Final answer:
If a star 65 light-years away ceased emitting light, it would take 65 years for us to detect this because light travels at a fixed speed, delivering information from across the cosmos to Earth. The 'now' for astronomers is tied to the arrival of light, so the soonest one can know about changes in a star is after the light has had the time to traverse the intervening distance.
Step-by-step explanation:
If a star located 65 light-years away from Earth stops giving off light energy at this very moment, we would not know about this event until 65 years later. This is because light takes one year to travel a distance of one light-year by definition, and thus the information of the star's status travels at the speed of light to reach us. The answer is A) 65 years.
According to the principles of physics, there is an unavoidable delay in obtaining information from distant objects in space, such as stars. Hence, in case of the Sun, which is 1.50×10¹¹ meters away from Earth, it would take approximately 8 minutes for us to become aware if it 'turned off', since that’s how long sunlight takes to reach us.
For astronomical observations, the concept of 'now' is inherently based on when light from a celestial body reaches Earth, so we can only perceive events as they were when the light left the source, not as they are in the present moment.