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Q & A: Do we see the same stars night after night?

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Most recent answer: 09/16/2011
Q:
each night when i look up at the stars i wonder if they are the same stars i see each time? or different ones? are new stars being created in our galaxy all the time?
- james (age 14)
manchester uk
A:
Yes, except for extremely rare events which probably won't occur in our lifetimes.  There are of the order of 100 billion stars in our galaxy, the milky way.   You can see at most 2 to 3 thousand of them with your naked eye.  The rest are too far away and can only be seen with a good telescope.    Indeed, new stars are being formed from coalescing gas and dust but the current rate is very small.  When the Milky Way was young, about 8 billion years ago, the star formation rate was much larger than it is now.
Another exception is when an old star that is normally too far away to be seen by the naked eye suddenly turns into a super-nova and increases its brightness by orders of magnitude.  An example of this is when a "new star" suddenly appeared in 1054 AD, well documented by the Chinese and people of the Arab World. It is now known as the Crab Nebula. 

LeeH

(published on 09/16/2011)

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