova explosion. Some would have been outbursts of a nova or an explosive variable star flaring up. Some might have even been the shortlived flashes of an elusive gamma ray burst, it is a possibility that the Star of Bethlehem might have been this.

In what might be the earliest recorded sighting of a supernova, the population of China was gripped in the fervour of the appearance of a bright new star near Centaurus in 185 AD.

RCW 86 is the probable remnant of this supernova. Research and analysis of X-ray data suggests this to be the case. The velocity of the gases inside the shell as well as the radius seem to correlate to this date.

Other supernova remnants visible from the south include the well known Vela Supernova Remnant as well as the lesser known RCW 103 in Norma and SN 1006 in Lupus.

Lo 5:

Another one of the multitude of planetary nebulae found in this constellation is one of the most faint and obscure. If you're wondering, the abbreviation is short for 'Longmore' as this nebula was discovered on a photographic plate by AJ. Longmore in 1976.

As the method of discovery suggests, it is an almost impossible visual object but through the rigours of astrophotography, a fairly large yet dim shell of gas will be revealed. Two red jet like structures facing each other can be found near the edges, these might have both been formed at the same time, possibly ejected by the central star. Also many foreground stars are found in front of the nebula. Long exposures will also show multiple background galaxies that always tend to seem more distant when seen near planetary nebulae.