ASTR 123 Midterm Review
what is true about the life of a star with a mass like the sun
as the star is dying, a considerable part of its mass will be lost into space
Astronomers identify the main sequence on the H-R diagram with what activity in the course of a star's life?
fusing hydrogen into helium in their cores
The most common element in the sun is
hydrogen
the most stable (tightly bound) atomic nucleus in the universe is
iron
As astronomers have learned more about the structure of the sun, they have found that it
is made entirely of hot gas
Measurements show a certain star has a very high luminosity (100,000 x the Sun's) while its temperature is quite cool (3500°K) How can this be?
it must be quite large in size
today we realize that the source of energy for the sun is a process called
nuclear fusion
the process of fusion that keeps our sun shining begins with which building blocks
two protons
When a single star with a mass equal to the sun dies, it will become a
white dwarf
In the p-p process 4H→__+2e⁺+2y+2v the missing product is
a helium nucleus
at the end of the p-p chain of nuclear fusion in the sun, hydrogen nuclei have been converted into
a helium nucleus
according to the formula E=mc²
a little bit of mass can be converted into a substantial amount of energy
which of the following, produced at the core of the sun, will take the shortest time to emerge from the sun's photosphere (surface)?
a neutrino
when the mass of a star's core is greater than 1.4 times the mass of the sun, degenerate electrons can't keep it stable as a white dwarf instead it becomes
a neutron star
Astronomers now think that there is a black hole with more than 4 million times the mass of our sun at the center of our galaxy. Roughly how large would the event horizon of such a supermassive black hole be?
about 17 times the size of the sun
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 the fusion has been turned into helium
the nucleus of the hydrogen atom
has a positive electric charge, is an ingredient in the fusion process in the sun, and is a proton
which of the following statements about the different types (shapes) of galaxies is correct
collisions and mergers between galaxies can sometimes change a galaxies type (shape)
you are alone in a large, completely dark auditorium on Earth. What kind of telescope should I use from the other side of the auditorium to detect the electromagnetic radiation emitted by your body
infrared
what happens to the positron created during the p-p chain of nuclear reactions inside the sun
it quickly collides with an electron and turns into gamma-ray energy
How long a main sequence star remains on the main sequence in the H-R diagram depends most strongly on
its mass
when a large nucleus breaks apart (or is broken apart) into two smaller pieces, this is called
nuclear fission
Where on the H-R Diagram would we find stars that look red when seen through a telescope
only on the right side of the diagram and never on the left
the sun is composed of matter in the form of a
plasma
the antimatter version of an electron is called
positron
which of the following has the longest wavelengths
radio waves
compared at the mass of our own Milky Way galaxy, the total mass we estimate for the Andromeda galaxy is
somewhat bigger
what stages will our own sun go through in the future
spending a long time on the main sequence, expanding to become red giant, eventually fusing helium into carbon, giving off a planetary nebula
our Milky Way galaxy is what type of galaxy
spiral
the type of galaxy that sometimes has a distinct bar of stars running across the central region is
spiral
which of the following is a characteristic of degenerate matter in a white dwarf star?
the electrons get as close to each other as possible and resist further compression
ninety percent of all stars (if plotted on an H-R diagram) would fall into a region astronomers call
the main sequence
the strongest force we know is
the nuclear force which holds nuclei together
a neutron star is as dense as
the nucleus of an atom
In the formula E=mc², the letter c stands for
the speed of light
Which of the following has the shortest wavelength
x-rays
objects orbiting around the center of the Milky Way obey Kepler's 3rd law. This means that
a cloud of gas or star that is further from the center will generally take more time to orbit
which type pf galaxy os observed to contain mostly older stars?
elliptical
in the sun, when a positron and en electron collide, they will produce
energy in the form of gamma rays
after the core of a massive star becomes a neutron star, the rest of the star's material
explodes outward as a supernova
