Question

Astronomy question.

Which star is coolest?

a. M8 V

b. K1 I

c. A7 III

d. B3 V

Answer 1

Answer: Following table is representing the different types of stars along with their temperature.

Type of star	Temp. in Kelvin
O	25,000-40,000
B	11,000-20,000
A	7,500-11,000
F	6,000-7,500
G	5,000-6,000
K	3,700–5,200
M	2,400–3,700

So, if we see the above table, it is clearly evident that the “M” type of stars has the lowest temperature therefore those stars will be the coolest stars. therefore option "a" seems to be correct. For more clarity i have also written the near figures of exact temperature of given stars which are as follows:

Exact temperature of given stars is as follows:

M8 V = Main sequence star =  2700 K

K1 I = Supergiants =  4700 K

A7 III = Giants 7900 K

B3 V =  Main sequence star = 17,600 K

From above figures also, i can say that M8V star has lowest temperature therefore its is coolest one. This implies that option "a" is correct.