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Sky Guide for October 2007

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Sky Guide for October 2007.

Planets. ALL TIMES GIVEN ARE GMT.

Mercury, Moves from an evening to a morning object this month. Inferior conjunction is on the 23rd. Mercury is not observable this month.


VENUS

[/td]1st Oct 15th Oct 30th OctMagnitude-4.53 -4.46 -4.37Size34" 28"24"Disc Illumination33.62% 43.18% 51.74%

Reaches greatest western elongation at the end of the month. The moon is close on the 7th, and Saturn close by on the 15th! Currently in Leo, Venus rises around 2am – which is nearly 4 hours before the sun! If you get up any time after about 3am – you cannot miss it, just look in the east.


MARS

1st Oct 15th Oct 30th OctMagnitude-0.1 -0.31 -0.6Size9.8" 11"12"Disc Illumination86.83% 88.14% 90.32%

Is currently in Gemini. The Moon is close at the beginning and the end of the month.


JUPITER

1st Oct 15th Oct 30th OctMagnitude-1.99 -1.93 -1.87Size35" 34"33"Disc Illumination99.24% 99.4% 99.59%

Setting very early now. If your lucky you’ll catch a glimpse very early in the evening in the SW. Setting by 7pm at the end of the month.


SATURN

1st Oct 15th Oct 30th OctMagnitude+0.74 +0.78 +0.80Size17" 17"17"Disc Illumination99.91% 99.84% 99.78%

Is starting to rise quite early now. Currently in Leo and rising around 1am. Moon close by on the 22nd.


URANUS

1st Oct 15th Oct 30th OctMagnitude+5.74 +5.75 +5.77Size3.7" 3.7"3.6"Disc Illumination99.99% 99.99% 99.99%

Is currently in Aquarius. Setting around 2am at the end of the month, with the moon close by on the 22nd October.


NEPTUNE

1st Oct 15th Oct 30th OctMagnitude+7.85 7.87 +7.89Size2.3" 2.3"2.3"Disc Illumination99.99% 99.99% 99.99%

Is in Capricornus. Setting before midnight at the end of the month and the moon is close o the 20th.


PLUTO

1st Oct 15th Oct 30th OctMagnitude+14.03 +14.04 +14.05Size0.10" 0.10"0.099"Disc Illumination99.99% 99.99%

Is in Sagittarius. It’s small and faint! Good Luck


HERCULES

image.jpg]

? Herculis (Ras Algethi), is from the Arabic for kneeling mans head. Ras Algethi is a red giant with a spectral glass of M5. It is a double star and was resolved in a telescope as early as 1779 by Maskelyne. The primary is 800 times larger than our sun and the second component is another giant, intense blue. The whole system is about 540 light year distant.

? Herculis (Antilicus or Rutilicus), the meaning of these names are uncertain. This is another giant star with a spectral glass of G8 – it has an apparent magnitude of 2.81, with an absolute magnitude of -0.2, and lies at a distance of 125 Light Years.

? Herculis is a dwarf star, type A6. It is 142 light years away. The apparent magnitude is 3.79 with an absolute magnitude of 0.6.

? Herculis (Sarin). This is a blue star, with a spectral type of A3. It’s apparent magnitude is 3.16 and absolute magnitude of 0.6. It is 105 ears distant.


M13, Globular Cluster. Discovered by Edmond Halley in 1714.

Messier 13 (M13, NGC 6205), also called the 'Great globular cluster in Hercules', is one of the most prominent and best known globular clusters of the Northern celestial hemisphere.

It was discovered by Edmond Halley in 1714, who noted that 'it shows itself to the naked eye when the sky is serene and the Moon absent.' According to Charles Messier, who catalogued it on June 1, 1764, it is also reported in John Bevis' "English" Celestial Atlas.

