Chapter 23 Quiz

Elements heavier than iron can be created during:

a supernova explosion

Astronomers have noticed that the visible filaments in the Crab Nebula are moving towards us at great speed. How can they know about motions like this?

from the Doppler shift in the line radiation from the nebula

Compared to the star it evolved from, how would you describe a white dwarf?

hotter but less luminous

A star with a mass like the Sun which will soon die is observed to be surrounded by a large amount of dust and gas -- all material it has expelled in the late stages of its life. If astronomers want to observe the radiation from such a giant star surrounded by its own debris, which of the following bands of the spectrum would be the best to use to observe it?

infrared

the most stable (tightly bound) atomic nucleus in the universe is:

iron

the age of a star cluster can be determined from:

main sequence turnoff

A white dwarf, compared to a main sequence star with the same mass, would always be:

smaller in diameter

Astronomers observe a young cluster of stars, where stars with three times the mass of the Sun are still on the main sequence of the H-R diagram. Yet the cluster contains two white dwarfs, each with a mass less than 1.4 times the mass of the Sun. If we can show that the white dwarfs are definitely part of the cluster, how can their presence so soon in the life of the cluster be explained?

stars lose a lot of mass on their way to becoming white dwarfs; and so the white dwarfs could have started out as quite massive stars

If observations of supernovae in other galaxies show that such an explosion happens in a spiral galaxy like the Milky Way on average every 25 to 100 years, why have astronomers on Earth not seen a supernova explosion in our Galaxy since 1604?

the disk of our Galaxy contains a great deal of dust, which tends to block the light of supernova explosions from more distant parts of our Galaxy

What is a planetary nebula?

the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star

a neutron star is as dense as

the nucleus of an atom

When a star undergoes a nova explosion, it may return to its "quiet state" and later become a nova again. What would allow a nova explosion to happen to a star more than once?

the star that goes nova has a companion star near it, which dumps material onto the first star and continues to do so even after the fist nova explosion

Where are red giants on the H-R diagram?

top-right

when a single star with a mass equal to the sun dies, it will become a

white dwarf