The open star cluster, dominated by hot blue stars, which have formed within the last 100 million years, called the Pleiades, close to the red giant Aldebaran in Taurus.
Charles Messier measured the position of the cluster and included it as M45 in his catalogue of comet-like objects, published in 1771.
It is among the nearest to the Earth of all open clusters, probably the best known and certainly the most striking to the naked eye.
Accurate knowledge of the distance to the cluster is very important in astronomy as it is a crucial first step on the cosmic distance ladder, the calibration of the distance scale of the whole universe. The cluster is now known to lie at a distance of about 135 parsecs (440 light years).
The cluster is about 12 light years in diameter and contains approximately 500 stars in total. It is dominated by young, hot blue stars, up to 14 of which can be seen with the naked eye depending on local observing conditions. The arrangement of the brightest stars is somewhat similar to Ursa Major and Ursa Minor. The total mass contained in the cluster is estimated to be about 800 solar masses.
The cluster contains many brown dwarfs — objects with less than about 8% of the Sun's mass, which are not heavy enough for nuclear fusion reactions to start in their cores and become proper stars. They may constitute up to 25% of the total population of the cluster, although they contribute less than 2% of the total mass]. Astronomers have made great efforts to find and analyse brown dwarfs in the Pleiades and other young clusters, because they are still relatively bright and observable, while brown dwarfs in older clusters have faded and are much more difficult to study.
Also present in the cluster are several white dwarfs. Given the young age of the cluster normal stars are not expected to have had time to evolve into white dwarfs, a process which normally takes several billion years. It is believed that, rather than being individual low- to intermediate-mass stars, the progenitors of the white dwarfs must have been high-mass stars in binary systems. Transfer of mass from the higher-mass star to its companion during its rapid evolution would result in a much quicker route to the formation of a white dwarf.
2006-08-13 13:04:46
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answer #1
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answered by Anonymous
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I know, It was also impossible for Columbus to have crossed the ocean. And building a horse-less carriage... surely a pipe-dream. After all, the Romans were able to move perfectly good drinking water over hundreds of miles, over mountains and valleys WITHOUT any pumps. In America, there are still people who can't get proper drinking water, so, obviously, the Romans never existed. Of course, the rest of the world does not share your doubts. Given that the Soviets tracked the TV signal through their radio-telescopes, and that they had the ability (since 1967) to pinpoint the source of any transmission, the rest of the world already knows that the landings are real. The only problem left for Americans is that the only modern photographs of the lunar landers have been taken by American lunar reconnaissance probes. Therefore, they cannot be trusted. After all, if you have proper scientists telling you one thing, and an obviously under-medicated idiot telling you another thing, we always end up going with the guy with a tinfoil hat. The problems with Earth-based telescopes are 1) Dawes' Limit and 2) the distance from there to the Moon. Dawes' Limit: the smallest resolvable angle (A) is given by A = 116/D, where D is the diameter of the main objective (mirror or lens, does not matter) in millimetres; this gives an angle in seconds of arc (there are 3600" per degree). The largest telescope on Earth (SALT) has a major axis of 11 metres (11,000 mm). This gives it a resolution of A = 0.01" (= 0.0000029 deg.); of course, it could never achieve this resolution, because of the atmosphere. The average distance to the Moon, from Earth, is 384,400 km. Putting everything in our favor, this distance is never less than 300,000 km. Even at this distance, the smallest angle, projected onto the Moon, gives a smallest resolvable size of 300,000,000 m * sin(0.01") = 15.34 m (= a bit over 50 feet). The biggest piece left on the Moon are the lander bases, with a span of 30 feet (9 m), if you include the extended legs. The body of a lander is only 14 feet across (4.3 m).
2016-03-27 00:12:16
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answer #2
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answered by Teresa 4
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Well, it is largley a matter of personal aesthetics. You location on Earth will have some bearing too since there are spectacular objects that are only visible in the far south and southern hemisphere. The best objects are the brightest and largest so you won't need a big scope in any case. For sheer detail there is the moon. Saturn is a pleaser to everyone who sees it, especially if it's your first time.
My personal favorite deep-sky (outside our solar system) object is probably M42 the Great Nebula in Orion's sword. Doesn't matter what size your telescope (or binoculars!) this is something to savor and scrutinize. It is bright enough to see with the unaided eye, but you will have to wait a few more months before it is visible in the evening sky.
Right now the summer Milky Way is high in the evening sky. Look south towards Sagittarius there are numerous bright nebulae and star clusters. M8 and M17 are bright emission nebulae similar to winter's M42. M22 is the brightest globular star cluster visible to mid-northern latitudes, also in Sagittarius. This region is jam-packed with interesting objects since it is in the direction of our galaxy's center. Binoculars will at least show these objects, which is a good way to start before scrutinizing closer with a telescope.
If you are a new scope owner, "Turn Left At Orion" by Guy Consolomagno is a good book to learn about what you can see, and how to find them.
2006-08-13 06:33:16
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answer #3
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answered by Search first before you ask it 7
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There are so many, but one of the greatest this time of the year would be M31 The Andromeda Galaxy. I makes for a great sight because of its size and brightness. Also, you can look at the Milky Way all the way from Sagittarius to the south up through Aquila and Cygnus and Cassiopeia. One of my favorite targets is the double star Albireo in the constellation Cygnus. The stellar pair are fairly easily split into its orange and blue components with even some smaller telescopes.
2006-08-13 05:44:26
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answer #4
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answered by Shaula 7
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Wow a really hard question. It depends on what you are interested in and that is a personal opinion. So, the answer has to be general.
What ever you are interested in seeing that can be seen. That is the most interesting thing.
;-D Members of the opposite sex, wild life, (is that the same thing?) stars, nebula, etc. etc.
2006-08-13 05:54:22
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answer #5
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answered by China Jon 6
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it depends on the power of your telescope but..
looking at the moon is really cool at first, and so are the planets. but the next things are geosynchronous satellites, some of which look like stars to the naked eye. if you have a strong telescope, looking at other galaxies is incredible.
2006-08-13 05:36:43
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answer #6
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answered by Anonymous
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everything that is in the solar system that can be seen through a telescope.
2006-08-13 06:34:42
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answer #7
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answered by Anonymous
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your question i can now read your question in clarity i really have a poor eyesight but bcoz of telescope my vision is now clearer lol
2006-08-16 02:43:30
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answer #8
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answered by magneto077 2
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stars
2006-08-13 05:53:29
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answer #9
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answered by ecko_strong 2
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The earth, from a distance where you can appreciate it's total girth.
2006-08-13 05:45:29
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answer #10
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answered by Anonymous
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