At its distance of 25,100 light years, its angular diameter of 20' corresponds to a linear 145 light years - visually, it is perhaps 13' large. It contains several 100,000 stars; Timothy Ferris in his book Galaxies even says "more than a million". Towards its centre, stars are about 500 times more concentrated than in the solar neighbourhood. The age of M13 has been determined by Sandage as 24 billion years and by Arp as 17 billion years around 1960; Arp later (in 1962) revised his value to 14 billion years (taken from Kenneth Glyn Jones).

According to Kenneth Glyn Jones, M13 is peculiar in containing one young blue star, Barnard No. 29, of spectral type B2. The membership of this star was confirmed by radial velocity measurement, and is strange for such an old cluster - apparently it is a captured field star.

SOURCE: SEDS Messier Catalogue online database

M92, Globular Cluster. Discovered 1777 by Johann Elert Bode.

Globular cluster Messier 92 (M92, NGC 6341) is one of the more conspicuous globular clusters. Situated in constellation Hercules, it is nevertheless second only within that constellation, after bright M13.

M92 is one of the original discoveries of Johann Elert Bode, who found it on December 27, 1777. Charles Messier independently rediscovered it and cataloged it on March 18, 1781, the same day as he cataloged another 8 objects, all of them Virgo Cluster galaxies (M84-M91). It was William Herschel who first resolved it into stars in 1783.

According to newer sources, M92 is about 26,000 light years distant, only little more than its brighter apparent neighbor M13. From its HRD (or CMD), it may be a bit younger than M13 as its turnoff point is shifted to the brighter and bluer end. A semi-recent estimate of M92's age has given a value of about 16 billion years (anyway more than 14 billion years), see e.g. the diagram in Sky & Telescope, January 1996, p. 22 (text on p. 20). However, this value is now again under discussion because of the general modifications of the distance scale of the universe, implied by results of ESA's astrometrical satellite Hipparcos: These results suggest that M92, as well as most other globular clusters, may be at a 10 per cent larger distance; therefore, the intrinsical brightness of all their stars must be about 20 % higher. Considering the various relations which are important for understanding stellar structure and evolution, they should also be roughly 15 % younger, in a preliminary off-hand estimate (or about 12-14 billion years). For M92, W.E. Harris' globular cluster database lists an only little modified value of 26,700 (former 26,100) light years, though, so that the quoted result might stay valid after all.

M92 is a splendid object, visible to the naked eye under very good conditions and a showpiece for every optics. It is only slightly less bright but about 1/3 less extended than M13: its 14.0' angular extension corresponds to a true diameter of 109 light years, and may have a mass of up to 330,000 suns.

Only about 16 variables have been discovered in this globular, 14 of which are of RR Lyrae type, while one of them is one of the very few eclipsing binaries in globular clusters, of W Ursae Majoris type. Although Burnham claims it is not well understood why eclipsing binaries are so rare in globulars, it appears to the present author that there may be a simple answer: In these dense stellar agglomerates, close encounters occur frequently, so that binary systems will be disturbed, and on the long term, will be destroyed.

M92 is approaching us at 112 km/sec.

SOURCE: SEDS Messier Catalogue online database

NGC 6229, Globular Cluster. Discovered on May 12, 1787 by William Herschel.

Globular cluster NGC 6229 was discovered by William Herschel on May 12, 1787, and first taken for a planetary nebula from his visual impression. Thus he cataloged it as H IV.50. John Herschel apparently never observed it, and Admiral Smyth also saw it as a nebula, and mentions that tt was taken for a comet in 1819. William Huggins found its spectrum to be continuous. It was only revealed as a "very crowded cluster" by d'Arrest in the mid 19th century. Dreyer's NGC lists it as globular cluster.

The difficulty to resolve this cluster becomes reasonable when looking at its large distance of about 100,000 light years.

SOURCE: SEDS Messier Catalogue online database

Other objects marked on the map NGC 6210, Planetary Nebula and IC 4593, Planetary Nebula.


