Question : 31.Stars born inA.reflection nebulae.B.dense molecular clouds.C.HII regions.D.the intercloud medium.E.the local : 1777239

31.Stars are born in
A.reflection nebulae.
B.dense molecular clouds.
C.HII regions.
D.the intercloud medium.
E.the local bubble.

32.Absorption lines due to interstellar gas
A.are wider than the lines from stars because the gas is hotter than most stars.
B.are more narrow than the lines from stars because the gas has a lower pressure than stars.
C.indicate that the interstellar medium contains dust.
D.indicate that the interstellar medium is expanding away from the sun.
E.none of the above

33.What is the lifetime of a 10 solar mass star on the main sequence?
A.3.2 ´ 10⁷ years
B.320 years
C.3.2 ´ 10¹² years
D.1 ´ 10⁹ years
E.1 ´ 10¹¹ years

34.What is the lifetime on the main sequence of a 2 solar mass star compared to the approximately 10 billion year life of our Sun? Pick the best answer.
A.1.8 ´ 10¹¹ years
B.1.8 ´ 10¹⁰ years
C.1.8 ´ 10⁹ years
D.1.8 ´ 10⁶ years
E.1.8 ´ 10³ years

35.If the dust around a protostar radiates most strongly at 30 microns or 30,000 nm, what is the approximate temperature of that dust? Hint: T in K =3,000,000/wavelength in nm.
A.100,000 K
B.10,000 K
C.1000 K
D.100 K
E.10 K

36.A jet has an angular length of 10 seconds of arc and flows from a star at a distance of 2,000 pc. How far does this jet extend away from the star?
A.20,000 pc
B.20,000 AU
C.20, 000 ly
D.20,000 miles
E.20,000 km

37.The H-R diagram of a young star cluster shows
A.that high mass stars have not yet reached the main sequence yet.
B.that low mass stars have not yet reached the main sequence yet.
C.mainly giant stars.
D.no stars since none have reached the main sequence yet.

38.As a star begin to form the initial energy source is from
A.nuclear fusion.
B.nuclear fission.
C.gravitational potential energy.
D.magnetic fields.

39.While on the main sequence a star's primary energy source comes from
A.nuclear fusion.
B.nuclear fission.
C.gravitational potential energy.
D.magnetic fields.

40.What must occur for an object to be considered a main sequence star?
A.Hydrostatic equilibrium
B.Nuclear fusion reaction in the core
C.Protostar life begins
D.Both a and b