Consider a density fluctuation around the era of recombination when the universe had a temperature of 3000 K. If the density fluctuation is about 10 ly across, will the matter within that fluctuation begin clumping together?
A)The Jeans length for these numbers is about 100 ly. Matter will not begin clumping together because there is not enough mass in the fluctuation of 10 ly to overcome the gas pressure.
B)The Jeans length for these numbers is about 100 ly. Matter will begin clumping together since this is within the Jeans limit.
C)The Jeans length for these numbers is about 1 ly. Matter will not begin clumping together because there is not enough mass in the fluctuation to overcome the gas pressure.
D)The Jeans length for these numbers is about 1 ly. Matter will begin clumping together since this is within the Jeans limit.

Question

Quizplus · Accepted Answer

The critical wavelength for a density fluctuation to begin collapsing is determined by the Jeans length, which depends on the temperature and density of the gas. For a temperature of 3000 K, the Jeans length is about 100 ly. A density fluctuation of only 10 ly across does not contain enough mass to overcome the gas pressure and begin collapsing, so matter will not begin clumping together.

Consider a Density Fluctuation Around the Era of Recombination When