Double Stars in Hercules

Alpha Hercules STF2140Aa-B (64 Herc) RA: 17h14m38.80s DE:+14°23'24.0"

Magnitude: 3.48/ 5.40 Distance 400 LY HR 6406 HD156014

RASALGETHI: The Kneelers Head

A beautiful colour contrast pair in the South East corner of Hercules. The Primary is an orange colour and the secondary can be seen as either blue or green. The pair is split at x100 in a moderate scope but a small scope may require higher magnifications to split. The Primary is a very late type bright giant of spectral class M5. The secondary is a close double that cannot be split visually the 2 spectral types are G5 & F2. The pair are just under 5” apart with the secondary art 112o (ESE) and do form a binary pair with an orbital period of 3600+ years. The duplicity of this star is credited to William Herschel (1779) but he stated that Neville Maskelyne noted this 2 years previously.

Delta Hercules STF3127 Aa-B (65 Herc) RA: 17h15m01.90s DE:+24°50'21.0"

Magnitude 3.14/ 8.30 Distance 95LY HR 6410 HD156164

Sarin

This pair is an optical double where 2 stars lie along the same line of sight but are totally unrelated. Delta is heading south and its companion west. The colours on this pair show a subtle contrast varying from violet/pale yellow for the primary too bluish-green to ruddy purple for the secondary. I have noted them as pale yellow and grey/green. The primary is a spectral class A3IV sub-giant and the secondary is a G4 main sequence star a little dimmer than the Sun. The pair can be easily split with medium magnification x100 as they are separated by 11” the secondary lies in a (WNW) direction at 282o.

Rho Hercules STF2161 Aa-B (75 Herc) RA: 17h23m41.00s DE:+37°08'45.0"

Magnitude: 4.50/ 5.40 Distance 402LY HR 6485 HD157779

The primary of this pair is a B class giant of spectral class 9.5III with the secondary an A (A0V) class main sequence star that has nebulous lines in its spectra. This pair is a fairly close double that will require around x100 to split in a 6 inch or larger scope. Smaller scopes may require more x150 or higher the secondary can be found about 4” away at position angle 320o (NW). The stars are evenly matched and appear white, with the primary sometimes having a bluish tint. The pair can be found just off the top left corner of the keystone, close to Pi Herc. The field is rather barren

STF2194 AB RA: 17h41m05.50s DE:+24°30'47.0"

Magnitude: 6.51/ 9.28 Distance 670LY HR 6592 HD160835

This is an easy pair for any size telescope and show a good colour contrast. The primary shows a strong orange colour as a K class giant whilst the secondary is a pale cream F4 main sequence star. The field is fairly rich and shows a cascade of stars from south west to north east. This is an optical pair, with the fainter star being twice as distant as the primary. The pair is currently just over 16” apart with the secondary lying at 7o (N). The separation has only changed by 2” since William Herschel discovered them in 1783 but the PA has changed by 13o as both have similar proper motions but one is headed north and the other NNW.

95 Hercules STF 2264 RA: 18h01m30.40s DE:+21°35'44.0"

Magnitude: 4.85/ 5.20 Distance 470LY HR 6730 HD164669

Another showpiece double, this pair is in a very rich field with many fainter stars. This pair of stars has caused controversy about their colours with blue, green, orange, silver & gold being quoted. Currently both stars appear white but the secondary has a warmer tint. They will require a moderate power to split as the secondary is around 6” away at a PA of 257o (WSW) The primary is an A5 giant star with nebulous lines and the secondary is a G8 giant. They were first observed by William Herschel in 1781. The pair is believed to be gravitationally bound but have not shown any significant orbital motion.


Legends of Hercules.

Hercules: earliest descriptions of the constellation identify it as Engonasi, the kneeling one. Its representation of the most famous of Greek heroes, Hercules, wasn't recognized by astronomers in their stellar catalogs until well after 300 BC when Herodotus' uncle, the historian Panyassis sought to add another of the Argonauts to the stellar vault in the fifth century BC. Hercules wasn't connected with this constellation for several more years. For a star group so close to Thuban, the pole star of 2700 BC, surprisingly little history survives.

