How does the density of the lowest-density regions of the ISM compare to the density of air we inhale?
Answer
ISM density is far lower than the best vacuum achievable on Earth
The Interstellar Medium is characterized by extreme rarefaction, making its density far lower than even the most advanced vacuums created in terrestrial laboratories. For instance, the air inhaled by a person contains approximately $10^{19}$ molecules per cubic centimeter. In contrast, the lowest-density regions of the ISM exhibit a density of only about $0.1$ atoms per cubic centimeter. This vast difference highlights how empty the majority of interstellar space truly is, although the total mass accumulated over galactic volumes remains substantial.
Related Questions
What percentage of the Interstellar Medium’s total mass is attributed to solid dust grains?What two light elements account for approximately 98% of the total mass within the ISM gas component?What is the hottest major phase of the ISM, reaching temperatures between $10^6$ and $10^7$ Kelvin?What percentage of the total interstellar gas mass is concentrated within dense structures known as Molecular Clouds ($ ext{H}_2$)?Why do Reflection Nebulae, composed of dust surrounding a star, characteristically appear vividly blue?Which specific emission line is primarily used by astronomers to detect the presence of neutral atomic hydrogen ($ ext{HI}$)?How does the density of the lowest-density regions of the ISM compare to the density of air we inhale?What vital protective function does the dust component of the ISM provide within molecular clouds?What is the term used for the phenomenon where interstellar dust dims a star's apparent brightness due to wavelength-dependent scattering?Which European Space Agency mission has advanced the 3D mapping of extinction and measured Diffuse Interstellar Bands (DIBs)?