Astronomy 122 - Exam 3 answers



1.	Why does the H-R diagram of a globular cluster NOT contain any stars with high 
	luminosity and high temperature on the main sequence?

		b.	these high-mass stars have evolved away from the main sequence

2. 	What is a stellar association?

		b.	loosely bound group of newborn stars

3.	Approximately what temperature is required in a collapsing protostar to 
	ignite nuclear burning?
	
		d.	10,000,000 K

4.	What do many astronomers regard as a triggering mechanism for star formation?

		a.	passage of a shock wave

5.	What is unusual about the Algol binary?

		a.	The most massive of the two stars is still on the main sequence

6.	The Sun will never be

		b.	a neutron star

7.	Most of the supernovae seen by astronomers are

		d.	in other galaxies

8.	Newborn star clusters are often found with

		a.	emission nebulae

9.	Which development within the deep interior of the Sun will eventually 
	lead to major changes?	

		d.	the build-up of helium in the core

10. 	How does a medium mass star evolve, on the H-R diagram, at the end of 
	its main sequence lifetime?

		c.	to higher luminosity and lower surface temperature

11.	Infrared stars within the Orion Nebula are examples of which stage of 
	stellar evolution?

		b.	protostar and young star 

12.	The most likely site for the manufacture of heavy elements (beyond hydrogen 
	and helium) in the Universe is

		c.	in the deep interiors of stars

13. 	Which class of stars is the oldest?

		c.	stars with less abundance of heavy elements

14. 	A pulsar is composed mostly of

		d.	neutrons

15.	Which of the following processes requires the highest temperature to proceed?

		b.  	Carbon fusion

16.	A star that emits a planetary nebula is likely to

		a.	become a white dwarf

17.	The speed of a neutrino is close to

		d.	The speed of light

18.	Which of the following would be a reasonable age for a red giant star 
	in the sky today?
	
		c.	10,000,000,000 years

19.	The path drawn on the H-R diagram below represents the change in

		b.	a Sun-like star during the “birth” of the star

 

20.	Where is one most likely to find a white dwarf star?

		a.	Within a globular cluster

21.	The pre main-sequence path on the H-R diagram of a protostar depends on

		c.	its mass

22.	During the formation of stars, the collapse of globules heats the 
	interstellar gas

		c.	from less than a hundred degrees Kelvin to millions

23.	The heaviest stars are formed by collapsing clouds
	
		b.	faster than the lightest stars

24.	Stars of about twice the mass of the Sun are formed from the collapse 
	of interstellar clouds in

		c.	about 10,000,000 years

25.	OB associations are marked by

		d.	new star formation

26.	Which of the following objects is smallest?

		c.	neutron star

27.	ZAMS stands for

		b.	zero-age main sequence

28.	A brown dwarf is

		a.	a failed star

29.	When is hydrostatic equilibrium established in a solar mass star?

		c.	when the core of the star reaches 10,000,000 K

30.	A chain-reaction of star formation can be propagated by

		a.	supernovae explosions

31.	The energy for the initial increase in the temperature of a collapsing cloud 
	in star formation comes from

		d.	gravitational energy

32.	The heavy elements you are made of were formed in

		b.	a supernova explosion

33.	Which of the following statements is false?

		d.	supernovae occur only in binary star systems. 

34.	The expected aging of two stars in a binary system would normally be

		a.	the most massive star would evolve quickest

35.	Stars which contribute most to the chemical enrichment of the interstellar medium 
	are stars which are

		c.	more massive than the Sun

36.	At about what temperature will helium begin to fuse into carbon

		c.	100,000,000 K

37.	The neutrino is

		a. 	an elusive, subatomic particle, having very little mass, 
			and difficult to detect

38.	The age of a cluster of stars can be judged by

		a.	the turnoff point on the main sequence of its H-R diagram

39.	Why are instruments that study ultraviolet radiation put into space orbits?

		a.	The Earth’s atmosphere absorbs ultraviolet radiation.

40.	How does a typical nova explosion compare with that for a supernova?

		a.	novas almost always occur in binary stars.
		b.	novas involve explosions of the surface layers.
		c.	novas leave behind most of the mass of the star.
--->		d.	all of the above.
		e.	none of the above.

41.	Stellar remnants with masses between 1.4 and 3 solar masses will be

		b.	neutron stars

42.	A planetary nebula is 

		c.	ejected gases from a central star

43.	What is the main product of helium “burning” in red giant stars?

		a.	carbon nuclei

44.	A globular cluster is a group of stars

		c.	all very old, and with little of the heavy elements

45.	A very low mass object (0.01 to 0.08 solar mass) of low luminosity is

		d.	a brown dwarf

46.	Which physical phenomenon keeps a white dwarf star from collapsing?

		a.	electron degeneracy or “quantum crowding”

47.	In our galaxy, as time goes on, the abundance of metals

		a.	increases

48.	 A type II supernova is produced when:

		b.	the collapse of a star's iron nucleus causes a shock wave 
			that "blows off" the envelope of the star.

