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| Screnshots by Stellarium 0.11 - www.stellarium.org |
| 1) ORION 2) CANIS MAJOR 3) CANIS MINOR 4) TAURUS 5) GEMINI 6) AURIGA 7) CANCER |
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 The Great Nebula.Many other much larger nebulae than M42 in Orion are known, but none offers us so intimate a view of a nearby stellar nursery. To the eye the appears as a misty patch around the central star of the line of three which form Orion's sword. Binoculars or a modest telescope will show that these three “stars” are loose groups of several individuals some of which can be seen in this photograph.The central group of stars, the Trapezium cluster, is hidden in the glow of the Orion Nebula, but these stars are responsible for producting the nebula. It is the high concentration of dust and gas in this part of the sky that has resulted in the formation of the stars, so the Orion Nebula is no random association of bright stars and dusty gas. (Royal Observatory Edinburgh). |  The Horsehead Nebula region.This distinctive red emission nebula (IC 434) is the result of radiation from Sigma Orionis interacting with the surface of a dusty cloud of gas (B 33) from which project the dark shape of the head of a horse. The bright small nebula close and left of
the Horsehead in our image is the reflection nebula NGC 2023, which must also lie in front of the dark nebula. Sigma is the second brightest star in the picture and is at about the same distance from the Sun as the nebula.The brightest star here is Zeta Orionis (Alnitak), easily visible to the unaided eye as the eastermost star in the line of three that form Orion's Belt. |
 M43 is part of the M42 Nebula complex, separated from the main core of the nebula by a dark lane called the "Fish Mouth" by observers. Having the distinct shape of a comma, M43 is illuminated by the 6.9 magnitude star n Orionis. M43 was observed by De Mairian before Charles Messier added it to his famous list. |  NGC 1973-75-77 in Orion is located just north of M42. It is an amazing complex of blue reflection nebulae mixed with dark lanes and red emission nebulae. The blue color comes from reflected starlight scattered by dust. It is often overlooked because of its spectacular neighbor, but is outstanding in its own right, being one of the brightest reflection nebulae in the sky. |
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 M 41 NGC 2287 Open Cluster Magn. 4.6 Dist. 2280 l.y. 80 stars from 7th magnitude |
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| The Pleiades, M 45, Open Cluster. The Pleiades are one of the finest and nearest examples of a reflection nebula associated with a cluster of young stars. The cluster itself is a group of many hundreds of stars about 385 light years from Earth in the northern constellation of Taurus and has been recognized since ancient times. Seven of the brightest stars are quite easy to see with the unaided eye and bear the names of the Seven Sisters, the daughters of Atlas. The nebulosity seen here is light reflected from the particles in a cloud of cold gas and dust into which the cluster has drifted. It appears blue because these tiny interstellar particles scatter blue light more efficently than the longer wavelengths of red light and it is streaky because the particles have been aligned by magnetic fields between the stars. (Royal Observatory Edinburgh). | ||
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The Crab Nebula.
M1, NGC 1952, in the constellation Taurus.
The most conspicuous known supernova remnant. This object caused Messier to begin his catalog. The supernova was noted on July 4, 1054 A.D. by Chinese astronomers, and was about four times brighter than Venus, or about mag -6. According to the records, it was visible in daylight for 23 days, and 653
days to the naked eye in the night sky.
The Supernova 1054 was also assigned the variable star designation CM Tauri. It is one of few historically observed supernovae in our Milky Way Galaxy.
The nebulous remnant was discovered by John Bevis in 1731, according to Messier, who independently found it on August 28, 1758, and first thought it was a comet. Of course, he soon recognized that it had no apparent proper motion and cataloged it on September 12, 1758. It was christened the "Crab" on the ground of a drawing made by Lord Rosse about 1844.
The nebula consists of the material ejected in the supernova explosion, which has been spread over a volume approximately 10 light years in diameter, and is still expanding at the very high velocity of about 1,800
km/sec.
