Constellations and Featured Stars

Leo is one of the few constellations that resemble what they are meant to, the shape of a lion is unmistakable. In mythology Leo represents the lion killed by Hercules as one of his twelve labours.

Leo, if not already obvious to observers, can be found by using the two “pointers of Ursa Major” in the wrong direction i.e. away from Polaris, Alpha Ursae Minoris.

Leo is also the radiant of a meteor shower between the 14^th and 20^th November, peaking on the 17^th November. Approximately every 33 years the shower becomes a meteor storm, such as last year, although observers here in the UK didn’t get a very good display due to cloud cover.

Bright Stars

Alpha Leonis: (Regulus – Stella Regina) translates as “Little King”. Regulus is the dimist of all the stars regarded as first magnitude it is in fact the 21^st brightest star in the night sky, but has always been symbolically important. The ancient Egyptians knew that the Sun entering Leo corresponded with the flooding of the Nile and no one can doubt the importance the Egyptians gave to Leo by building the Sphinx as the head of man and the body of a lion. The Indians call Regulus by the name of Magha “The Mighty”, in Persia it was Miyau “The Centre” and the Romans called it Cor Leonis “Lions Heart”.

Regulus has an apparent magnitude of 1.38, an absolute magnitude of –0.6, is of spectral type B7 and is located at a distance of approximately 85 light years. The star is a white star about 130 time as luminous as the Sun and it does have a magnitude 7.7 companion star which is itself again a close double star.

Beta Leonis: (Denebola) translates as “Lions Tail” and it is of interest because it would appear that Denebola has faded by over a magnitude, since 1603, for no apparent reason as it is a pretty standard main sequence star. It was once said to be of first magnitude but it now shines at an apparent magnitude of 2.14 although its absolute magnitude is 1.6, it lies at a distance of 42 light years and is of spectral type A3.

Gamma Leonis: (Algieba) translates as “Lions Mane” and although designated as the third brightest star in the constellation it now outshines Denebola, shining at an apparent magnitude of 1.99 its absolute magnitude is –0.4. It is a beautiful binary star with the primary component being orange and the secondary star being of yellowish appearance. Algieba is located at a distance of approximately 91 light years and is of spectral type K0 the secondary star is of spectral type G7.

Delta Leonis: (Zosma) translates as “Girdle” although its origin is unsure but is perhaps Persian. The star has an apparent magnitude of 2.56 and is located at approximately 68 light years its absolute magnitude is 0.1 and it is of spectral type A4. Zosma has a magnitude 8.6 companion star that is easily split as it is 191 arc seconds from Zosma.

Although these are the four brightest stars Leo also has several other notable fairly bright stars, these are: Epsilon Leonis (Asad Australis) magnitude 2.98 spectral class G0, Theta Leonis (Chort) magnitude 3.34 spectral class A2, Zeta Leonis (Adhafera) magnitude 3.44 spectral class F0.

Deep Sky Objects In Leo

M65: (NGC 3623) is a spiral galaxy of magnitude 9.9 and this forms a magnificent sight in even a small telescope as both M65 and M66 can be seen in the same eyepiece.

M66: (NGC 3727) is an edge on spiral galaxy of magnitude 9.9 which has an obvious dark dust band running through its centre. Both M65 and M66 are approximately 35 million light years distant and they are a true gravitationally bound pair separated by only 200000 light years, on the doorstep in galactic distance scale.

NGC 3628: lies just above M66 but is an edge on spiral of magnitude 9.9 but it is extremely difficult to locate even through the 12” LX200.

M105: (NGC 3379) is an elliptical galaxy of magnitude 9.3, observers will struggle to bring this galaxy to a sharp focus though. In the same eyepiece as M105 you can observe NGC 3384 and NGC 3389.

M95: (NGC 3351) is a barred spiral galaxy of magnitude 9.7, I must confess that although I have seen its core through a 4” scope I have seen little more of the galaxy even through large scopes.

M96: (NGC 3368) is a spiral galaxy of magnitude 9.2 and is far easier to spot than M95.

NGC 3607: is an elliptical galaxy of magnitude 10.9, above it and in the same eyepiece you can see NGC 3608 this is about a magnitude fainter.

