How old is the Milky Way galaxy
[From: ] [author: ] [Date: 11-12-03] [Hit: ]
-There is no exact age for the Milky Way galaxy since it is composed of stars and other objects which all formed at different times, but we do know that Earth is 4.5 billion and the Universe is 13.7 billion years old. The oldest star cluster in our galaxy is about 12 billion years old, setting a lower limit for the milky ways age,......
Some of the oldest stars in the Milky Way are found in large stellar clusters, in particular in "globular clusters". Stars belonging to a globular cluster were born together, from the same cloud and at the same time. Since stars of different masses evolve at different rates, it is possible to measure the age of globular clusters with a reasonably good accuracy. The oldest ones are found to be about 14 billion years old.
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There is no exact age for the Milky Way galaxy since it is composed of stars and other objects which all formed at different times, but we do know that Earth is 4.5 billion and the Universe is 13.7 billion years old. The oldest star cluster in our galaxy is about 12 billion years old, setting a lower limit for the milky way's age, and it probably began forming long before that, close to 13 bya.
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You are never going to get a satisfying answer because at what point in time would you consider a group of stars and protostars bound together by gravity a galaxy? There is quite a gray area for the semantics of this question. It certainly 'began' to form as soon as the universe was cool enough for the first hydrogen atoms to form.
But is one star in a thick cloud of protostar dust a 'galaxy?" How about 2? Or 200? Or 2000? Or 20,000? There isn't a rigid definition. The mass that makes up the galaxy has, for the most part, always been bounded, more or less, to itself via gravity. So, unless you define what the minimum requirements are for something to be called a galaxy, the question cannot be answered.
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No one seems to know for sure about the age of the milky way.
Based on the oldest star found, which is 13.4 billion years old, it is estimated that the milky way should be 13.6 billion years old.
But i think they are just making sure that those figures are younger then the age of the universe which they also estimate as 13.7 billion years old.
