Summary of results:
Maria Mitchell's score on this quiz was 20% (any incorrect choices are highlighted in red).
#1. If we plot the apparent brightness of Main Sequence stars (how bright they appear when viewed from Earth) against their stellar types, we find .
#2. If a Main Sequence star is ten times brighter than the Sun, we know that it is the Sun.
#3. A white dwarf formed from a recently collapsed giant is likely to have a temperature that of the Sun.
#4. Which stars on the Main Sequence today will become white dwarfs when they die?
#5. If a planetary nebula gas shell expands outward at a rate of thirty-two kilometers per second, how long does it takes to cover a distance of one A.U., in units of days?
Elapsed Time: 13.33 minutes
#1.
If we plot the apparent brightness of Main Sequence stars (how bright they appear when viewed from Earth) against their stellar types, we find .| the brightest stars have the earliest stellar types (O and B) |
| the brightest stars have the latest stellar types (M, L, and T) |
| the faintest stars have the earliest stellar types (O and B) |
| the faintest stars have the latest stellar types (M, L, and T) |
| no relation |
The apparent brightness of a star depends upon how far it lies from Earth (the further away a star is, the fainter it appears to us). The stellar types of the stars, however, are the same for a nearby star and a similar star on the other side of the galaxy. Because of this, there is no relationship between apparent brightness and stellar type.
#2.
If a Main Sequence star is ten times brighter than the Sun, we know that it is the Sun.| cooler than | the same temperature as |
| hotter than | smaller than |
The Main Sequence extends from faint, cool stars in the lower right-hand corner to bright, hot stars in the upper left-hand corner. As stars increase in temperature, they become brighter as well. A Main Sequence star ten times brighter than the Sun will not be much larger, and thus will be hotter as well.
#3.
A white dwarf formed from a recently collapsed giant is likely to have a temperature that of the Sun.| five times smaller than | similar to |
| five times greater than | fifty times greater than |
White dwarfs are typically five times hotter than the Sun when they form. With no nuclear fuel left to burn, they cool (and fade) slowly over time.
#4.
Which stars on the Main Sequence today will become white dwarfs when they die?| Stars with less than ten solar masses. |
| Stars with ten to 30 solar masses. |
| Stars with more than 30 solar masses. |
| We need more information to answer this question. |
Low mass stars become white dwarfs, because their self-gravity is not large enough to compress them into a more compact object such as a neutron star or a black hole.
#5.
If a planetary nebula gas shell expands outward at a rate of thirty-two kilometers per second, how long does it takes to cover a distance of one A.U., in units of days? Recall that an A.U. is equal to 1.5 × 10
kilometers (the distance between the Sun and the Earth).
Write your answer in the box, using a standard format for numbers. For example, if your answer is one-third of a day type "0.33" or "3.3e-1"; if your answer is three days type "3" or "3e0".
If velocity is equal to distance traveled over time (V = D/T), then travel time is equal to distance over velocity (T = D/V).
The expanding gas shell travels one A.U., or 1.5 × 10 kilometers, at a rate of 32 kilometers per second.
Its travel time is thus 1.5 × 10
kilometers / 32 kilometers per second, or 4.7 ×
10
seconds.
If there are 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a
day, then there are 60 × 60 × 24 = 86,400 seconds in a day.
Our travel times thus becomes 4.7 ×
10 seconds / 86,400 seconds per day, or 54 days.
The gas shells thrown off by a planetary nebula thus expand quickly through the surrounding star system, and then through its immediate surroundings.