Answer:
Explanation:
The star is revolving the black hole like earth revolves around the sun .so time period of rotation T is given by the following relation
T² =
, R is distance between black hole and star , M is mass of black hole
Given T = 4.8 hours
4.8² = 
Using the same equation for earth sun system
24² =
, Ms is mass of the sun and 50R is distance between the sun and the earth .
Dividing the equation
= 
= 2x 10⁻⁴
Answer:
Pluto.
Explanation:
an observary in Flagstaff, Arizona, discorvered it.
To solve this problem it is necessary to apply the concepts related to Gibbs free energy and spontaneity
At constant temperature and pressure, the change in Gibbs free energy is defined as

Where,
H = Entalpy
T = Temperature
S = Entropy
When the temperature is less than that number it is negative meaning it is a spontaneous reaction.
is also always 0 when using single element reactions. In numerical that implies 
At the equation then,






}
Therefore the temperature changes the reaction from non-spontaneous to spontaneous is 600.89K