Based on what you know about observations of the interstellar medium at wavelengths other than for visible light, select all of the correct statements from the following list. -The 21-cm radio observations are of neutral hydrogen. -Much interstellar dust between stars is not visible. -The source of hot gas observed at X-ray wavelengths is not known. -All interstellar material is cool. -Interstellar dust is observed at ultraviolet wavelengths. -Giant molecular clouds consist mostly of CO molecules. -Material observed at wavelengths longer than that of visible light is usually cool.

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.

Which portion of the EM spectrum is best for understanding the giant Molecular Clouds from which stars are born? Far infrared GXUVIR a. FAR IR b. VISIBLE OC. NEAR IR Od. Molecular Clouds are not shown in any of them Oe. All show the clouds equally well Visible wwwwwwww GXUVR Near infrared. www GXUVIR

Planetary Nebula Age. Suppose a planetary nebula is 1 pc in radius. If the Doppler shifts in its spectrum show it is expanding at 20 km/s, how old is it? (Note that 1 pc equals 3.1x1013 km, and 1 year equals 3.2x107 seconds, to two significant figures.) Please round your answer to two significant digits. At = years

Match each statement with the appropriate item (if the first corresponds to B and the next 4 to C, enter BCCCC) 1) group of stars that was formed all at the same time, with the same composition 2) the top of the main sequence of a cluster; more massive stars in the cluster have already evolved 3) globular clusters stars that are burning helium in their core 4) young, spread out star cluster 5) old, dense star cluster A. main sequence turnoff B. open cluster C. star cluster D. horizontal branch stars E. globular cluster

Giant Density. If a star the size of the Sun expands to form a giant 20 times larger in radius, by what factor will its average density decrease?(Hint: The volume of a sphere is - Tr*.)

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

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!