Is a star that is orbiting a black hole emitting different spectra respectively while close and far from the black hole? Also is that star light, when reaching our eyes, some kind of delayed while the star moves from the outer part of the orbit to the inner part due to increased gravitational redshift and time dilation?
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asked Aug 11, 2021 at 16:50
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2 Answers
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There will be both special relativity and general relativity corrections. A special relativistic Doppler shift due to the velocity of the star relative to the observer's rest frame, and a general relativistic gravitational redshift.
You don't have to be around a black hole to notice these effects! Our GPS satellites have to account for effects like these.
See here:
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If viewed from the plane of the orbit, a star in a smaller orbit wold be moving faster and show more of a Doppler shift. Viewed from any angle, a star closer in would show more of a time dilation red shift.