Ophiucus – The Thirteenth Constellation of the Zodiac

Ophiucus lies on the Zodiac, and is the thirteenth such constellation, however, it is not recognised by Astrologers. It represents a serpent, Serpens, coiled round a man's, Aesculapius', body. Aesculapius is believed to have preceded Hippocrates as an early healer who was supposed to be able to raise the dead. To this day, the serpent is the medical symbol of healing.

The best known star in Ophiucus is Barnard's star, magnnitude 9.5, the second closest to our Sun, and one of the first thought to have a planetary system.

The southern part of the constellation lies in the Milky Way, looking towards the centre of our galaxy, and is a good source of star clusters and other objects. Ophiucus is the site of the last supernova seen in our own galaxy in 1604. There is also a recurring nova, RS Ophiuchi, which flares up every 20 years or so. It was last seen in 1985, 1967, 1958, 1933 and 1898. Normally magnitude 12, it brightens to naked eye visibility.

Principal stars are: Rasalhague -Alpha Ophiuchi, magnitude 2.6; Cebalrai - Beta Ophiuchi, magnitude 2.8; Yed Prior - Delta Ophiuchi, magnitude 2.7; Gamma Ophiuchi, magnitude 3.8

Barnards Star – The Celestial Sprinter

While the constellations appear fixed and unchanging over a human lifetime or two, the stars do slowly change their positions over the centuries as the Sun and the other stars move through space at various speeds and in different directions. For most stars, this change in position on the sky is very slow, indeed -- the constellations of 10,000 years ago were only slightly different from what they look like now. But stars that are quite nearby can change their positions relatively rapidly, just as a car on a street right next to you zips past you quickly, but cars on a distant highway seem to crawl along.

This star is the second nearest to our Solar System at 5.97 light years, only triple star Alpha Centauri is closer. From this distance, it follows that the fast apparent motion corresponds to an unusually high velocity. In addition, this star is approaching us rapidly at 87 miles per second, so that the combination of both indicates a space velocity of about 103 miles per second. According to Burnham, the star will reach a minimum distance of 3.8 light years in about 8,000 years, when its proper motion will have reached 25 arc seconds per year and its brightness will be about magnitude 8.6.

Barnard's star is a red main-sequence dwarf of apparent visual magnitude 9.56 and absolute visual magnitude +13.4. Its luminosity is only about 1/2500 that of our sun. The star's mass is only 16 percent that of our sun, and its diameter at 224,000 km (140,000 miles) or about 1/6 that of our sun. Its spectral type indicates that Barnard's Star is cool: Only about 3200 K.

P. Van de Kamp had announced the discovery of the presence of at least one planet of 1.5 times the mass of Jupiter at a separation of 2.4 arc seconds, or 4 Astronomical Units. However, after a decade-long discussion, this discovery could still not be verified, and more recent observations with the Hubble Space Telescope have not yet given evidence of any large planet near this star.

Deep Sky Objects in Ophiucus

M-9 This globular cluster is about 6-8' in diameter, roughly circular, with some resolution at the edges. The core is somewhat kidney bean shaped, and is elongated in the north to south direction. Under a clear, dark sky you can find Barnard 64, a dark nebula upon which M-9 is superimposed. It is a region, about 3/4 of a degree in extent, which is almost devoid of stars just to the west of the globular, and ever so slightly darker than the surrounding sky background

M-10 This globular cluster is well resolved even at low powers. It is about 12' in diameter, and has a circular shape with stars resolved across its face. A chain of 6 foreground stars starts north of the globular and ends to its south, seemingly bisecting the cluster

M-12 Lying only a few degrees away from M-10, this object is slightly smaller, about 8-10' in diameter. It is also well resolved across its face, and is somewhat looser than M10. It is basically circular and has a granular centre.

M-14 This object is about 8' in diameter, with about 200X magnification required to reveal any detail other than the granular core of the globular cluster. A 8” scope or a dark sited 6” is a must to observe this globular.

M-19 This globular appears as a milky patch of light about 8' in diameter, with resolution around the edges. Its granular core is flanked by two stars, one to the northwest, and one to the northeast, and appears somewhat oval in shape.

M-107 This moderately faint object needs a high power and averted vision to yield resolution. It is about 8' in diameter, and is slightly flattened on its northern edge. The brightest area appears is the southwestern corner of the globular.

M-62 A fine, bright globular cluster with resolution at the edges, and a bright core. About 10' in diameter, this cluster's core is slightly offset to the southeast. Stars seem to fan out to the west, giving this globular rather unique almost 3D appearance.

