Explain twinkling of stars and draw diagram.

Asked by Jaymin24modi | 5th Nov, 2019, 05:32: PM

Expert Answer:

It can be observed that the apparent random wavering or flickering of objects seen through a turbulent stream
of hot air rising above a fire or a radiator. The air just above the fire becomes hotter than the air further up.
The hotter air is lighter (less dense) than the cooler air above it, and has a refractive index slightly less than that
of the coolerair. Since the physical conditions of the refracting medium (air) are not stationary,
the apparent position of the object, as seen through the hot air, fluctuates.  The twinkling of stars is a similar phenomenon.
 
The twinkling of a star is due to atmospheric refraction of starlight. The starlight, on entering the earth’s atmosphere,
undergoes refraction continuously before it reaches the earth. The atmospheric refraction occurs in a medium of gradually
changing refractive index. Since the atmosphere bends starlight towards the normal, the apparent position of the
star is slightly different from its actual position. The star appears slightly higher (above) than its actual position when
viewed near the horizon as illustrated in figure. Further, this apparent position of the star is not stationary,
but keeps on changing slightly, since the physical conditions of the earth’s atmosphere are not stationary,
as explained in previous paragraph.
 
Since the stars are very distant, they approximate point-sized sources of light. As the path of rays of light coming
from the star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering
the eye flickers – the star sometimes appears brighter, and at some other time, fainter, which is the twinkling effect.

Answered by Thiyagarajan K | 6th Nov, 2019, 08:29: AM