Chp 15 mastering astronomy – Flashcards
Unlock all answers in this set
Unlock answersquestion
What do we call the bright, sphere-shaped region of stars that occupies the central few thousand light-years of the Milky Way Galaxy?
answer
the galaxy's bulge
question
The Sun's location in the Milky Way Galaxy is _________.
answer
in the galactic disk, roughly halfway between the center and the outer edge of the disk
question
What do we mean by the interstellar medium?
answer
the gas and dust that lies in between the stars in the Milky Way galaxy
question
What are the Magellanic Clouds?
answer
two small galaxies that orbit the Milky Way Galaxy
question
How do disk stars orbit the center of the galaxy?
answer
They all orbit in roughly the same plane and in the same direction.
question
How do we know the total mass of the Milky Way Galaxy that is contained within the Sun's orbital path?
answer
by applying Newton's version of Kepler's third law (or the equivalent orbital velocity formula) to the Sun's orbit around the center of the Galaxy
question
Fill in the blank: Elements heavier than hydrogen and helium constitute about _________ of the mass of the Milky Way's interstellar medium.
answer
2%
question
What do we mean by the star-gas-star cycle?
answer
It is the continuous recycling of gas in the galactic disk between stars and the interstellar medium.
This cycle is critically important to our existence, because it explains how the elements manufactured in past generations of stars — which are the elements of which we and our planet are made — came to be incorporated into star systems that formed later, including our own solar system.
question
What are cosmic rays?
answer
subatomic particles that travel close the speed of light
question
The primary way that we observe the atomic hydrogen that makes up most of the interstellar gas in the Milky Way is with _________.
answer
radio telescopes observing at a wavelength of 21 centimeters
question
Which of the following molecules is the most abundant in molecular clouds?
answer
H2
question
Interstellar dust consists mostly of _________.
answer
microscopic particles of carbon and silicon
These tiny, solid particles are very important, even though their total mass makes up less than 1% of the interstellar medium
question
Which of the following models best explains why our galaxy has spiral arms?
answer
The spiral arms are a wave of star formation caused by wave of density propagating outward through the disk of the galaxy.
question
What do we mean by a protogalactic cloud?
answer
a cloud of hydrogen and helium that contracts to become a galaxy
question
Most stars in the Milky Way's halo are _________.
answer
very old
There is no recycling of gas in the halo, so halo stars are quite old.
question
What is an ionization nebula?
answer
a colorful cloud of gas that glows because it is heated by light from nearby hot stars
question
What do halo stars do differently from disk stars?
answer
They orbit the galactic center with many different inclinations, while disk stars all orbit in nearly the same plane.
Actually, their speeds are the same or higher than those of disk stars, which is in part why we conclude that the halo contains vast amounts of dark matter.
question
Where does most star formation occur in the Milky Way Galaxy?
answer
in the spiral arms
question
Based on observations, which of the following statements about stars in the Milky Way is generally true?
answer
The older the star, the lower its abundance of heavy elements
question
What kind of object do we think lies in the center of the Milky Way Galaxy?
answer
a black hole of about 4 million solar masses
