Solar System

(The Lion)

The majestic king of the spring night sky, Leo is a bright and instantly recognisable icon of the night sky. One of the greatest aspects of Leo is that it actually resembles a lion and the main part consists of an asterism known as the Sickle. This is shaped like a backwards question mark and can easily be found as its base is marked by Leo's brightest star, Regulus. The meaning of the star's name is "little king".

In Greek mythology, Leo is the astral representation of the Nemean Lion, killing it was the first of the twelve labours that Hercules had to undertake. As with the slaying of Hydra, it wasn't a straightforward fight as the lion was impervious to conventional weapons. Finally, Hercules resorted to the brutish method of strangling it and used one of the lions claws to kill it.

There are at least half a dozen meteor showers within Leo. The major one is the Leonids, it can be seen towards the end of the year with a sporadic rate of 10 or 15 meteors per hour. Something that seems inexplicable and miraculous happens every 33 years, the activity of the Leonids becomes hypercharged and the sky explodes with literally hundreds of meteors streaking through the sky in just a matter of minutes! The last time this occured was in 1999 but it was blitzed by the incredible shower of meteors in 1966. The next time this will happen will be in 2032.

The variety of deep sky objects in Leo consists of virtually nothing but galaxies but there is also an obscure and faint planetary nebula. The collection of galaxies in the kingdom of Leo is incredibly varied and impressive. Leo is a great place for telescopic beginners to explore the myriad realm of bright galaxies, about half a dozen are Messiers and many bright galaxies are also in the New General Catalogue. As well as bright galaxies that are accessible for newcomers, there is a multitude of objects for seasoned observers to tackle with large apertures, these include faint compact groups and galaxy clusters.

    M65 and M66        
    M65 (right) and M66 (left) are two bright spiral galaxies that are part of the Leo Trio with NGC 3628. The galaxies in the trio are interacting with each other, this is exemplified by the numerous star formation visible in M66. Contrastingly M65 appears unperturbed but it has been slightly distorted.        
Image copyright S. Heutz/W. Ries (Astro-Cooperation)
M65 and M66:

Big and bright, both of these galaxies are part of the Leo Trio along with NGC 3628. They are easy to find by beginners and reveal a wealth of details with medium sized scopes. The members of the Leo Trio are interacting with each other so the whole group is catalogued as Arp 317 in Halton Arp's atlas of peculiar galaxies.

M65 is a golden brown galaxy whose orientation is somewhere between face on and edge on. What can be ascertained from the golden brown colour is that the stellar population is fairly old, the interaction with the other two galaxies might reverse this trend. Visual evidence that might indicate the production of new stars is an enormous dark dust lane that runs down the entire left side of the galaxy. It also isn't a coincidence that this side also faces M66, in other interacting pairs, star formation is usually confined to the sides of the galaxies that face each other.

M66 is a big bright spiral galaxy that has the honour of being the first Messier object in the Arp Atlas at number 16. The characteristics of the galaxy that caught the attention of Halton Arp are the elongated spiral arms that don't wrap neatly around the core, particularly the southern one that is adjacent to M65. A copious amount of star formation is occuring, this is confined to the areas where the spiral arms and the central region meet. Also if you look carefully, there appears to be a structure between the two spiral arms that looks like the stump of a third arm. This is either an illusion or M66 might have had three arms in the past and this one has been heavily distorted. Another possiblity is that it was once part of either both or one of the spiral arms.

A void of 160 000 light years separates M65 and M66 from each other, the distance between these two galaxies and NGC 3628 is almost twice as much. Even more unbelievable in relation to this is that there is a greater distance between us and the Milky Way's most distant globular cluster, AM-1 in Horologium!

Sandwich Galaxy (NGC 3628):

A truly exquisite edge on galaxy, the Sandwich Galaxy as it is popuarly referred to is a strangely beautiful example of a galaxy that wasn't catalogued by Charles Messier alongside with another galaxy in Leo, NGC 2903. What gives it the unexpected name is a huge lane of dust that billows outwards at the edges. This is caused by the gravitational interaction with the other members of the Leo Trio. Another visual indication of the interaction is a tidal tail streaming from the north of the galaxy, it is incredibly dim and is only revealed in long exposure images such as the one lower down on this page.

