Practice Exam 1 (ch13-16)

A star is observed to have an apparent brightness which is 104 times its absolute brightness. How far away is it?

1000 parsecs

Spectroscopic Parallax refers to

a method for Önding distances to stars

The idea that a supernova is preceded by a huge burst of neutrinos is

a prediction that has now been observed

Type II supernovas have the following properties:

a spectrum with hydrogen lines and a variable maximum brightness

The problem of stars îtwinklingî due to atmospheric turbulence

can be corrected by using a guide star

When a red giant star begins to burn helium, its diameter

decreases but not to its main sequence size.

Ham radio operators sometimes operate receivers for the 2 meter wavelength. The 2 meters refers to the

distance from one maximum of the radio waves to the next

Which of these answers describes the fundamental assumption that is behind all of the methods that astronomers refer to as the "distance ladder?"

distant object are similar to nearby objects

The core of a red supergiant star stops shrinking because its

electrons touch eachother

The point at which even an outwardly directed light ray is pulled into a black hole is called th

event horizon

Stars that are much more massive than our Sun

form faster and burn out faster

To see a large but faint object such as a nebula, you would need a telescope with large

light gathering power

On a HR diagram, a visible white dwarf star is in the

lower left corner

A star with an absolute magnitude of 5:7 and an apparent magnitude of 1:2 would appear in our sky as a star

of dazzling brightness

A hydrogen atom with its electron removed (a H+ ion in other words) is actually a

proton

A star that is cooler than most other stars will probably look

red

Our Sun is a type G2V star on the main sequence. As it ages and uses up its fuel we expect it to

remain a G2V star until it leaves the main sequence

The 'Little Green Men Standard Time" hypothesis for the repeating radio signals seen in 1968 was rejected partly because the repetition rate was

slowing down

Which of the following magnitudes corresponds to the brightest star?

0

The mass of a carbon atom is 12.00amu while the mass of a helium-4 atom is 4.003amu. If a gamma ray photon splits a carbon atom into three Helium atoms, how much energy is converted into mass?

0.009amu

A star is seen to move by 0:2 seconds of arc between February 1, 1999 and August 1, 1999 and then back to its starting point on February 1, 2000. What is the parallax angle for this star?

0:1 seconds of arc

The apparent brightness of our Sun is roughly 1000 watts per square meter. At a distance of 30 times the Earth-Sun distance, the apparent brightness of our Sun would be

1.1 watts per square meter

A star with a distance modulus of zero is at a distance of

10 parsecs

Our Sun is a G2V star with absolute magnitude 4:8. Suppose that a star of spectral type G2V is observed to have apparent magnitude 9:8. How far away is it?

100 parsecs

Suppose that the color and behavior of a star identify it as a type that we know has absolute magnitude ñ3. If the starís apparent magnitude is found to be 7, how far away is it?

1000 parsecs

A star whose apparent brightness is 1 100 that of a sixth magnitude star would have magnitude

11

Suppose that a áash of lightning from a cloud 2500 meters away is followed by a clap of thunder two seconds later. Assume that the light arrived in a negligible time and calculate the speed of the sound waves.

1250m/s

The velocity of sound waves is roughly the same for all wavelengths. Suppose that a sound wave has a wavelength of one meter and a frequency of 1000Hz. The wavelength of a 500Hz sound wave would then be

2 m

The star delta-Eridani shows a heliocentric stellar parallax of almost exactly 1/9 seconds of arc. The distance from our Sun to delta-Eridani is

9 parsecs

The star Wemadeit shows a stellar parallax angle of 0.3 seconds of arc while the star Waytoofar shows a stellar parallax angle of 0.4 seconds of arc. From this, you can conclude that

Waytoofar is closer to our Sun than Wemadeit

When an interstellar cloud fragment does not have enough mass to form a star powered by nuclear fusion, but gets hot enough to glow for a while, it is called

a brown dwarf

The Örst red giant stage of a one solar mass starís life usually ends with

an explosion in the helium core

The luminosity class of a star is

an indication of the broadening of its spectral lines

Because of the electrical repulsion between atomic nuclei, nuclear fusion happens only

at high temperatures

A star that forms an iron core most likely has a mass of

between 15 and 20 solar masses

High protostellar winds of ejected gas occur

between the initial contraction and the ignition of nuclear burning

To measure the heliocentric stellar parallax of a star, you mostly need a telescope wit

high resolving power

In the Hertzsprung-Russell Diagram, a main sequence star might be found

in the lower right or upper left

For stars on the main-sequence, stars with increasing mass have

increasing surface temperature and absolute brightness

Suppose that a star has a spectrum that includes red, blue, and violet lines spaced in the pattern of the lines from hydrogen but the red line is has a wavelength of 660 nm instead of the usual 656 nm. From this evidence, you can conclude that the star is

moving away from us

When a white dwarf star collects matter from a neighboring star, fusion reactions on the surface of the white dwarf cause

novas

A spectroscopic binary star system is one in which we see

spectral lines shifting back and forth

Think of the ëfrontíof a telescope as the end that light enters. A telescope with Newtonian Focus has the eyepiece

sticking out the side near the front

When the hydrogen fuel runs out at the center of a main sequence star, the star

swells up and becomes a red giant

The average energy of motion of an atom or molecule in a gas is called its

temperature

We can see the star Sirius and its companion, the Pup, moving around each other. Careful measurement of this motion can provide

the masses of both stars in the system

Because mirrors only use one surface, they have a big advantage over lenses: They can be

thinner and larger in diameter

In a Hertzsprung-Russell diagram, the surface temperature of stars increases going

to the left

A mirror that is shaped like a shallow bowl sitting on the table with its open end facing up will focus light that comes

vertically down from above