Astronomy 123 Midterm #1
the nucleus of an atom
A neutron star is as dense as
the Cepheid variables
A type of star that has turned out to be extremely useful for measuring distances is
a little bit of mass can be converted into a substantial amount of energy
According to the formula E=mc^2
explodes outward as a supernova
After the core of a massive star becomes a neutron star, the rest of the star's material
is made entirely of hot ionized gas
As astronomers have learned more about the structure of the sun, they have found
rotating neutron stars
Astronomers have concluded that pulsars are
fusing hydrogen into helium in their cores
Astronomers identify the main sequence on the H-R diagram with what activity in the course of a star's life?
these bursts most likely come from the merger of two neutron stars
Astronomers now have a good idea for explaining how the short-duration gamma-ray bursts might come about. Which of the following is part of their explanation?
about 17 times the size of the Sun
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?
A helium nucleus
At the end of the p-p chain of nuclear fusion in the Sun, hydrogen nuclei have been converted into:
somewhat bigger
Compared to the mass of our own Milky Way Galaxy, the total mass we estimate for the Andromeda Galaxy is
the faster it is moving away from us
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the
the gamma-rays came from all over the sky, not just the plane of the Galaxy
How did observations show that gamma-ray bursts were not coming from the Milky Way Galaxy?
at the speed of light
How fast do electromagnetic waves travel?
at the speed of light
How fast do radio waves travel?
its mass
How long a main sequence star remains on the main sequence in the H-R diagram depends most strongly on
neutrons and neutrinos
In a collapsing star of high mass, when electrons and protons are squeezed together with enormous force, they turn into:
the transfer of so much mass from a companion star that a white dwarf produces an enormous of fusion
In a type 1a supernova, the cause of the violent outburst is:
The speed of light
In the formula E=mc^2, the letter c stands for
a helium nucleus
In the p-p process, the missing product is
energy in the form of gamma rays
In the sun, when a positron and a electron collide, they will produce
It must be quite large in size
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?
the main sequence
Ninety percent of all stars (if plotted on an H-R diagram) would fall into a region astronomers call:
a cloud of gas or star is further from the center will generally take more time to orbit
Objects orbiting around the center of the Milky Way obey Kepler's 3rd Law. This means that
spiral
Our milky way galaxy is what type of galaxy?
his particular nearby galaxy is moving toward us
The Andromeda Galaxy (our nearest spiral neighbor) has spectral lines that show a blue shift. From this we may conclude that:
positron
The antimatter version of an electron is called a
the same luminosity
The apparent brightness of stars in general tells us nothing about their distances; we cannot assume that the dimmer stars are farther away. In order for the apparent brightness of a star to be a good indicator of its distance, all the stars would have to be:
Hydrogen
The most common element in the sun is
iron
The most stable (tightly bound) atomic nucleus in the universe is:
has a positive electrical charge, is an ingredient in the fusion process in the sun, a proton
The nucleus of the hydrogen atom
two protons
The process of fusion that keeps our sun shining begins with which building blocks
the nuclear force which holds nuclei together
The strongest force we know is
spiral
The type of galaxy that sometimes has a distinct bar of stars running across the central region is
it quickly collides with an electron and turns into gamma-ray energy
What happens to the positron created during the p-p chain of nuclear reactions inside the sun?
½ the diameter of the Earth's orbit around the Sun
What is the baseline that astronomers use to measure the parallax (the distance) of the nearest stars?
finding the redshift and using Hubble's Law
What method would astronomers use to find the distance to a galaxy so far away that individual stars are impossible to make out (resolve)?
nuclear fission
When a large nucleus breaks apart (or is broken apart) into smaller pieces, this is called
white dwarf
When a single star with a mass equal to the Sun dies, it will become a
a neutron star
When the mass of a star's core is greater than 1.4 times the mass of the sun, degenerate electrons cant keep it stable as a white dwarf. Instead, it becomes
radio waves
Which of the following has the longest wavelength?
the electrons get as close to each other as possible and resist further compression
Which of the following is a characteristic of degenerate matter in a white dwarf star?
type 1a supernova
Which of the following objects is considered useful to astronomers as a "standard bulb" for determining distances?
collisions and mergers between galaxies can sometimes change a galaxy's type (shape)
Which of the following statements about the different types (shapes) of galaxies is correct?
as the star is dying, a considerable part of its mass will be lost into space
Which of the following statements about the life of a star with a mass like the Sun is correct?
a neutrino
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
Which of the following, produced at the core of the Sun, will take the shortest time to emerge from the Sun?
elliptical
Which type of galaxy is observed to contain mostly older stars?
infrared
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
Positron
the antimatter version of an electron is called
the nuclear force which holds nuclei together
the strongest force we know is
plasma
the sun is composed of matter in the from of a
Nuclear fusion
today we realize that the source of energy for the Sun is a process called