Forgive me for posing this question, but I am a new student to the science of astronomy, and I am researching a question from my college professor. Can anyone tell me where I might find information concerning how to compare other G2 stars with the Sun? I have to answer the question: "Imagine that astronomers discovered a G2 star similar to the sun except that it showed very little rotation. In what ways might this star be similar to the sun and in what ways might it be different."I have searched the Internet for clues to finding the answer to this question, but have been unsuccessful so far. If anyone could point me in the right direction I would be grateful! Thanx!

Dave

For a star to be similar to our sun, the following would have to be very close. Radius, absolute magnitude, spectrum and position on the Hertzsprung-Russell diagram.

If a star had very little rotation, then it probably is the result of a close encounter with a more massive star, most likely when it emerged from the nebula were it was formed.

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FWIW - I would consider a rotation period of ~28 days (Sol) to be "very little rotation"!

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I was under the impression that the rotation rate of a star is one of the criterion used to determine -- very roughly, mind you -- the age of a star. Slower is older, faster is younger, that sort of thing.

...John...

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If the star is more or less identical to the Sun apart from rotation, then perhaps it has got a larger Oort cloud; most of the angular momentum in our solar system is in the planets and particularly in the Oort cloud.

A system with a larger or perhaps a more rapidly rotating system of planets and Oort cloud would probably have a slower rotation.

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I vaguely remeber it being claimed somewhere that the main reason our Sun has lost so much angular momentum is thought to involve its magnetic field. As charged particles are emitted by the Sun (the Solar Wind), they are deflected by the Sun's magnetic field, and thus they carry away some of its angular momentum. A Sunlike star with even less rotation might be simply older than the Sun (as John M. Dollan suggests), or it might have a stronger magnetic field.

Don't ask me what implications the latter might have for life as we know it, though?

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Most of the angular momentum of our solar system is in the planets. If this new star had a lower rotation rate, then it would hvae even less angular momentum than our sun. This would suggest that more of it was in that sun's planets, which would imply that they had greater mass. We would expect to see more gas giant planets in this star, with fewer terrestrial (meaning earth-like) planets. Although this star would have the same intensity and color as our star, it's planets might not be a good place to look for a place to live.

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I would expect it would have a substantially less powerful magnetic field. It is thought the sun's magnetic field is due to a dynamo effect:

http://science.msfc.nasa.gov/ssl/pad/solar/dynamo.htm

There would also be minimal differential rotation, which plays a major part in solar activity. I would *guess* there would be much less activity with a slowly rotating star. In any event, it would be different. The sunspot cycle would be different (assuming there were many sunspots), sunspot rotation would be different.

The star would be less oblate, of course.

http://www.noao.edu/noao/noaonews/dec97/node2.html

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