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Astronomy - Interesting Q & A

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PeiWen
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  #1 Old 17-03-2004 Default Astronomy - Interesting Q & A

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Q: How long do stars usually live?

A: The length of a star's life depends on how fast it uses up its nuclear fuel. Our sun, in many ways an average sort of star, has been around for nearly five billion years and has enough fuel to keep going for another five billion years. Almost all stars shine as a result of the nuclear fusion of hydrogen into helium. This takes place within their hot, dense cores where temperatures are as high as 20 million degrees. The rate of energy generation for a star is very sensitive to both temperature and the gravitational compression from its outer layers. These parameters are higher for heavier stars, and the rate of energy generation--and in turn the observed luminosity--goes roughly as the cube of the stellar mass. Heavier stars thus burn their fuel much faster than less massive ones do and are disproportionately brighter. Some will exhaust their available hydrogen within a few million years. On the other hand, the least massive stars that we know are so parsimonious in their fuel consumption that they can live to ages older than that of the universe itself--about 15 billion years. But because they have such low energy output, they are very faint.

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Q: What is a blue moon?

A: A "blue moon" once meant something impossible or at least highly unlikely, much like the expression "when donkeys fly!" This was apparently the usage as early as the 16th century.
Then in 1883, the explosion of Krakatau in Indonesia threw enough dust into the atmosphere to turn worldwide sunsets green and the moon blue. Forest fires, prolonged drought and volcanic eruptions can still do this. So a blue moon became synonymous with something rare—hence the phrase "once in a blue moon."
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  #2 Old 17-03-2004 Default Astronomy - Interesting Q & A

Quote:
Q: How long do stars usually live?

A: The length of a star's life depends on how fast it uses up its nuclear fuel. Our sun, in many ways an average sort of star, has been around for nearly five billion years and has enough fuel to keep going for another five billion years. Almost all stars shine as a result of the nuclear fusion of hydrogen into helium. This takes place within their hot, dense cores where temperatures are as high as 20 million degrees. The rate of energy generation for a star is very sensitive to both temperature and the gravitational compression from its outer layers. These parameters are higher for heavier stars, and the rate of energy generation--and in turn the observed luminosity--goes roughly as the cube of the stellar mass. Heavier stars thus burn their fuel much faster than less massive ones do and are disproportionately brighter. Some will exhaust their available hydrogen within a few million years. On the other hand, the least massive stars that we know are so parsimonious in their fuel consumption that they can live to ages older than that of the universe itself--about 15 billion years. But because they have such low energy output, they are very faint.

---------------------------------------------------------------------------
Q: What is a blue moon?

A: A "blue moon" once meant something impossible or at least highly unlikely, much like the expression "when donkeys fly!" This was apparently the usage as early as the 16th century.
Then in 1883, the explosion of Krakatau in Indonesia threw enough dust into the atmosphere to turn worldwide sunsets green and the moon blue. Forest fires, prolonged drought and volcanic eruptions can still do this. So a blue moon became synonymous with something rare—hence the phrase "once in a blue moon."
[/img]
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Zeroth
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  #3 Old 28-12-2004 Default

Once i saw a halo around the moon... created by the diffraction when light passed the clouds... its just a magnificent sight...
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youngyew Male
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  #4 Old 29-12-2004 Default

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Originally Posted by Zeroth
Once i saw a halo around the moon... created by the diffraction when light passed the clouds... its just a magnificent sight...
I saw a halo a few months back too!! Halo is not too uncommon, but a LARGE one is quite rare though. I took a picture of it, it fills the whole screen at the widest end of the zoom lens!
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  #5 Old 29-12-2004 Default

Saw a halo yesterday night during a power blackout...
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  #6 Old 29-12-2004 Default

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Zeroth
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  #7 Old 29-12-2004 Default

the one i saw was quite big! but it slowly shrinks and then dissapears.. its so cool! hehe! i saw another one a few month later but its relatively small.. can i see the picture?
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  #8 Old 30-12-2004 Default

I added a picture of the BIG moon halo. The moon in the picture looked slightly bigger than the original one, because of the effect of shaken tripod during the 15 second long exposure. So in fact in the photo, visually the moon halo is smaller than what I had seen in real life.
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  #9 Old 20-07-2007 Default

Halo phenomena is gorgeous....yet i haven't truly seen it before ( not to mention the picture and video clips )

Anyone saw halo in Malaysia before? Which place does halo phenomena often appear?

Ya...if possible, plz tell me also which places i can observe the mirage phenomena in the sky in Malaysia...thx!
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Zeroth
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  #10 Old 22-07-2007 Default

The halo that i saw was there by coincidence due to the correct position where i was at as well as the clouds that the light diffracted to, so it's luck.
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