Mesopotamia: representation of Marduk, the patronal god of the city of Babylon in Ur whose cult replaced the cult of Bel. Marduk was the most popular Babylonian god in the fourteenth century BC and was considered the god from which all others derived their power. His popularity arose from his triumphant duel with Tiamat, the celestial Dragon, as he created all from Chaos. He is said to have brought order from Chaos when he slew the Dragon with his mace and cut her body into two parts. One part was placed above and became the heavens, one he placed below his feet and became the earth. Her breasts became the mountains, the Tigris and Euphrates flowed from her eyes, the sea sprang from her body, her blood was oil. He then made a path for the sun to follow, divided time into a calendar of twelve months of thirty days each and created man from the bones of Qingu, ally of and lover to Tiamat. All ziggurats were dedicated to Bel-Marduk. The most famous ziggurat, Esagila, in the city of Babylon became famous as the Tower of Babel.

Greece: the legend of Hercules is perhaps one of the most well known stories in classical Greek mythology. The assignment of the constellation as Hercules was first depicted in a star atlas in 1485 in Venice. The figure appears in all illustrations with various trophies of his labors including his club, the Nemean lion's skin, the golden apples of the Hesperides, and the three heads of Cerberus, among others.

Hercules was the son of Zeus and the mortal woman Alcmene, the granddaughter of Perseus and Andromeda. Hera, Zeus' wife, was understandably jealous of this tryst and plotted to kill Hercules when he was a child. All of her plans, including a giant snake sent to crush the infant, failed miserably. Reaching manhood, Hercules performed many feats of valor. For liberating Thebes from the Minyans, he was awarded the hand of Megara, Princess of Thebes. After three sons were born, Hera saw an opportunity for revenge. She made Hercules temporarily insane and he killed Megara and the children. For this terrible crime Hercules was to pay an equally terrible price. He became a slave to Eurystheus, King of Mycenae, who consulted with Hera to devise a list of twelve impossible tasks. Only if he successfully completed these tasks would he be cleansed of his crime.

The first of the Twelve Labors of Hercules was the slaying of the Nemean lion who roamed the valley of Nemea killing people and cattle. The only weapon Hercules had to overcome the brute was his strength. It took 30 days to strangle the animal. He removed its skin and returned to Eurystheus who trembled at the sight. Hercules took the lion to the sky and nailed the body in place with stars. He wore the lion's skin as a trophy.

Hydra was a many-headed sea snake who lived in the marshes of Lerna. It was the second task. When he found that cutting off one head meant two would grow in its place, Hercules burnt the heads off instead. The final head was immortal and was buried beneath a rock. As Hercules battled the snake, a tiny crab pinched his toes. (Thank you Hera!) He crushed the animal beneath his foot. Hera pitied the noble creature and placed it in the sky along the ecliptic.

The eleventh of Hercules' tasks was the theft of the golden apples of the Hesperides. Ladon, the dragon, was the guard of the tree that held the magical fruit. With no means of defeating the beast, Hercules asked the Titan Atlas for his assistance. Since Atlas was an immortal and the father of the Hesperides, he could approach the dragon with no difficulties. Atlas, who holds the heavenly vault on his shoulders, gave up his burden to Hercules and quickly returned with the apples. He did not, however, have any intention of returning to the punishment given to him by Zeus following the downfall of the Titans. Hercules assured Atlas that he had every intention of continuing to hold up the heavens but that he needed to put a pad on his shoulders to make it more comfortable. While Atlas took the heavens back, Hercules picked up the golden apples and left.

The constellations surrounding Hercules include Boötes as the Titan Atlas with the inclusion of the Corona Borealis as the globe on the giant's shoulders, Leo as the Nemean lion, Cancer the crab, Hydra the sea serpent and Draco as the defeated dragon, Ladon, who protected the golden apple tree of the Hesperides.