49.	A white-dwarf is the likely result from which type of the following 
	main-sequence stars?

		b.	K	

50.	What is the closest location for finding material formed in a supernova explosion?

		e. 	your own body

51.	A group of thousands of very old stars with very few heavy elements is

		a.	a globular cluster

52.	The mass of a neutron star

		d.	must be less than 3 solar masses

53.	The crab nebula is

		a.	the result of a supernova explosion

54.	Heavy elements which are mixed into the material from which new generations 
	of stars may be formed primarily come from

		c.	supernovae

55. 	Which of the following properties does the neutrino NOT possess?

		a.	extremely small mass
		b.	travels at the speed of light
-->		c.	electrical charge equal to that of the electron
		d.	very penetrating through any matter

56.	Type I supernovae occur in

		b.	binary star systems.

57.	Which of the following effective reactions is called the triple alpha process?
	
		c.	He + He + He  ->  C + energy

58.	Which of the following effective reactions is called the CNO cycle?
		
		a.	C + 4 H  ->  C + He + energy

59.	What fraction of the mass of a red giant is ejected as a planetary nebula?

		b.	substantial, between 0.25 and 0.6

60.	What method can provide direct information about the behavior of stars 
	beneath their surfaces?

		c.	neutrino astronomy

61. 	Helium flash refers to 

		d.	the runaway helium fusion in the core of a low mass red giant star

62. 	Where in the Universe would you look for a “protostar”?

		a.	in dense dust and gas clouds

63. 	Which of the following are NOT very young stars or pre-stellar objects

		a. 	infra-red emitting stars in gas and dust clouds
		b.	T Tauri stars
		c.	protostars
-->		d.	red giants

64.	How are elements with nuclei heavier than iron produced?

		b.	they are produced during supernova explosions

65. 	A T Tauri star is at what stage of its stellar evolution?

		b.	very early stages, just after protostar formation

66.	Most of the energy of a supernova explosion is carried away by

		b.	neutrinos.

67.	Stars are formed from interstellar matter.  Why then are stars in globular 
	clusters metal-poor, while stars in open clusters are metal-rich?

		a. 	because stellar evolution and supernova explosions increase 
			heavy metal concentrations steadily with time
		
68. 	A supernova explosion 

		a.	produces heavy nuclei all the way up to uranium and thorium.

69.	The mass limit of 1.4 solar masses is known as

		d.	the Chandrasekhar limit		

70.	Which of the following objects is likely to be the oldest?

		a.	globular cluster	

71.	The characteristics of red supergiant stars are

		d.	brightness of about 10,000 Suns and a diameter of about 
			Mars’ orbit

72.	What type of star did the Hubble Space Telescope find many examples of
	in the globular cluster M4?

		a.	white dwarfs

73. 	The one characteristic shared by all white dwarf stars without binary 
	companions is that

		b.	they have ceased to generate energy by thermonuclear processes 
			or gravitational contraction, and are cooling down

74.	Which type of Supernova would typically occur soonest after the birth of a star?

		b.	type II

75.	What surface surrounding a binary star system defines the boundaries of gravitational 
        influence of each star?

		a.	Roche Lobe

 



76.	On the diagram above, identify region A

		b.	red giant stars	

77.	Identify region B

		c.	blue giant stars

78.	Identify region C

		c.	the main sequence
		
79.	Identify region D

		c.	white dwarfs
		
80.	Identify region E

		d.	red dwarfs

81.	The Crab Nebula is

      		d.	a supernova remnant

82.	A white dwarf star is about the same size as 

		c.	the Earth

83.	By about how much does a star's luminosity increase during a typical supernova 
	explosion?

		e.	100,000,000

84.	The sun will eventually become

		d.	a white dwarf


86. 	How may Roche Lobes are there in a binary star system?

		Two		

87.	What is the name given to a star-like object that never burned hydrogen?

		Brown dwarf

88.	What type of star is Sirius B?

		White dwarf

89. 	In what year did that most recent supernova visible to the naked eye appear in 
	the sky?

		1987

90.	What fraction of the Sun’s mass is required for a collapsing system to form 
	a star?

		0.08 or 8%

91. 	In what astronomical body in the sky did SN1987A appear?

		Large Magellanic Cloud

92. 	What type of star is often found at the center of a planetary nebula?

		White dwarf

93.	There is a mass limit for a star in the white dwarf phase, the Chandrasekhar
	limit, beyond which the star can no longer support itself against its own weight.  	
        What is the value of this mass limit, in terms of solar mass?	

		1.4 Solar Masses