NGC 6369 This is a moderately bright planetary nebula which is almost 1' in diameter. It appears as a grey puff of light that, with averted vision, has a darker centre suggesting angularity (a ring shape).

Orion (The Hunter)

There are two different legends in mythology associated with Orion. According to one legend he was the son of Neptune and Euryale and he claimed he could defeat any animal the Earth could produce. Juno, who was jealous of him, caused a giant scorpion to appear from the ground and bite him thereby killing him. Diana, the goddess of hunting, pleaded he be placed in the sky opposite the scorpion (Scorpius) so that it could cause him no more harm.

The second legend is that Diana’s love of Orion angered Apollo who tricked her to demonstrate her skill at archery by shooting a distant object in the sea. She succeeded in hitting the object but it turned out to be Orion, her arrow having killed him she decided to place him in the heavens with his hunting dogs (Canis Major and Canis Minor).

Star Feature on Betelgeuse (Alpha Orionis)

Betelgeuse is a red super giant star and is the largest star known in our part of the galaxy. It is the only star that astronomers have observed surface features on, other than our own Sun, using a process called speckled interferometry at the William Herschel telescope in La Palma.

Betelgeuse is a variable star with a magnitude range of between 0.1 and 0.9 caused by the star expanding and contracting. If Betelgeuse replaced our own Sun, at its average size it would extend beyond the orbit of Mars, at maximum it would extend beyond the orbit of Jupiter. Betelgeuse is of spectral type M2 with a surface temperature of approximately 3400 degrees centigrade however, because of the mass of the star its core temperature reaches 100’000’000 degrees centigrade.

Because of the stars enormous size it will undoubtedly end its life exploding as a supernova, this will be an incredible sight depending on the time of year, it will shine as brightly as our own Sun at a magnitude expected to be approximately –26. If it occurred in wintertime, in the Northern Hemisphere, then we would not have night and day but instead would have sustained daylight for some three months until the star began to dim.

Although designated as “Alpha Orionis”, supposedly the brightest star in the constellation of Orion, it is actually outshone by Rigel (Beta Orionis). The other famous example of this incorrect labelling is Alpha Geminorum and Beta Geminorum, Castor and Pollux, although it is thought that Castor has dimmed substantially over the years.

The name of the star is Arabic and derived from the name “Ibt – al – Jauza” which when translated means “Shoulder of the Central One”. Its name has been spelt in various different formats over the years including Beldengenze, Bedalgeuze, Betelgeux, Betelgeuze and most recently Betelgeuse.

Cassiopeia

This well known constellation which represents a woman sitting in a chair is a bright constellation lying in a rich part of the Milky Way, close to the celestial north pole and easily recognised by its large “W” shape. It can be found on the opposite side of the Pole Star to the Great Bear (Ursa Major). It contains two Messier open clusters, M52 & M103 of magnitudes 7.3 & 7.4 respectively.

Cassiopeia is circumpolar, and is visible all year round in the Northern Hemisphere

A strong radio source, Cassiopeia A, emanates from this constellation. It is the remains of a supernova, 10,000 light years distant, which occurred around 1660AD

The principal stars are: Schedar - The Breast (Alpha Cassiopeiae), magnitude 2.2; Caph (Beta Cassiopeiae), magnitude 2.3; Gamma Cassiopeiae a shell star, variable, with mean magnitude 2.5; Ruchba - The Knee (Delta Cassiopeiae), magnitude 2.7

The Mythology

Cassiopeia, the wife of King Cepheus, ruler of Ethiopia, was beautiful, arrogant and vain, and it was these latter two characteristics which were to lead to her downfall. Her continual boast that both she and her daughter Andromeda were more beautiful than the sea nymphs, daughters of Nereus, the sea god, brought the wrath of Poseidon, ruling god of the sea, upon the kingdom of Ethiopia. (Differing accounts state that either Cetus, the sea monster, on Poseidon's instructions, was to destroy the land, or that the whole country was to be flooded.) Trying to avert such a fate, Cepheus and Cassiopeia consulted a wise oracle who told them that the only way to appease the sea gods was to sacrifice their daughter. Accordingly, Andromeda was chained to a rock at the sea's edge, and left there to helplessly to await her fate at the mercy of the sea monster but, Perseus arrived in time and saved Andromeda. Poseidon considered that Cassiopeia should not escape punishment entirely, and placed her in the heavens in such a position that she circles the celestial pole in an upside-down position for half the time.

