Name: Niall C McCann
Status: Other
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
Someone told me that if you see an object in the sky which does not twinkle,
it is probably a planet. If this is the case, why do stars twinkle? I have
always noticed this star near the horizon in the winter in Ireland, and it
shifts slowly through the visible spectrum. Is this due to the Earth's
atmosphere/electromagnetic fields, or by gaseous clouds between Earth and
the star?
Replies:
I suspect that bright, color-changing star is Sirius, the dog star. It is
the brightest star visible from the Northern Hemisphere and is famous for
appearing as different colors. I believe the color changes are due to the
Earth's atmosphere (refraction effect).
It is the Earth's atmosphere that makes stars twinkle because they are so
distant that they appear as point sources of light that are displaced by
variations in our atmosphere. Planets do not twinkle being much closer,
they are not point sources.
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