NGC 3628 was discovered by William Herschel in 1784, four years after Messier discovered M65 and M66. The distance of NGC 3628 is the same as the other members of the Leo Trio, a fairly close 35 million light years.

M95 is one of the finest galaxies found in Leo, a hypnotic ring encircles a bright bar with a luminous core at the heart. Two circular spiral arms stem from the ring and seem to be fairly short. In long exposure photographs, there are faint extensions that wrap neatly around the ring giving M95 the ominous appearance of a cosmic eye.

Slightly brighter than M95, M96 is a truly spectacular spiral galaxy that lies in a busy area. In fact it makes a stunning pair with M95, the beauty of the pair is accentuated as both galaxies are similar in apparent size as well as having a slightly oval complexion. M96 was also one of the very first few spiral galaxies to have been discovered, it is one of the 15 that were known to exist in 1850. Some of these spiral galaxies were found by Lord Rosse with his gargantuan 'Leviathan of Parsonstown' telescope that was a staggering 72 inch! Even more unbelievable was that Lord Rosse was an amateur astronomer, it would be unheard of an amateur in this modern age to be lucky enough to own such a beast!

Small and medium sized telescopes easily reveal the main central part that also happens to be the brightest part. The central part is 60 000 light years wide and the yellow nucleus is off centred. Surrounding this is a faint ring that can only be seen with large telescopes or in photographs. The diameter of the ring is 100 000 light years with the northern part being the thinnest. A wonderful curious coincidence is the superimposition of a background galaxy near the top left of the ring, it looks as if it is keeping the ring held in place! It is a brown edge on galaxy whose light is reddened by the dust in the ring, it might be visible in very large telescopes.


One of the few ellipticals that isn't found in the numerous galaxy clusters and compact groups that are dotted around the kingdom of Leo, M105 is easy to see with a small telescope as it shines at a magnitude brighter than 10. Visually it is fairly normal and therefore it isn't as awe inspiring as the other marvellous galaxies in Leo.

Investigative studies with the Hubble Space Telescope in 1997 uncovered the dark titanic form of a supermassive black hole, what distinguishes it from its brethren is the impressive mass that is equivalent to 50 million solar masses! In other words it is equal to the mass of 50 million stars, the amount contained in a small galaxy!

Near M105 are two other galaxies that need an increase in aperture to be seen. The one that is upper left to M105 is NGC 3384 and the one below it is NGC 3389.
NGC 3384 is like a fainter squashed version of M105 and NGC 3389 is a knotty tightly wound spiral galaxy that is the smallest of the trio.

These three galaxies along with M95 and M96 are part of the Leo I group. As with other galaxy clusters, the elliptical M105 dominates the centre and is at a distance of 38 million light years. M95 and M96 also lie at this distance, the evidence for this is a huge ring of neutral hydrogen surrounding M105 that spans 650 000 light years that M96 is interacting with. Besides these galaxies, there are a few other members in the group but studies suggest that NGC 3389 is actually more distant and not a member of the group.

NGC 2903:

Indescribable is the irridescent beauty of this barred spiral galaxy, it is impressively pleasing to the eye and you have to see it to believe it (preferably with someone's 32 inch telescope at a spring star party)! Many books,astronomical magazines and websites state that it is a galaxy that was overlooked by Messier, it is astounding that he actually missed it as it is very bright at magnitude 9. In fact it is actually the second brightest galaxy in Leo!

NGC 2903 is known as a 'hot spot' galaxy. The reason is the incredible activity that is occuring, a massive 2000 light year wide ring of luminous material encircles the core. This ring has imbued NGC 2903 with a greater star forming capability but not enough to be classed as starburst. This ring consists of highly luminous star clusters and constitutes 10 percent of the galaxy. What makes these clusters unique is that they are actually young blue globular clusters, this was uncovered by the HST. Another galaxy that contains these curious objects is the LMC in Dorado.

