Solar System

(The Dragon)

Winding its large form around the north pole, Draco has been recognised as a dragon in the sky by many different ancient civilisations such as the Chaldeans and the Greeks.

Since it was regarded by many civilisations as a dragon, there are many myths surrounding it. Since there are so many myths, only the Greek one will be mentioned.

One of the missions of Hercules the hero was to slay a dragon that guarded the Hesperides. He killed the dragon because it prevented him from gaining access to the golden apples that grew there.

Four thousand years ago, the north pole was not centred on the star we know as Polarus. Instead it was a star called Thuban that was the pole star and it is also the brightest star in Draco. The reason for this is something called precession, a motion of the Earth that causes it to wobble like a spinning top along its axis. This bizarre wobble is a direct result of the tidal effects of the Sun and the Moon. Many thousands of years in the future, Polarus will not be the north pole star just as Sigma Octantis will not be the south pole star. In fact the bright star Delta Carinae will mark the south pole. One cycle of precession takes 26 000 years to complete.

    Cat's Eye Nebula      

The full extent of the entire Cat's Eye Nebula is visible in this brilliant image. The central part is vastly familiar due to the iconic Hubble Space Telescope images but the visual appeal is greatly accentuated when the nebula is seen in all its entirety.

The knotted region to the right of the central part is so bright that it was incorrectly catalogued as a separate object and given the designation of IC 4677. The central region is the brightest part of the Cat's Eye Nebula and shines at 8th magnitude, therefore it is visible through small telescopes. This planetary nebula was discovered in 1786 by William Herschel. Click the image for a larger version.

Image copyright Capella Observatory
Cat's Eye Nebula (NGC 6543):

One of the best planetary nebulae near the north pole, NGC 6543 has many parts to it that make it an attractive celestial sight. The main nebula structure has many outer and inner filaments that form a weaving web of aquamarine and teal shades of colour. The colour is due to doubly ionized oxygen (abbreviated to OIII) being present in the nebula and is found in many other planetary nebulae such as the Little Dumbbell Nebula in Perseus. The filamentary rings showcase an age gradient, the inner rings are younger than the older ones. This is probably because the gas was ejected at regular intervals every few thousand years. Enshrouding the nebula is a massive multicoloured shell that extends for many light years that can only be seen in large aperture telescopes as well as long exposure images.

This planetary nebula was the first one to have its spectrum analysed, in 1864 by William Huggins. This determined their true nature as they were previously thought of as faint irresolvable clusters of stars and the detection of gases that were absent in stars proved otherwise.

While investigating planetary nebulae, there is a degree of uncertainty involved in determining their three dimensional structure. It is believed that many round and ring shaped nebulae actually consist of a tubular structure. It is also likely that some are actually imperfectly round spheres of glowing gas and some of the spherical ones might also be enshrouded by multiple shells.

Splinter Galaxy (NGC 5907):

Thin as the edge of a knife, the Splinter Galaxy is an edge on galaxy located 35 million light years away. A small satellite galaxy is in the process of warping the galaxy and this has caused an incredibly faint arc to loop from one end of the galaxy to the other in an elliptical manner.

From one end of the galaxy extends an even thinner part that could be a spiral arm viewed from the side rather than face on. In the sky,the galaxy lies near the
NGC 5905-8 galaxy pair.

M102 (NGC 5866):

This exactly edge on lenticular galaxy has caused a great deal of confusion over its identity, is it the 102nd entry in the Messier catalogue or is M102 a duplicated observation of the galaxy M101 in Ursa Major? The answer will probably be never found but it has the definite designation of NGC 5866.

Splitting the galaxy in the middle is a dark dust lane that has many fingers of dust adorning the edges. This dust lane is warped due to being gravitationally affected by other galaxies that share the group that M102 is part of.

Surrounding the dark dust lane is a bright disk of blue stars and surrounding the disk is a outer halo.

NGC 5905 and NGC 5908:

An eye catching pair of galaxies that serve to illustrate the differing views of a spiral galaxy caused by varying perspectives. NGC 5905 is a fabulous face on spiral, whereas on the other hand NGC 5908 is also spiral but it is inclined to an edge on view. A space of 500 000 light years separates both galaxies and they both lie at a huge distance of 140 million light years.

NGC 5905 has a central bar with two blue spiral arms attached to the ends and winding around the bar in an anti clockwise fashion.

NGC 5908 is characterised by a dark dust lane that seems to punctuate a bright blue disk.

Draco Triplet (NGC 5981, NGC 5982 and NGC 5985):
A fantastic trio of galaxies with the elliptical galaxy NGC 5982 in the centre. Not too dissimilar to NGC 6744 in Pavo, NGC 5985 is a multi armed spiral galaxy to the left side. On the right side is NGC 5981, another edge on galaxy that is similar to
NGC 5908. This group of galaxies is too small to be counted as a compact group and a minimum of four galaxies is required for a group to be considered as a compact group.
NGC 5963 and NGC 5965:
Galaxy groups seem to be ubiquitous in Draco, this offering is a very faint pair.
NGC 5963 is a spiral galaxy with a bright sky blue core and with dark blue spiral arms. NGC 5965 appears as a silver fish, this 13th magnitude edge on galaxy was host to a recent supernova in 2001. The area of these two galaxies seem to be abundant in many background galaxies that can be seen in the largest telescopes.
NGC 6742:
Draco offers quite a few ways of taking a break from observing the many galaxies found in this constellation. NGC 6742 is one such way and is a smooth green glowing orb that appears to have virtually no complex structure. On the right side opposite the central star, a foreground star is superimposed. NGC 6742 is also referred to as Abell 50.
Tadpole Galaxy (Arp 188):

The most noticeable part of this magnitude 15 galaxy is the massive tidal stream that spans a huge 280 000 light years making it longer than the tidal bridge in
Arp 295. The progenitor of the tidal tail is a blue compact dwarf galaxy, which is located below the Tadpole Galaxy. It's gravity is having such a strong effect that the tidal tail has many young star clusters attached to it. In the southern portion of the tail is a pair of blue clumps that seem detached from the main tidal tail. These might become dwarf companion galaxies millions of years from now.

Another remarkable aspect of this galaxy is its huge distance of 420 million light years away. It is amazing to say the least that this is visible in the largest of amateur scopes.

NGC 6643:
Shining at a fairly bright magnitude 12, NGC 6643 is a medium sized spiral galaxy that is characterised by its multiple spiral arms that sprout from a core surrounded by a broken inner ring. The spiral arms are knotty in texture and the galaxy is similar to the Sunflower Galaxy in Canes Venatici.
Draco Trio    
Floating in the dark jet black ether of space, the Draco Trio is the most popular triplet of galaxies visible in the night sky after the Leo Trio. From left to right: NGC 5985, NGC 5982 and NGC 5981.    
Image copyright K. Crawford