unit 9
Who was the astronomer who is the "H" in H-R diagram?
Hertzsprung
The core of a massive star becomes a neutron star. What happens to the rest of the star's material?
It explodes outward as a supernova
Which of the following types of stars will spend the longest time (the greatest number of years) on the main sequence?
K
A visitor asks, "Will the Sun explode in a supernova?"
No, it doesn't have enough mass.
A visitor asks, "There are arrows on this H-R diagram showing the track this star follows. Where is the star going?"
The track doesn't show where the star is going in space, but how the star's luminosity and surface temperature will change as it ages.
Although centuries ago, astronomers thought that a nova was a new star, appearing for the first time in the heavens, today we know that it is:
a binary star system in which one star is a white dwarf and mass is being transferred to it
stars begin life as
a cloud of gas and dust
Elements heavier than iron can be created during:
a supernova explosion
Which of the following stages will the Sun definitely go through as it gets older?
all of these
The event in the life of a star that begins its expansion into a giant is
almost all the hydrogen in its core that was hot enough for fusion has been turned into helium
Why did it take astronomers until 1838 to measure the parallax of the stars?
annual shift is too small to see without a good telescope
Why do all stars spend most of their lives on the main sequence?
because the fuel for energy production in this stage of the star's life is hydrogen; and that is an element every star has lots and lots of
Two stars that are physically associated (move together through space) are called
binary stars
A visitor says, "Which color of main sequence star will become a giant star first?"
blue?
Today, astronomers can measure distances directly to worlds like Venus, Mars, the Moon, or the satellites of Jupiter by
bouncing radar beams off them
Objects that form like stars that do not have what it takes to succeed as a star (i.e. do not have enough mass to fuse hydrogen into helium at their centers) are called:
brown dwarfs
The most stable (tightly bound) atomic nucleus in the universe is:
hydrogen
when the sun reaches the end of its life, what happens to it
it loses its outer layers and leaves the core behind
Measurements show a certain star has a very high luminosity (100,000 x the Sun's) while its temperature is quite cool (3500K). How can this be?
it must be quite large in size
When a star settles down to a stable existence as a main-sequence star, which characteristics determine where on the main sequence in an H-R diagram the star will fall?
its mass
Which of the following characteristics of a single star (one that moves through space alone) is it difficult to measure directly?
its mass
Which law do astronomers use to determine the masses of the stars in a spectroscopic binary system?
keplers third law
The most common kinds of stars in the Galaxy have
low luminosity
Which of the following statements about the main sequence stage in the life of a star is FALSE?
main sequence stars are rare in the Galaxy, so we are lucky to be living around one
which property of a star determines characteristics
mass
As astronomers use the term, the parallax of a star is
one half the angle that a star seems to shift when seen from opposite sides of the Earth's orbit
The original definition of a meter was
one ten-millionth of the distance from the Earth's equator to its pole
An H-R Diagram plots the luminosity of stars against their:
temp?
An astronomical unit is:
the avg distance btw earth and sun
The measurement of cosmic distances was helped tremendously by the discovery, in the early part of the 20th century, that in Cepheid variable stars, the average luminosity was related to:
the length of time they took to vary
The higher the luminosity (intrinsic brightness) a Cepheid variable is,
the longer the period of its variations
Which of the following will show the smallest parallax shift?
the star 51 Pegasi, about 50 light years away
In a Type Ia supernova, the cause of the violent outburst is:
the transfer of so much mass from a companion star that a white dwarf goes "over the limit" and collapses, causing an enormous amount of sudden fusion
A light curve for a star measures how its brightness changes with
time