This isn't the only similarity shared with the LMC, many supergiant HII regions are found in the area surrounding the core. It is likely that some dwarf the gigantic tendrils of the 30 Doradus complex in the LMC, they look fairly small as NGC 2903 is 28 million light years distant. If the galaxy was one tenth the distance, they would probably rival or even exceed the giant HII regions of the LMC! The brightest one is so large that it was given an NGC designation of NGC 2905 although it was first seen by William Herschel in 1784 when he also discovered NGC 2903. NGC 2905 can be found above the centre of NGC 2903 in between the northern edge and the parts of the spiral arm that are adjacent to the core region. It is unnecessary to say that patience and steady skies are needed alongside a very large telescope to see it.

Sandwich Galaxy

The Sandwich Galaxy is perfect for satiating a ravenous hunger for galaxies after gorging on the banquet of winter nebulae, this intergalactic baguette is a hearty treat for telescopic observers!

In the upper left corner, a ghostly stream can be seen. This is a tidal tail caused by the interaction with M66, it is known that this galaxy is the progenitor of the stream as there is a large bridge of gas between NGC 3628 and M66 that happens to coincide with the optically visible stream. If you strain your eyes, you might be able to see a few blue dots towards the end of the stream, this is tidally initiated star formation.

The distance between NGC 3628 and M66 is currently 300 000 light years (to be exact the distance would actually have been 35 million years ago as this is the distance in light years of both galaxies). Research indicates that 800 million years ago, both galaxies came close to each other with 80 000 light years separation and this event sparked the unusual behaviour and deformities in both galaxies.

Image copyright R. Croman
NGC 3521:
One of the few flocculent spirals found in Leo, NGC 3521 is a wonderful galaxy that is tilted at an angle between face on and edge on. As with other examples, the spiral structure is quite patchy and ill defined and encompasses a blazing white core that is the only part visible in small telescopes. Very large apertures reveal a ghostly halo around the galaxy as well as a subtle dust lane. Overall, NGC 3521 is almost identical to NGC 2841 in Ursa Major.
Leo I:

Overpowered by the blazing blue sphere of Regulus, this dwarf galaxy happens to be placed in an unfortunate area of Leo. It can be found north of Regulus and as it is rendered almost invisible by the outpouring of light from the 21st brightest star in the sky, large telescopes can only reveal it as they would be capable of having sufficient power to place Regulus out of the field of view.

It is unsurprising that it wasn't until 1950 that Leo I was discovered by the Palomar Observatory. Despite the name, it isn't actually part of the Leo I group of galaxies, it is one of the satellites of the Milky Way and is a member of the Local Group at a distance of about 800 000 light years. It also has the designation of UGC 5470.

Hickson 44:

Some consider this grouping of four galaxies to be the best of all the Hickson groups, a huge scope is vital to prove it to yourself. The group is 60 million light years away and the members are close enough for interaction to occur.

The predominant member is the elongated edge on spiral NGC 3190, the appearance is akin to a distorted version of the Sandwich Galaxy. To the upper left is a bright elliptical, NGC 3193. To the right of this is a barred spiral called NGC 3187, the bar is the brightest distinguishing feature and is the only part visible in large telescopes. Very large telescopes or long exposure photographs show the wispy spiral arms. These three galaxies seem to make a triangle and NGC 3185, the fourth member being lower right to them. This galaxy is also a barred spiral with the tightly wound spiral arms forming a ring around the bar.

All four galaxies show signs of interaction including tidal streams and outer haloes. At some point in the foreseeable future, the four galaxies will merge into a single giant galaxy that is most likely to be elliptical. One possible scenario is NGC 3190,
NGC 3193 and NGC 3187 merging into one galaxy with NGC 3185 being a companion.

