White dwarfs are dense, hot, inert cores of low-mass stars made primarily of the element carbon, which requires a temperature of to begin fusion. low-mass stars like the sun do not have enough mass to reach such a high temperature.

It needs a temperature of a 600 Million K to start a fusion. First generation stars were very massive (>30 M) because they were born in warmish clouds (100k) that required higher density for gravity to overcome thermal pressure. If the white dwarf the radius gets smaller.

 

 

I'm pretty sure there's a geometry rule for   anyways, if the triangle is equilateral, and the circle is circumscribed, the circle is outside of the triangle.  to find the area, you need the radius.  the radius should be a straight line from the center of the triangle to any of it's points.  draw lines from the center of the circle to each of the triangle points.  draw three more lines from the center to the middle of the sides of the triangle.  you should now have six separate 30-60-90 triangles inside of your original triangle. use your 30-60-90 rules to solve for the radius, then the circumference. 

Answer(a); // soil salinization and waterlogging;