PEGASUS

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? Pegasi, “Markab” which is Arabic for Saddle, is a star of spectral group B9. It shines at magnitude 2.57; the absolute magnitude is 0.1. This star lies at a distance of 103 Light Years

? Pegasi, “Scheat” which means shoulder, is a giant star of spectral type M2 in which the absorption bands produced by molecules and lines of metals are most intense. This star lies at a distance of 173 Light Years and shines at a magnitude of 2.61. It is in fact a variable star which ranges in magnitude between 2.4 and 2.8.

? Pegasi, “Algenib”, (in Bayers atlas it denotes the horses wing). It is a star 470 light years away. The spectral class of this star is B2, with a brightness of 2.87, at 10 parsecs it would be as bright as -2.8.

? Pegasi, “Enif”, is a super giant 820 light years which seen from Earth is magnitude 2.54. At a distance of 10 parsecs (36.16 Ly) it would be one of the brightest stars in the sky.

? Pegasi, “Homam”, is 180 Light years away shines at a magnitude of 3.61. It has a spectral class of B8.

? Pegasi, “Matar”, is a yellow giant G2. Lying around 230 Light years distant. With an apparent magnitude of 3.1.

M15, Discovered by Jean-Dominique Maraldi in 1746.

Globular cluster Messier 15 (M15, NGC 7078) is among the more conspicuous of these great stellar swarms. At a distance of about 33,600 light years, its diameter of 18.0 arc min corresponds to a linear extension of about 175 light-years, and its total visual brightness of 6.2 magnitudes corresponds to an absolute magnitude of -9.17, or roughly 360,000 times that of our sun. Its brightest stars are about of apparent magnitude 12.6 or absolute magnitude -2.8 or a luminosity of 1,000 times that of our Sun, and its horizontal branch giants are about of magnitude 15.6. Its overall spectral type has been determined as F3 or F4. The globular cluster is approaching us at 107 km/sec.

In amateur instruments, M15 appears somewhat smaller, perhaps about 7 arc minutes visually and 12.3 arc minutes photographically. On the other hand, the tidal radius of this globular cluster, beyond which member stars would escape because of the Milky Way galaxy's tidal forces is a bit larger: 21.5 arc minutes, corresponding to a distance of 210 light years from the cluster's center.

This globular cluster has the third rank in known variable star population, after M3 and Omega Centauri; a total of 112 variables have been identified. One of them is apparently a Cepheid of Type II (a W Virginis star).

M15 is perhaps the densest of all (globular) star clusters in our Milky Way galaxy. The Hubble Space Telescope has photographically resolved its superdense core, as shown in this HST image. M15's core has undergone a process of contraction called "core collapse", which is common in the dynamical evolution of globulars; of the 150 known globular cluster within our Milky Way Galaxy according to W.E. Harris' database, 21 have been found to contain a collapsed core (among them, besides M15, the Messier globulars M30 and M70), and there are 8 more candidates, among them M62. This central core is extremely small compared to the cluster, only about 0.14 arc minutes (8,4 arc seconds) in angular diameter, corresponding to a linear extent of roughly 1.4 light years. The half-mass radius is 1.06 arc min, or linearly about 10 light years - half the mass of this cluster is concentrated in the innermost sphere of that radius. It is still unclear if the central core of M15 is packed so dense simply because of the mutual gravitational interaction of the stars it is made of, or if it houses a dense, supermassive object, which would be resembling the supermassive objects in galactic nuclei. The one in M15 would among the nearest and better observable to us, being only little more remote than the Galactic Center and much less obscured by interstellar matter. Although the true nature of these objects remains obscure for the moment, many scientists believe they are strong candidates for "Black Holes".