NGC 3810:
NGC 3810 is a gorgeous face on spiral galaxy that is moderately bright at magnitude 11. Four spiral arms gush from the bright yellow core giving NGC 3810 a satisfying symmetrical appearance. The arms unfortunately are rather flimsy but are dotted with a few red nebulae. The galaxy hosted a recent supernova in 2000 that was discovered by Tim Puckett. Overall NGC 3810 is like a fainter version of NGC 3486 in Leo Minor and the distance is 52 million light years.
NGC 3226-7:
Also known as Arp 94, this unconventional interacting galaxy pair will intrigue you with its unusual combination of a large spiral galaxy (NGC 3227) with the bright round glow of an elliptical galaxy (NGC 3226) attached to a spiral arm. NGC 3227 has been heavily affected as tidal shells encompass the spiral structure.
Copeland's Septet (Hickson 57):

Another one of about a dozen Hickson groups found in Leo, this faint grouping of seven galaxies was discovered by Ralph Copeland in 1874 with the 72 inch Leviathan that belonged to Lord Rosse. In fact Copeland was an assistant to Lord Rosse and quite surprising is that he made mistakes concerning the positions of the galaxies. Fortunately these errors are now non-existant and the correct position is marked on star charts.

The brightest galaxy is NGC 3753 and also happens to be the largest. It shines at a dim 13.6 magnitude, in comparison the faintest galaxy NGC 3745 is magnitude 15 and is also the smallest member of the group. NGC 3753 has an elliptical companion to the south called NGC 3750.

Very large telescopes are needed to see all members and the thrill of observing Hickson 57 originates from the fact that you are looking at a 'mini cluster' of galaxies that are hundreds of millions of light years away despite appearing as featureless spots of light.

Observations with large professional observatories are able to reveal the details of all the galaxies. A tidal tail can be seen jutting outwards from NGC 3753, it is likely that it is interacting with the barred spiral NGC 3754 above it. Adding to this is that
NGC 3754 is slightly distorted. These qualities make Copeland's Septet to be considered as peculiar and therefore is also known as Arp 320.

Abell 1367:

Abell 1367 is one of the most awe inspiring galaxy clusters that is overlooked possibly due to its faintness as well as being visible only in sizeable scopes. The cluster has a centrally dominant elliptical galaxy called NGC 3842. It is likely that NGC 3842 was once smaller than its present size and it acquired more mass due to the assimilation and devouring of any galaxies that got too close.

Other notable members include the spindle shaped NGC 3844 and a spiral galaxy called NGC 3840. Most of the galaxies shine with a ambient yellow glow although there is a blue galaxy called UGC 6697 that is orientated edge wise. It is surprising that Halton Arp didn't include this galaxy in his atlas as it has numerous qualities that warrant it as being considered peculiar. The shape isn't perfectly straight, it is slightly bent at one side and there appears to be a series of knotted regions emanating from the other side. Long exposures have revealed jet like structures that might either be tidal tails or a halo that is viewed from the side. UGC 6697 is similar to NGC 4656 in Canes Venatici although the central regions are reminiscent of the chaotic structure found in the Whale Galaxy.

Abell 1367 is situated in an interesting part of the universe. It lies at a distance of 270 million light years in the Coma Supercluster. It is also a component of the Great Wall superstructure that spans 500 million light years between Hercules and Leo.

Hickson 44      

Hickson 44 is a glorious grouping of galaxies that is relatively close compared to other compact groups. NGC 3190 is the edge on galaxy, NGC 3193 is the elliptical and the blue barred spiral is NGC 3187.
The galaxy in the bottom right corner is NGC 3185. The golden glow of hundreds of background galaxies is an astounding canvas!

The trio of galaxies at the top are currently engaged in a ferocious bout of interaction. A huge tidal plume can be seen around NGC 3190 as well as an incredibly faint tidal bridge between NGC 3190 and NGC 3193.
The spiral arms of NGC 3187 have been heavily distorted, instead of gracefully wrapping around the bar they seem to have become stretched outwards.

All members with the exception of NGC 3185 are catalogued collectively as Arp 316. The reason for NGC 3185 not being included is due to its fairly normal appearance. If you look carefully, an outer halo extends around the galaxy, it is possible this feature was not picked up by the film camera that was used to take the original atlas image. It is remarkable that amateur images taken with sensitive CCD cameras and modest apertures reveal details that would have been impossible to detect 15 years ago with professional observatories!

Image copyright R. Croman
      Leo Minor
Secret Page!