A giant molecular cloud is 30 pc in diameter and has a density of 330 hydrogen molecules/cm^3. What is it's mass in units of solar masses? (Notes: the volume of a sphere is 4/3pieR^3 , and the mass of a hydrogen atom is 1.67 x 10^-27 kg. A hydrogen molecule consists of 2 H atoms.)

If a giant molecular cloud is 38 pc in diameter and a shock wave can sweep through it in 6 million years, how fast is the shock wave going in kilometers per second? (Notes: 1 pc = 3.1  1013 km; 1 yr = 3.2  107 s.) answer in km/s

A) A typical dust grain has a radius of about 0.1 micrometers and a mass of  10-14   grams. Roughly how many dust particles are in a cloud containing 1000 Msun of dusty gas if 1% of the cloud's mass is in the form of dust grains?  B) What surface area would be covered by these grains if you put them side by side? Assume these grains are spherical. Answer in square light-years. C) Estimate the total surface area covered by the cloud assuming it's matter density is like that of a typical molecular cloud, about 10-21 g/cm3 (Hint: first calculate the clouds volume from it's mass and density, then determine its radius using the formula for volume of a sphere) Answer in square light-years.  D) Comparing all above answers, What are the chances (very roughly) that a photon passing through the cloud will hit a dust grain?

why do dark streaks appear in visible light images of the Trifid nebula, but appear bright in an infared image

if a protostellar disk is 260 au in radius and the disk plus the forming star together contain 7 solar masses what is the orbital speed at the outer edge of the disk in km per second. use the circular orbital velocity formula

T/ F  The distance unit best for interstellar distances is the light-year. ___   The distance unit best for intergalactic distances is the mega-parsec. ___

How many years? Thank you!

If a giant molecular cloud has a diameter of 56 pc and drifts relative to nearby objects at 19 km/s, how long (in yr) does it take to travel a distance equal to its own diameter?

If a giant molecular cloud is 60 pc in diameter and a shock wave sweeps through at 25 km/s, how long will it take the shock wave (in years) to sweep through the cloud?