M15 was discovered by Jean-Dominique Maraldi (Maraldi II, 1709-88) on September 7, 1746 while he was looking for De Chéseaux' comet; he described it as 'A nebulous star, fairly bright and composed of many stars'. Charles Messier, who cataloged it on June 3, 1764, and Johann Elert Bode couldn't make this out and described it as 'nebula without stars,' so that it remained to William Herschel in 1783 to resolve this fine star cluster.

M15 was the first globular cluster in which a planetary nebula, Pease 1 or K 648 ("K" for "Kuster"), could be identified (Pease 1928, on photographic plates taken at Mt. Wilson in 1927). Leos Ondra has provided more information on this planetary nebula. In 1976 Peterson has reported a possible second planetary nebula in this globular, situated near its center, which was however never confirmed since (thanks to Leos Ondra for pointing out this fact), so that Pease 1 remains one of only four known planetary nebulae in Milky Way globular clusters.

Moreover, globular cluster M15 contains the considerable number of 9 known pulsars, neutron stars which are the remnants of ancient supernova explosions from the time when the cluster was young. These have the designations PSR 2127+11, as well as PSR 2127+11 A to 2127+11 H. The most interesting of these objects is PSR 2127+11 C, which is apparently a component of a neutron star binary, i.e. it has a companion which is also a neutron star (S.B. Anderson et.al., Nature 346:42 (1990), T.A. Prince et.al., ApJL 374:L41 (1991)). This system, like similar ones such as the famous Hulse-Taylor binary pulsar PSR 1913+16, or the lone-standing galactic binary pulsar PSR 1534+12, is of particular interest because they exhibit strong general-relatistic gravitational effects (and is thus a natural laboratory to test Einstein's General Relativity Theory) such as significant perihelion shifts, effects on light, and emission of gravitaional radiation. The latter effect, the emission of gravitational radiation, carries away rotational energy and causes a slowdown of the pulsar frequency as well as of the orbital period.

M15 can be found extremely easily: Find the 2nd mag star Epsilon Pegasi, and Theta Pegasi SE of it. Follow the line from Theta over Epsilon and find M15 3 1/2 deg W and 2 1/4 deg N of Epsilon. A 6th mag star is about 20' away to the East, another one of mag 7.5 about 5' to the NNE.

With its apparent visual brightness of magnitude 6.2, M15 is about at the limit of visibility for the naked eye under very good conditions. The slightest optical aid, opera glass or small binoculars, reveals it as a round nebulous object. It appears as a round mottled nebula in 4-inch telescopes, with at best the very brightest stars visible, but otherwise unresolved in a fine star field. In larger telescopes more and more stars become visible the outer parts are resolved, with a more irregular, non-circular outline. The compact core, however, stays unresolved even in large amateur telescopes, but the brightest stars can be glimpsed even there. Chains and streams of stars seem to radiate out of this core in all directions, but less concentrated toward the West.

SOURCE: SEDS Messier Catalogue online database

NGC7331 Discovered by William Herschel in 1784.

NGC 7331 is one of the brighter galaxies which is not included in Messier's catalog. It exposes a fine spiral structure despite its small inclination from the edge-on position. Several companions and background galaxies are visible even in our photo.

NGC 7331 was among the earliest recognized spiral galaxies, and listed by Lord Rosse in his list of 14 "spiral or curvilinear nebulae" discovered before 1850.

One supernova has been discovered in NGC 7331 so far: SN 1959D, discovered by Milton Humason at 32"W and 13"N of the galaxy's nucleus. This supernova became as bright as 13.4 mag (see IAUC 1682 and PASP 105, 1250).

SOURCE: SEDS Messier Catalogue online database

NGC 7331 is contained in the SAC 110 Best NGC List. In the RASC's Finest N.G.C. Objects Objects list. Caldwell 30 in Patrick Moore's list.

