The astronomer will take 0.086 hours to observe the radius of the black hole.
A black hole is a place in space where gravity pulls so hard that even light cannot escape.
The astronomer has calculated the radius of a black hole to be 51.0 au by observing its period of variability in brightness.
'au' is the abbreviation for astronomical unit which is a unit of length used to measure the distance from Earth to sun.
1 au = 93 million kilometers
Also the radius is calculated on the variability in brightness, i.e. speed of light can be considered
Speed of light = 3 * [tex]10^{8}[/tex] m/s
So according to the formula of speed, time can be calculated as
time = distance / speed
time = 93 * [tex]10^{9}[/tex] / 3 * [tex]10^{8}[/tex]
time = 310 seconds
1 second = 0.0002 hour
310 seconds = 0.086 hour
The astronomer observed for 0.086 hours.
To know more about black hole,
https://brainly.com/question/27198295
#SPJ4