Deep Sky Objects in Cassiopeia

M52

The Sky Catalogue 2000.0 gives an age of only 35 million years. The distance of this cluster is not very well known; Kenneth Glyn Jones adopts 3,000ly, Mallas/Kreimer 7,000 light years, while the Sky Catalogue 2000.0 gives 5,200 (i.e., 1,600 pc) and Götz 5,050 light years. Robert Garfinkle, in his "Star Hopping", quotes about 3,000, Harvey Pennington and George Kepple and “Night Sky Observer Guide” gives 3,900 light years. This uncertainty is mainly due to the high absorption its light has suffered on its way to us, which is complicated to estimate reasonably.

Adopting our value of 5,000 light years, the cluster's apparent diameter of 13.0 arc minutes corresponds to an extension of 19 light years.

Amateurs can see M52 as a nebulous patch in good binoculars or finder scopes. In 4-inch telescopes, it appears as a fine, rich compressed cluster of faint stars, often described as of fan or "V" shape.

M52 can be found quite easily by extending the line from Alpha through Beta Cassiopeiae to approximately one and a half time the distance between them. There is a fifth magnitude star “4 Cassiopeiae” slightly to the north west of M52.

M103

Harlow Shapley, who classified M103 as a loose and poor cluster once doubted its existance and considered it may be just an accidental grouping of physically unrelated stars at different distances. However, we now know that this cluster has at least 40 proven members and may have at least 60.

M103 is one of the remotest open clusters in Messier's catalog, at about 8,000 light years although this distance could be as great as (Night Sky Observer's Handbook) 9,200 light years. The uncertainty is mainly due to the less wellknown amount of obstruction for this cluster that lies well within the band of the Milky Way.

M103's appearance is dominated by the non-member binary Struve 131 (ADS 1209; components A, 7.3 mag, and B, 10.5 mag, nevertheless, John Herschel has always referred to this double star in context of this cluster. The cluster is thought to be approximately 22 million years o

M103’s distance of 8,500 light years and an angular diameter of 6 arc minutes corresponds to a 15 light-years linear cluster spread / extension. This stellar swarm is approaching us at 37 km/sec.

In binoculars, M103 is easy to find and identify, and well visible as a nebulous fan-shaped patch. A 10x40 finder supposedly resolves the cluster into stars; however, this is only possible under very good viewing conditions. The object is not so easy to identify in telescopes because it is quite loose and poor, and may be confused with other numerous star groups or clusters in the vicinity.

This cluster is quite easy to find from Delta Cassiopeiae (named Ruchbah), half a degree north and one degree east, close to the line to Epsilon Cassiopeiae (Segin). Situated nearby are four other open clusters, including Trumpler 1, NGC 654, NGC 659 and NGC 663. M103 is the closest cluster to Ruchbah and therefore should not be confused with the other four clusters in this compact 2 degree square patch in the sky north east of Delta.

Trumpler 1 lies about half a degree north west of M103 and is a small open cluster.

NGC 654 is an open cluster and contains about 60 stars. It lies a further 1 degree north west of Trumpler 1.

NGC 663 is an open cluster half a degree south west of NGC 654. The cluster contains about 60 stars. If observed through a medium telescope it looks similar to a globular cluster with plenty of structure

NGC 659 is the fifth open cluster which completes this little group. It was discovered by Caroline Herschel in 1783, her brother William included it in his catalogue as H VIII.65. It lies half a degree south east of NGC 663 and has a “X” shape appearance. It contains about 40 stars.

NGC 225 has been nicknamed the Sailboat Cluster, it was discovered by Caroline Herschel in 1784, her brother William included it in his catalogue as H VIII.78. This open cluster lies one and a half degrees north east of Gamma Cassiopeiae.

NGC 381 Discovered by Caroline Herschel in 1783, her brother William included it in his catalogue as H VIII.64. This open cluster lies about one degree north west of Gamma Cassiopeiae.

NGC 7789 Discovered by Caroline Herschel in 1783, her brother William included it in his catalogue as H VI.30. This is a very large open cluster covering an area equivalent to about two thirds the diameter of the full Moon. The cluster lies about four degrees south east of Beta Cassiopeiae.

NGC 7635 (Bubble Nebula)

Virgo

Updated on 12 February 2003 Next Page