SOURCE: SEDS Messier Catalogue online database

NGC7217 Aproximately 4 arc minutes is size and shining at a magnitude of 10.2. This galaxy has very tight spiral "structure"- however, no one feature extends long enough to be a spiral arm. This galaxy sports a curious ring of dust (dark circle) that surrounds the nucleus. It is estimated that this galaxy is around 41 million light years away. Note the very subtle difference in color between the inner yellowish region is outer bluish arms.

SOURCE: SEDS Messier Catalogue online database

NGC7457, Is a galaxy of magnitude 10.8 and is around 4.4 arc mintes in size.

NGC7441, Galaxy NGC 7741 is a barred spiral galaxy of type SB(s)cd, meaning that it has a central bar-like concentration, evident here, and a small number of fairly open large-scale spiral arms. NGC 7741 is quite nearby, and is receding from us at only 1.7 million miles per hour. (Distance: 30 million ly)

SOURCE: SEDS Messier Catalogue online database

NGC7332 / 7339, This pair of galaxies is in the constellation Pegasus. A dynamically isolated binary system (number 570 in the catalogue of double galaxies compiled by Igor Karachentsev), NGC7332 and 7339 are too far apart for obvious interaction (such as tails and streamers), although they are almost certainly orbiting around each other.

NGC7332 is the brighter galaxy to the right (west) of the image. It shows evidence of partial dust lanes, has an extended envelope and possesses a compressed, bright, box-like central bulge. It is classified S0(pec), being an intermediate lenticular galaxy, and its peculiar tag refers to the unusual box-like shape of the central region (sometimes called peanut-shaped).

The accompanying NGC7339 is seen edge-on and is thought to be of type Sbc (a mixed spiral), but its orientation makes it hard to classify exactly. It is also somewhat dimmer than its companion, although at a distance of about sixty million light-years, neither is visible to the naked eye.

Receding from us at over eight hundred miles per second, they are orbiting each other at about sixty miles per second. This isn't as fast as it sounds for galaxies which are about a million trillion miles across.

SOURCE: SEDS Messier Catalogue online database

NGC7177, is another galaxy. Magnitude 11.2 and a size of 3.3 arc minutes.

NGC7814, This is a fantastic edge-on spiral galaxy. First, the plane of the galaxy is slightly warped and twisted. NGC 7814 is one of a few bright galaxies that shows this feature in optical wavelengths. Second the number of background galaxies in this direction is impressive. Besides being pretty, these far off beacons have been used by astronomers to try to determine the amount of gas and dust in the halo of NGC 7814. As the light of background galaxies passes through the foreground halo of NGC 7814 it becomes dimmer (redder). Finally, be certain to note the very slight deviation from being truly edge-on.

SOURCE: SEDS Messier Catalogue online database

NGC7479, Discovered by William Herschel in 1784.

Supernova 1990U occurred in NGC 7479 on July 27, 1990 at 22"W and 54"S of the galaxy's nucleus. It was detected by Pennypacker, Perlmutter and Marvin, and reached mag 16 (see IAUC 5063 and AJ 111, 2017 [1990]).

Caldwell 44 in Patrick Moore's list.

SOURCE: SEDS Messier Catalogue online database


Double Stars in Pegasus

1 Peg STFB 11 AB RA: 21h22m05.20s DE:+19°48'16.0"

Magnitude: 4.20/ 7.56 HR 8173 HD203504

An easily split double for small scopes at a power of x50 or less. This pair can be found about 10o

North east of Epsilon Peg the pair was first noted in 1780 by William Herschel. The primary is a K1 type giant star that appears pale yellow with the secondary a blue/grey, this gives a pleasant and subtle colour contrast. Despite the distance between the components of nearly 36” the pair is considered to be gravitationally connected. The secondary is located at 312o (WNW) of the primary. On nights of good transparency the field is full of faint stars.

