At the average density of a star-forming molecular cloud, about 900 atoms per cm3, determine how large a sphere you would need to encompass mass equal to that of the Sun? Enter the radius of this sphere in light-years. (HINTS: 900 atoms per cm3 corresponds to a density of 1.51×10-18kg/m^3; the mass of the Sun is 2×1030kg) (The volume of a sphere is 4/3 * π * R3) (my previous answer of 6.812 X 1015 was incorrect)

If an open cluster contains 650 stars and is 27 pc in diameter, what is the average distance between the stars? (Hint: On average, what share of the volume of the cluster surrounds each star?)

If an open cluster contains 350   stars and is 48 pc in diameter, what is the average distance between the stars? On average what, share of the volume of the cluster surrounds each star?

Cluster Sizes. An open cluster is a collection of 10 to 1000 stars in a region about 25 pc in diameter. About how far apart are the stars in an open cluster in units of pc? (Hints: What share of the cluster's volume belongs to a single 4 Tr. Use the cited value for the maximum number of stars in your calculation.) star? The volume of a sphere is pc.

How is the blue color of a reflection nebula related to the blue color of the daytime sky?

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 supernova’s energy is often compared to the total energy output of the Sun over its lifetime. Using the Sun’s current luminosity, calculate the total solar energy output, assuming a 1010 year main-sequence lifetime. Using Einstein’s formula E=mc2 calculate the equivalent amount of mass, expressed in Earth masses. [Hint: The total energy output of the Sun over its lifetime is given by its current luminosity times the number of seconds in a year times its ten billion-year lifetime; ; mass of earth = 6×1024kg; c = 3×108m/s. Your answer should be 200-300 Earth masses.]

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?

What evidence can you cite that the interstellar medium contains both gas and dust? (Select all that apply.) (1)The dust of the interstellar medium can be detected from the emission lines of elements heavier than iron. (2)The dust of the interstellar medium can be detected by the extinction of light from distant stars. (3)The dust of the interstellar medium can be detected by the scattering of blue light from distant or embedded objects. (4)The gas of the interstellar medium can be detected from the radiation of ultraviolet photons. (5)The gas of the interstellar medium can be detected from the radiation of photons of wavelength 21 cm. (6)The gas of the interstellar medium can be detected from the absorption lines present in the light from distant stars, which must be caused by a medium of a density and temperature other than that of the stars emitting the light.

How many years? Thank you!