Chapter Questions
The ring ejected by the supergiant star in Figure $11-1$ has a radius of about 7 seconds of arc. If the cluster is 20,000 ly from Earth, what is the radius of the ring in light-years?
If a giant molecular cloud is $50 \mathrm{pc}$ in diameter and a shock wave can sweep through it in 2 million years, how fast is the shock wave going in kilometers per second?
If a giant molecular cloud has a mass of $10^{35} \mathrm{kg}$, and it converts 1 percent of its mass into stars during a single encounter with a shock wave, how many stars can it make? Assume the stars each contain 1 solar mass.
If a protostellar disk is $200 \mathrm{AU}$ in radius, and the disk plus the forming star contain 2 solar masses, what is the orbital velocity at the outer edge of the disk in kilometers per second?
If a contracting protostar is five times the radius of the sun and has a temperature of only $2000 \mathrm{K}$, how luminous will it be? (Hint: See Chapter $9 .)$
The gas in a bipolar flow can travel as fast as $100 \mathrm{km} / \mathrm{s}$. If the length of the jet is 1 ly, how long does it take for a blob of gas to travel from the protostar to the end of the jet?
If a $T$ Tauri star is the same temperature as the sun but is ten times more luminous, what is its radius? (Hint: See Chapter $9 .)$
Circle all of the $^{1} \mathrm{H}$ and $^{4} \mathrm{He}$ nuclei in Figure $11-10$ and explain how the CNO cycle can be summarized by $4^{1} \mathrm{H} \rightarrow^{4} \mathrm{He}+$ energy.
How much energy is produced when the CNO cycle converts $1 \mathrm{kg}$ of mass into energy? Is your answer different if the mass is fused by the proton-proton chain?
If the Orion Nebula is 8 pc in diameter and has a density of about 600 hydrogen atoms/cm $^{3}$, what is its total mass? (Hint: The volume of a sphere is $\frac{4}{3} \pi R^{3}$.)
The hottest star in the Orion Nebula has a surface temperature of $40,000 \mathrm{K} .$ At what wavelength does it radiate the most energy? (Hint:See Chapter $7 .)$