It emits light which consists of two major contributions: A reddish component which forms a chaotic web of bright filaments, which has an emission line spectrum like that of diffuse gaseous (or planetary) nebulae, and a blueish diffuse background of highly polarised `synchrotron radiation', which is emitted by high-energy (fast moving) electrons in a strong magnetic field; synchrotron radiation is also apparent in other "explosive" processes in the cosmos, e.g. in the active core of the irregular galaxy M82 and the peculiar jet of giant elliptical galaxy M87.
In 1948, the Crab nebula was identified as a strong source of radio radiation. X-rays from this object were detected in 1964 with a high-altitude rocket; the energy emitted in X-rays by the Crab nebula is about 100 times more than that emitted in the visual light. Nevertheless, even the luminosity of the nebula in the visible light is enormous: At its distance of 6,300 light years (which is quite well-determined), its apparent brightness corresponds to an absolute magnitude of about -3.2, or more than 1000 solar luminosities. Its overall luminosity in all spectral ranges was estimated at 100,000 solar luminosities.
On November 9, 1968, a pulsating radio source, the Crab Pulsar (also cataloged as NP0532, "NP" for NRAO Pulsar), was discovered in M1 by astronomers of the Arecibo Observatory 300-meter radio telescope in Puerto Rico. This star is the right (south-western) one of the pair visible near the center of the nebula in our photo. It has now been established that this pulsar is a rapidly rotating neutron star: It rotates about 30 times per second! This period is very well investigated because the neutron star emits pulses in virtually every part of the electromagnetic spectrum, from a "hot spot" on its surface. The neutron star is an extremely dense object, denser than an atomic nucleus, concentrating more than one solar mass in a volume of 30 kilometers across. Its rotation is slowly decelerating by magnetic interaction with the nebula; this is now a major energy source which makes the nebula shining; as stated above, this energy source is 100,000 times more energetic than our sun.
In the visible light, the pulsar is of 16th apparent magnitude. This means that this very small star is roughly of absolute magnitude +4.5, or about the same luminosity as our sun in the visible part of the spectrum !
This object has attracted so much interest that it was remarked that astronomers can be devided into two fractions of about same size: Those who do work related to the Crab nebula, and those who don't. The IAU symposium No. 46, held at Jodrell Bank (England) in August 1970 was solely devoted to this object. Simon Mitton has written a nice book on the Crab Nebula M1 in 1978, which is still most readable and informative (it is also source for some of the informations here).
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 M37. NGC 2099. Open Star Cluster. Visual Magnitude 5.6 Membership number 150 Angular diameter 14.0" Distance 4.700 L.Y. Linear diameter 25 L.Y. Type B9 Magnitude of the brightest star 11.0 |
 |  IC 405 - Bright Nebula The Flaming Star Nebula Magn. 6 |
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 The Praesepe or Beehive Cluster M 44 - NGC 2632 - Open Cluster Dist 577 l.y. - Magn. 3.7 - 200 stars |
This famous cluster, M 44, is also called Praesepe (Latin for "manger"), or the Beehive cluster. It is also one of the objects easily visible to the naked eye, and thus known since prehistoric times. Some ancient lore is associated with it: Greeks and Romans saw this "nebula" as the manger (Greek: Phatne) associated with two asses who eat from it, Asellus Borealis, the Northern Ass and Asellus Australis, the Southern Ass.
 M 67 - NGC 2682Open Cluster Magn. 6.8 - Dist. 2.710 l.y. M67 is one of the oldest known open clusters, and by far the oldest of Messier's open clusters, being aged at 4.0 billion years. Note: This is still less than the age of our Solar System, but open clusters usually get destructed much faster. It has been calculated that M67 can expect to exist as a cluster for about another 5 billion years. Only few known open clusters were found to be older, among them probably NGC 188 (Cepheus) at about 5 billion years, longly quoted as the oldest known cluster, and NGC 6791 (Lyra), which is about 7 billion years old, and is currently the oldest known open cluster in our Milky Way galaxy. The total number of stars in M67 is probably at least about 500. |
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Partly obscured by the glare of Zeta is the curious yellowish nebula NGC 2024, the Christmas Tree emission nebula, whose energy comes from a star hidden in the dark lane, while other nebulae simply reflect the light of embedded hot stars and appear blue. (Photograph by David Malin, Anglo-Australian Telescope).
