What Would We See if the Sun Suddenly Darkened?

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SUMMARY

If the Sun's surface instantaneously darkened, observers on Earth would notice the change approximately 8 minutes later, as this is the time it takes for light from the Sun to reach Earth. The discussion emphasizes that significant changes in brightness cannot occur on time scales shorter than the light travel time across the object. Additionally, the concept of redshift is introduced, but it is noted that calculating redshift in this scenario is not feasible due to the nature of the event. The geometry of the Sun as a sphere also plays a role in understanding the observation delay.

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  • Understanding of light travel time and its implications in astrophysics
  • Familiarity with the concept of redshift and its calculation
  • Basic knowledge of Hubble's constant and its relevance to cosmic distances
  • Comprehension of spherical geometry in relation to astronomical observations
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  • Study the calculation and significance of redshift in cosmology
  • Explore Hubble's Law and its applications in measuring cosmic distances
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Homework Statement


Explain, as quantitatively as you can, what would be observed from Earth if the Sun's surface instantaneously darkened and hence explain why the brightness of a body cannot significantly alter on time scales significantly less than the light travel time across it.


Homework Equations



Hubble's constant = H
velocity of galaxy = v
distance from Earth = d
d = v / H

redshift = z
speed of light = c
z = v / c

The Attempt at a Solution



The first thing that came to my mind is that it will take ~ 8 minutes for the photons to reach the Earth, meaning that any observation from the Earth would be 8 min after the event. The Sun is still receding from the Earth. However, we will not be able to calculate the redshift.

Am I nowhere near what they are looking for in the answer?

thanks x
 
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Think about the fact that the Sun is a sphere (almost!), and that the centre of the visible sphere is nearer to you than the edge.
 

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