3 Peg STFA 56 AB RA: 21h37m43.60s DE:+06°37'06.0"

Magnitude: 6.18/ 7.50 HR 8265 HD205811

Another pair noted by William Herschel this time in 1782 it is an easy pair for small scopes and it can be split at a power as low as x33. The components of this pair are fairly evenly matched pair and appear white although the secondary does appear to have a slightly warmer tint. The separation is wide at over 38” with the secondary at 349o (NW). The primary is an A2V class main sequence star and the secondary is of a very similar type. This field is also rich in background stars although they are very faint.

STF2978 RA: 23h07m27.70s DE:+32°49'31.0"

Magnitude: 6.35/ 7.46 HR 8798 HD218395

Located 4o north of Beta Pegasi is another pair well matched in apparent magnitude. The colour contrast is strong of cream and blue. Although this pair are only about 8” apart a small scope with medium magnification of x100-x150 should provide a clear split. The primary is an A2V main sequence star with the secondary at 145o. The primary is noted as a variable V0343 Pegasi but the change is only about ¼ of a magnitude, observable but tough. The pair was first discovered by Struve in 1830.

37 Peg STF2912 RA: 22h29m58.00s DE:+04°25'54.0"

Magnitude: 5.70/ 7.59 HR 8566 HD213235

This is a pair for a large scope. With an 8” scope at high magnifications (x300) you will be able to see the pair elongated but not split. This is a gravitationally bound pair with a period of 120 years. This value has been revised recently from 140 years. The orbit is highly inclined and does not appear circular, the secondary appears to move directly towards and then away form the primary. The stars are F2V main sequence stars and appear creamy/white. The pair is currently separated by less than 0.5” with the secondary at 121o, as the secondary closes in to periastron the position angle will change significantly and can be followed in large scopes. The pair lie around 165 light years away and an interesting fact is that the area covered by the orbit of the pair is very similar to the size of the solar system at 40AU.


Legends of Pegasus.

Pegasus: this constellation is visible from July through January as a much larger version of Ursa Major on the opposite side of the pole star. Like many other star groups, its history maps a changing importance as the precession of the equinoxes has shifted the sky. In 5000 BC, the Great Square of Pegasus was positioned above the arch of the Milky Way exactly on the meridian on the evening of the equinox. This placement earned it the position of Paradise, where souls congregated after following the arch of the galaxy into the sky. By the third century BC, the constellation was no longer associated with Paradise and was already described as a winged horse. It is depicted upside down in relation to the surrounding constellations.

Greece: Pegasus was born with the warrior Chrysaor from the neck of Medusa after Perseus decapitated her. Medusa was a beautiful priestess who caught the eye of Poseidon. He seduced her, disguised as a stallion, in a temple consecrated to Athena. The irritated goddess changed the woman into a horrific monster who could turn men to stone if they looked at her face. Pegasus was eventually tamed by Bellerophone. One explanation for the inverted position of the horse in relation to surrounding constellations was made following Bellerophone's attempt to reach Mount Olympus on the back of the horse. Trying to stop him, Zeus sent a horsefly to sting Pegasus. Startled, Pegasus bucked and threw Bellerophone from his back. The constellation depicts the horse in the act of bucking. If, however, the horse is drawn upright in relation to the other constellations, the front legs of the animal rest on the pale in Aquarius' hands from which flows the Fluvius Aquarii in which Piscis Austrinus is swimming. This representation makes sense since legend names Pegasus as having brought forth the fountain of Hippocrene on Mount Helicon with the kick of his hooves. Could some ancient astronomer have inadvertently inverted the animal?

India: in the Rig-Veda of 3000 BC several references are made to the Aswin, the twin sons of the sky Dyaus, and brothers of Usha the Dawn. The Aswin were gods with horse heads. The importance of the depiction of the celestial horse is realized when the position of the constellation on the night of the equinox is reconstructed. The feet of the horse appear to hit the moon on this evening, spilling soma, the drink of the gods into the vessel held by Aquarius. Horses were sacred animals whose sacrifice was considered the ultimate complement to the gods.

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