Student helps to discover new planet

1.	a) Which SI units would be used to measure the following quantities:
	i) Size	ii) Mass	 iii)	Temperature 	iv) Luminosity?
 	b) Find out the accepted values for the Sun.

2.	If the radius of the earth is 6.4 x 106m, calculate the approximate size of the 	new planet.

3.	a)What is the definition of a light year?
   	b) Calculate the approx distance of the new planet from the earth in km.
   	c) Why are astronomical distances usually measured in light years?