ASTR Exam 3
About two thirds of the nearby spiral galaxies don't have a round central bulge, but instead show
A central bulge with a bar of stars in the middle
In supernova like SN 1987A, once the crisis of iron fusion has begun, roughly how long does it take the star's core to collapse
A few tenths of a second
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
One of the most important observations in the history of astronomy was the one by Edwin Hubble that established that there are other galaxies, quite removed from the milkyway. How did Hubble show this
By observing a cepheid variable in a nearby galaxy and using it to get the distance
Which of the following statements about the life of a star with a mass like the sun is correct
as the star is dying, a considerable part of its mass will be lost into space
Why is it so difficult for astronomers to see new stars in the process of birth?
(All of the above) Birth happens very quickly relative to the amount of time stars spend on the main sequence Most stars are born inside dusty clouds, which block any light that may be coming from the stars The size of a newly forming star is typically quite small Protostars which are not yet doing fusion do not give off a lot of visible light
When astronomers carefully examine the planets found by Kepler and draw conclusions from the Kepler sample, what do they conclude about planets the size of Earth?
Earth-sized planets are common, but so are planets somewhat bigger than Earth
The type of galaxy that consists of almost entirely of Olaf stars and is this less blue (more yellow and reddish) than the other types is
Elliptical
Edwin Hubble was able to show that the farther a galaxy is from us, the
Faster it is moving away from us
Which of the following types of stars will spend the longest time on the main sequence
K
A star whose temperature is increasing but whose luminosity is roughly constant moves in what direction on the H-R diagram
Left
To predict wether a star will ultimately become a black hole, what is the key property of the star we should look at
Mass
What technique dud astronomers use to make the first confirmed discovery of a planet around another star like the sun?
Measure the Doppler shift of the lines in the star's spectrum and look for periodic changes in this shift due to the pull of the planet as it orbits the star
Radio astronomy has played a pivotal role in showing us the detailed structure of the Milky Way galaxy. Which of the following techniques would radio astronomer use an essential part of an investigation of this structure
Measuring the Doppler shift of a line in a radio spectrum
Astronomers were surprised to find so many Jupiter-mass planets so close to their stars. According to their best theories and models, such "hot Jupiters"
Must have formed further out from the star and must have "migrated inward" early on
Astronomers have long realized that supernovae - when they explode - give off an enormous amount of light. But observations of supernova 1987A revealed that the supernova gives off even more energy in another form?
Neutrinos
Which of the following is the smallest: -white dwarf -neutron star -red giant -main sequence star -protostar
Neutron star
Biologists tell us that life on earth took billions of years to evolve into astronomy students and other examples of intelligent life. If we want to search for planets with the intelligent life-forms that evolved over the same period of time that we did, what sorts of stars should we not bother searching around?
O and B type stars
A graduate assistant in astronomy needs to measure the mass of a spiral galaxy. Which of the following observations would be important for her to make?
Obtain the speed at which stars or gas near the outer regions of the galaxy are moving around
The central region of our galaxy is not as flat as its main disk of stars. Which of the following has roughly the same shape as our central region of stars
Peanut
Far away from a black hole, which of the following is a possible way to detect it?
Search for the flickering x-rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star
Our milkyway galaxy is what type of galaxy
Spiral
Out Milkyway galaxy is what type of galaxy
Spiral
When two identical atomic clocks, one on the ground floor and one on the top floor, we compared
The clock on the ground floor ran a tiny bit slower
When a star first begins the long path toward becoming a red giant, a layer of hydrogen around the core begins and undergo fusion throughout the main sequence stage, why is it so warm enough
The core is collapsing under its own weight and heating up from the compression; this heats up the next layer up
William Herschel thought the sun and earth were roughly at the center of the great grouping of stars we call the Milky Way. What was a key reason that Herschel did not realize our true position in the Milky Way
The dust that extends through the disk of the galaxy only allowed Hershel to see the small part of the Milky Way that surrounds us
The region around a black hole where everything is trapped, and nothing can get out to interact with the rest of the universe, is called
The event horizon
Which incident in a massive stars life sets off (begins) the very quick chain of events that leads to a supernova explosion
The fusion of iron and the rebound of neutrinos
To measure how dense a planet is (to know whether it is made of rock or gas or liquid) they must be able to measure the planet's mass from the Doppler shift and
The planet's radius using the transit method
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies
Their shape
Your sweetheart gives you a piece of gold jewelry as a present to celebrate your passing your astronomy class. Where did the gold atoms in that gift originally come from
They were built up from smaller nuclei during a supernova explosion
Which type of the following objects is considered useful to astronomers as a "standard bulb" for determining distances
Type 1a supernovae
Before you can use hubble's law to get the distance to a galaxy, what observation must you make of that galaxy
You must take a spectrum of the galaxy and measure the redshift
A type of star cluster that contains mostly very old stars is
a globular star cluster
The event in 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
According to the general of relativity, the presence of mass
causes a curvature (or warping) of spacetime
If you want to find stars that are just being born, where are the best places to search?
giant molecular clouds
What method would astronomers use to find the distance to a a galaxy so far away that individual stars are impossible to make out
finding the redshift and using Hubble's Law
What is a key reason that gravitational waves are so much harder to detect than electromagnetic waves
gravitational waves are much weaker than electromagnetic waves, and therefore require very, very precise equipment to detect
In figuring out the evolutionary tracks on the H-R Diagram, astronomers
make model stars on a computer and then follow how their characteristics will change with time
Astronomers call a ball of matter that is contracting to become a star
protostar
Astronomer have concluded that pulsars are
rotating neutron stars
A white dwarf, compared to a main sequence star with the same mass, would always be:
smaller diameter
When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that?
the ISS is falling around the Earth, and in free fall, things feel no weight
What observations about disks of dusty material around young stars suggest that planets may be forming in such disks?
the disks show lanes that are empty of dust within them
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
Recently, astronomers have observed stars and other objects that orbit the center of the Milky Way Galaxy farther out than our Sun, but move around faster than we do. How do astronomers think such an observation can be explained?
there must be a great deal of invisible dark matter outside the orbit of the Sun whose gravitational pull explains the faster motions we see out there
From which of the following will a wave of light show the greatest gravitational redshift
white dwarf
