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-3 votes

How would a person know if a planet is orbiting a binary star?

You check the periodic frequency shift with the Doppler effect. The light from the two stars is not very suitable because each light source moves. Much better: The binary system (total mass $m_A\...
9herbert9's user avatar
1 vote

Did the late 2019 "fainting" of Betelgeuse show any spectral trends that differ from it's normal variability?

It's now nearly four years after "the great dimming of Betelgeuze" - and the matter has not yet been finally settled; as such this answer will necessarily include some personal judgement and ...
planetmaker's user avatar
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4 votes

Why is the H-alpha line slightly shorter in wavelength (656.28 nm) in air than in vacuum (656.46 nm)? Shouldn't it be longer?

This is not due to where the light is emitted, but where it is measured. When light enters a medium, such as air, it slows down. This is called refraction (and is the reason that prisms etc can bend ...
James K's user avatar
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