True, They contain old stars and posses little gas or dust
The suspended ash made for some some spectacular sunsets! Sulfuric acid was spread worldwide, increasing acidity of rain. Ash deflected energy from the sun, causing a slight drop on global temps for a few years.
To solve the problem it is necessary to use the concepts related to the calculation of periods by means of a spring constant.
We know that by Hooke's law

Where,
k = Spring constant
x = Displacement
Re-arrange to find k,




Perioricity in an elastic body is defined by

Where,
m = Mass
k = Spring constant


Therefore the period of the oscillations is 0.685s