# Interstellar space: pressure, rms speed of the atoms

Interstellar space, far from any stars, is filled with a very low density of hydrogen atoms (H, not H_2). The number density is about 1 atom/cm^3 and the temperature is about 3K.

A & B) Estimate the pressure in interstellar space. Give your answer in Pa and in atm.

C) What is the rms speed of the atoms?

D) What is the edge length L of an LxLxL cube of gas with 1.0 J of thermal energy? Give your answer in meters.

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#### Solution Preview

A & B) Estimate the pressure in interstellar space. Give your answer in Pa and in atm.

p= 1/3 m n v^2

where m= mass of hydrogen atom= 1.66x10^-27 kg

or in scientific notation= 1.66E-27 Kg

n = 1 atom/cm^3= 1000000 atoms/m^3

v= rms speed= 273.5311 ...

#### Solution Summary

Estimates pressure in Interstellar space and the rms speed of the atoms in Interstellar space.