Astronomy Test (Chapter 11-14)
This diagram shows the life tracks from protostar to the main sequence for several stars of different masses. Which track represents the star that takes the longest amount of time to reach the main sequence?
1
This figure shows the life track of a one-solar-mass star from its beginnings in a collapsing cloud fragment until it becomes a main-sequence star. At which of the numbered points is the object generating energy primarily from gravitational contraction?
1,2, and 3
This figure shows the life track of a one-solar-mass star from its beginnings in a collapsing cloud fragment until it becomes a main-sequence star. At which of the numbered points is the object generating energy primarily from hydrogen fusion?
4 only
Study this H-R diagram. What is the spectral type of the star Sirius?
A
Both photos show the same field of view containing a star-forming molecular cloud. One of the photos was taken in visible light and the other in infrared light. Which one is the visible-light photo, and how do you know?
A is the visible-light photo, and we can tell because dust in the molecular cloud absorbs visible light, making the cloud appear dark.
Based on the curves shown here, which of the following statements best describes how we can distinguish a massive star supernova from a white dwarf supernova?
A white dwarf supernova is brighter at its peak and over a few months fades more steadily than a massive star supernova.
Study this H-R diagram. Which of the following stars is the largest in size (radius)?
Antares
Sirius, the brightest star in the night sky, is actually a binary star system: Sirius A is main-sequence star and Sirius B is a white dwarf. Nearly all the visible light we see from Sirius comes from Sirius A. But when we photograph the system with X-ray light, as shown here, Sirius B is the brighter of the two stars. Why?
As a white dwarf, Sirius B is much hotter than Sirius A and thus emits more X-rays.
Which of the following diagrams shows Earth and a neutron star correctly scaled?
BIG EARTH and tiny neutron star
Study this H-R diagram. Which of the following stars has (or had) the longest hydrogen burning lifetime?
Barnard's star
Study this H-R diagram. Which of the following stars is the most massive?
Beta Centauri
A binary system that looks like the one shown in this painting should shine brightly in X-rays. Which one of the four labeled regions is the source of most of the X-rays?
II
This star map shows stars as we see them in our sky from Earth, centered around the constellation Canis Major. Larger dots represent brighter stars, and a few of the brightest stars are identified. From this view alone, what can you conclude about Sirius?
It has the greatest apparent brightness of any star in this region of the sky.
What is this a picture of?
It is a painting of close binary star system in which the star on the right is a white dwarf surrounded by an accretion disk filled with gas drawn by gravity from the companion star on the left.
This photo shows gas associated with a protostar. What is this gas doing?
It is flowing outward in two opposite directions from the protostar.
What happens to the core of a high-mass star after it runs out of hydrogen?
It shrinks and heats up
Viewed from a distance, how would a flashing red light appear as it fell into a black hole?
Its flashes would shift to the infrared part of the spectrum.
What would happen to a neutron star with an accretion disk orbiting in a direction opposite to the neutron star's spin?
Its spin would slow down.
What is the main idea captured by this graph?
Low-mass stars are much more common than higher-mass stars.
This figure shows frames from a computer simulation of star formation, starting at the left with a large molecular cloud measuring more than a light-year across. What is happening as time passes (from left to right)?
The cloud is fragmenting into smaller pieces that will form stars
This painting shows an accretion disk around a black hole in a close binary star system. What physical law explains why matter flowing from the companion star orbits rapidly as it nears the black hole?
The law of conservation of angular momentum
The main photo and the smaller inset both show the same field of view containing a star-forming molecular cloud. One of the photos was taken in visible light and the other in infrared light. Which one is the infrared photo, and how do you know?
The main (larger) photo is the infrared one, which we can tell because molecular clouds emit much more infrared light than visible light.
This series of images shows the pulsar at the center of the Crab Nebula looking bright every 0.033 second. Based on these data and current theory of pulsars, what can we conclude?
The pulsar is a neutron star that makes one full rotation every 0.033 second
Why do some of the bright stars (such as the one indicated by the arrow) in this photo have cross-shaped spikes over them?
The spikes are an artifact of photography through a telescope.
Which of these stars has the greatest surface temperature?
a 30 MSun main-sequence star
This graph shows data collected by a gamma-ray telescope. What kind of event is it showing?
a gamma-ray burst from a distant galaxy
This photo shows an object located in the halo of our Milky Way galaxy. What kind of object is it?
a globular cluster of star
Which of these stars does not have fusion occurring in its core?
a red giant
The dark area stretching from the center of this picture to the upper right is about 50 light-years long and lies in the plane of the Milky Way Galaxy. What is it?
a star-forming cloud
What would you be most likely to find if you returned to the solar system in 10 billion years?
a white dwarf
Which of these binary systems is most likely to contain a black hole?
an X-ray binary containing an star and another object of equal mass
A brown dwarf is
an object not quite massive enough to be a star
What do we need to measure in order to determine a star's luminosity?
apparent brightness and distance
Sunspots appear darker than their surroundings because they
are cooler than their surroundings
This graph shows how the apparent brightness of an eclipsing binary system changes with time. Which of the four labeled regions represents the system at a time when one star is eclipsing the other?
both II and IV
What causes the cycle of solar activity?
changes in the organization of the Sun's magnetic field
This radio image shows emission from carbon monoxide molecules in the Milky Way; it spans a huge piece of the sky, nearly as large in angular extent as the Big Dipper. What are the bright regions in this image?
cool, molecular clouds
Express your answer using three significant figures.
d = 11.4 light−years
Procyon: parallax angle of 0.2860.
d = 3.50 pc
Express your answer using three significant figures. (1.35)
d =4.39 (light−years)
Alpha Centauri: parallax angle 0.7420.
d= 1.35 (pc)
Where do gamma-ray bursts tend to come from?
extremely distant galaxies
At the center of the Sun, fusion converts hydrogen into
helium, energy, and neutrinos.
Which of the following represents the true shape of a black hole as you'd see it (or measure it) as you flew past it in a spaceship?
just the ball
Solar energy leaves the core of the Sun in the form of
photons
Which of these layers of the Sun is coolest?
photosphere
This photo shows an object located in the halo of our Milky Way galaxy. Notice the many bright red dots in the photograph. What are they?
red giant stars
A spacecraft is on a trajectory that happens to be taking it near a black hole. Which diagram shows how the spacecraft's orbit will be affected?
slight curve with ball in the middle
All the stars in this photo are at about the same distance from Earth (some 26,000 light-years away). Which stars in this picture are the largest in size (radius)?
the bright red stars
What two pieces of information would you need in order to measure the masses of stars in an eclipsing binary system?
the time between eclipses and the average distance between the stars
