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Intro Astronomy > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

Apparent magnitude is a measure of

A
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2
Q

A star of apparent magnitude +5 appears

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2
Q

A star of apparent magnitude -1 appears

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3
Q

Absolute magnitude (M) is defined as the apparent magnitude (m) a star would have if

A
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4
Q

Light leaving a point source spreads out so that the apparent brightness I of light per unit area varies with distance d according to which of the following laws (~ means “proportional to”)?

A
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5
Q

Spectral types of stars (e.g., B, K, G, F, etc.) define uniquely their

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6
Q

The Sun’s spectral classification in terms of surface temperature, as determined from absorption lines in its spectrum, is

A

G2V

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7
Q

What are the two physical parameters of stars that are plotted in the Hertzsprung-Russell diagram?

A

Luminosity and spectral type (or “surface” temperature)

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8
Q

What fraction of the stars surrounding our Sun are main-sequence stars?

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9
Q

The chemical makeup of the Sun’s surface can be determined

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10
Q

Compared to a star in the middle of the Hertzsprung-Russell diagram, a star in the upper right part of the diagram is

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11
Q

The space between stars is known to contain

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12
Q

The luminosity class of a star (I, II, III, IV, or V) is most closely related to which physical characteristic of the star?

A

Radius of the star

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13
Q

What is a star’s luminosity?

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14
Q

The Sun’s luminosity (energy emitted per second) is 3.83 × 1026 watts. What shorthand astronomical notion used to denote stellar Luminosity across the universe?

A

Lo

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15
Q

The classification of spectral types orders them from the Hottest to the Coldest stars in the universe. What is the order of stellar surface temperatures using this scale?

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16
Q

What is the name given to the space, in our Galaxy, that exits between the billions of stars?

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17
Q

How have complex molecules such as formaldehyde (H2CO) been detected in molecular interstellar clouds?

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18
Q

Which of the following common molecules found in interstellar space contains nitrogen atoms but no oxygen?
Group of answer choices

A

Ammonia (NH3)

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19
Q

What is the most abundant element in the universe?

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20
Q

Which of the following molecules is likely to be the most common in interstellar space?

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21
Q

What is the typical mass of a giant molecular cloud?

A

100,000 to 1 million solar masses

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22
Q

New stars are formed from

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23
Q

What major physical process is taking place inside stars that are on the main sequence in the Hertzsprung-Russell diagram?
Group of answer choices

A

Hydrogen is being converted to helium in their cores.

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24
Q

Thermonuclear reactions convert hydrogen into helium in the core of a star during which phase of a star’s life?

A

The main-sequence phase

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24
Q

How is gas distributed in interstellar space?

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25
Q

How do massive stars normally end their lives?

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26
Q

A white dwarf star, the surviving core of a low-mass star toward the end of its life, can be found on the Hertzsprung-Russell diagram

A
27
Q

What is the most important property of a star that governs its lifetime?

A

The mass of the star

28
Q

The absolute magnitude (M) of a star is the brightness the star would appear to have if it were placed at what distance from the Earth?

A
29
Q

How will our G2V star end its life?

A

Our G2V star will stop thermonuclear fusion in its core, expand to a Red Giant class star, which will engulf and vaporize our entire solar system, in about 5 billion years. Then it will collapse to a hot, white dwarf about the size of planet Earth.

30
Q

The Crab Nebula is a nearby example of what type of physical phenomenon?

A
31
Q

The most likely places where stars and planetary systems are forming in the universe are

A

in nebulae composed of gas, atomic and molecular, and dust.

32
Q

If you could travel in a spaceship flying 50,000mph, how many years would it take for you to travel to our Sun’s nearest star neighbor Proxima Centauri?

A

57,077 years to reach the next nearest stellar object.

33
Q

Accretion of matter within an interstellar cloud leads to

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34
Q

How far away are we from the nearest spectral-class V type star in our own Milky Way Galaxy?

A

9.3 x 107 miles

35
Q

New stars are formed from

A

huge, cool dust and gas clouds.

36
Q

Compared to a star in the middle of the Hertzsprung-Russell diagram, a star in the upper right part of the diagram is
Group of answer choices

A
37
Q

A white dwarf is

A
38
Q

Where are emission nebulae (H II regions) found?

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39
Q

How fast is the speed of light?

A

Light waves (all EM Radiation) travel at 186,000mi./sec. in every direction.

40
Q

When a typical nova explodes, it brightens in a few hours by a factor of

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41
Q

When any star on the main sequence was a protostar, it was

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42
Q

The spectral class of the star Enif is K2, while that of our Sun is G2. Which of the following conclusions can be drawn about Enif from this information?

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43
Q

One of the most recent supernova explosion known to have occurred in our own Galaxy

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44
Q

The Orion Nebula is

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45
Q

What point defines the end of the pre–main-sequence phase of a star’s life and the start of the main-sequence phase?

A
46
Q

Is the Earth, a stellar body, a self-luminous object?

A

No

47
Q

What is the lowest mass that an object can have and still be a star?

A
48
Q

Protostars are difficult to observe because

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49
Q

The lower edge of the Main Sequence band is known as ____ and represents the location in the HR-diagram at which stars begin their lives as main sequence stars.
Group of answer choices

A

the zero-age main sequence

50
Q

The diagram below is an HR diagram. The line indicates the location of the main sequence. Which of the five labeled locations on the HR diagram indicates a luminosity and temperature similar to that of a T Tauri star?

A

4

51
Q

Which of the following is NOT evidence of the existence of an interstellar medium?

A

molecular absorption lines in the spectra of cool stars

52
Q

Interstellar gas clouds may collapse to form stars if they

A
53
Q

Molecular clouds can be observed

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54
Q

Due to the dust in the interstellar medium, a distant star will appear to an observer on Earth to be

A
55
Q

As a main sequence star exhausts hydrogen in its core, its surface becomes___ and its energy output per second (luminosity) becomes ____

A
56
Q

The lowest mass object that can initiate thermonuclear fusion of hydrogen has a mass of about

A
57
Q

As a main sequence star exhausts hydrogen in its core, it next becomes

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57
Q

The Crab nebula is

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58
Q

Star clusters are important to our study of stars because

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they give us a method to test the our theories and models of stellar evolution.

59
Q

A planetary nebula is

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60
Q

A planetary nebula is

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61
Q

A white dwarf is composed of

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62
Q

A planetary nebula

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Intro Astronomy (4 decks)

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