6-5-6-5-4-4-7-7-8 meter, abcbdefbf rhyme. Yep, pretty complicated, just like Nature.

I will answer manyantler\'s questions here since I think there will be others interested in the answers as well.

First, I\'d like to comment on Zeta-Reticuli, which is a double star (binary) system in our galaxy. It is not a galaxy of it\'s own. Galaxies have hundreds of millions to tens of billions of stars. So a two-star system doesn\'t qualify as a galaxy. Also, binary star systems are very common. Single stars, like our sun, are in the minority. Double stars, triple stars, quadruple star, etc. happen all the time. When star systems form, the massive systems generally form more than one star. When the system isn\'t massive enough to form multiple stars, solar systems form out of what\'s left over. So it is thought that lower mass stars, like our sun, will generally be found with solar systems (planets). In the more massive systems, those with multiple stars, any planets in solar systems are likely to be thrown out of the system by gravitational interaction with the stars of the system. So these would most likely not have planets except way out, past the orbits of the multiple star systems (in such systems the multiple stars orbit around each other).

Now as to how we know the age of our sun, that is rather simple actually. Scientist have extremely good models of stellar structure and stellar evolution. We can predict from first principles all of the different kinds of stars that we see in the sky. We know how massive they are, how hot they are, and how long they live before they turn into a supernova. Extensive observations of clusters of stars can see all of the different kind of stars and can see that the more massive stars have already turned off of the main sequence (this is when stars burn hydrogen in their cores) and have gone into the red-giant phase. This is exactly as predicted by our models and we can use this to date the age of globular clusters (large groupings of stars that have all formed at roughly same time). This precise agreement with theory gives great confidence that we know what is going on in stars. We can also look at the heavy elements produced in stars in their normal burning cycle and in the supernovae phase. This, too, agrees with theory and is another check that we have it right. So from all of this we know that our sun is roughly 5 billion years old. This also agrees well with our independent dating of the age of the earth at roughtly 4.5 billion years old. So this is yet another independent check that we understand the structure and evolutionn of stars. So in another 5 billion years our sun will also turn off the main sequence (it will have exhausted all the hydrogen in its core) and begin to expand and become a red-giant, engulfing the earth (our orbital distance will actually be inside the sun). However before that happens, in about 2-3 billion years, our galaxy, the Milky Way, will have collided with Andromeda, the other large galaxy in our local group of about 20 or so galaxies. This collision will probably knock the sun out of its orbit in our galaxy and strip away the earth and all the other planets. The collision will be extremely disruptive of the entire galaxy and destroy many, if not most, of the star systems. From observations, astronomers can see that this is a common occurance in the Universe. Galaxies collide all the time and it is an extremely violent event.

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Rick - really like the style and love the topic. Nothing like a poem about subatomic particles to get my juices flowing. This actually reminded me of a Rush lyric by Neil Peart for the song Natural Science (Permanent Waves, rel. 1980). For no particular reason, just in general flow of the rhythm and the deft but accessible scientific bent of the subject matter.

Posted 3 Months Ago