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SGBH Test 3
| Question | Answer |
|---|---|
| Which of the following statements describes Newton's First Law of Motion? | Every body continues in a state of rest or in a state of uniform motion in a straight line, unless it is compelled to change that state by a force acting on it. |
| Which of the following statements describes Newton's Second Law of Motion? | When a force F acts on a body of mass m, it produces an acceleration a equal to the force divided by the mass. Thus, a=F/m, or F=ma. |
| Which of the following statements describes Newton's Third Law of Motion? | To every action, there is an equal and opposite reaction. |
| Your weight, while standing on Earth, is the force with which_______ pulls you toward Earth's center. | gravity |
| The rate of change of the velocity of an object - speeding up, slowing down, or simply changing direction - is called the object's _________ | acceleration |
| Gravitational force can be calculated by the following formula: F = Gm^1m^2/r^2. Tripling the distance (r) between two objects will cause the gravitational force between them to ________________ | become 9 times weaker |
| What was Newton's modification to Kepler's third law? | P^2 = a^3/M, where M is the mass (of the Sun + planet), measured in Solar Masses. |
| Some space vehicles, such as the robot probes that visit other planets, attain enough speed to escape our planet's gravity and move away from Earth forever. This speed is known as the | escape speed |
| What type of star is a pulsar? | a neutron star |
| An X-ray burster intermittently produces intense bursts of X-rays. X-ray bursters are similar to recurrent novae (outburst events involving white dwarfs), in that they require that a neutron star be a member of a _______________ | binary star system |
| Gamma-ray bursts are extremely highly energetic explosions in our galaxy and other galaxies. One leading theory explains gamma-ray bursts as _____________ | The merger/collision of two neutron stars. |
| What is the typical value of the density at the center of a neutron star? | about 10^18 kg/m^3 |
| What is the value of the density at the center of a black hole? | infinity |
| Why are black holes called black holes? | their gravity prevents any form of radiation or light from escaping them |
| The equivalence principle is a major part of Albert Einstein's general theory of relativity. It states that the effects of a gravitational field are equivalent to _______________ | acceleration |
| The surface of an imaginary sphere with a radius equal to the Schwartzschild radius and centered on a collapsing star is called the __________________. It defines a region within in no event can ever be seen, heard, or known by anyone outside. | event horizon |
| Who discovered the period-luminosity relationship in Cepheid variable stars? | Henrietta Leavitt |
| How far from the center of our Galaxy does the Sun reside? | 8,000 parsecs (8 kpc) |
| Where in our Galaxy do the oldest stars reside? | in globular clusters in the Galaxy's halo |
| The observed ________________ of our galaxy provides evidence for the existence of "dark matter". | rotation curve |
| We know that a supermassive black hole must reside at the center of our Galaxy because ... | stars near the center of the Milky Way are orbiting some unseen object |
| Which type of galaxies generally do not contain flat disks of any shape? | elliptical |
| __________________ states that the farther away a galaxy is from us, the faster it appears to be moving away from us. | Hubble's law |
| Astronomers refer to this redshift (apparent change in the wavelengths of light from distant galaxies) resulting from the Hubble flow as the ______________ | cosmological redshift |
| Is the following statement true or false? "It is possible to measure the rate at which a distant galaxy is rotating." | true |
| An active galaxy refers to a galaxy that ____________________ | is undergoing extremely violent events near the galactic center, probably associated with activity of the supermassive black hole. |
| Astronomers can calculate the masses of some spiral galaxies by determining their _____________________, which plot a graph of rotation speed versus distance from the galaxy's center. | rotation curves |
| When galaxies collide, their interactions often result in galaxy-wide episodes of rapid star formation. Such a galaxy is called a __________ galaxy. | starburst |
| True or false: "Careful observations of nearby galaxies reveal that the mass of the central black hole is well correlated with the mass of the galactic bulge: higher mass central black holes are surrounded by higher mass galactic bulges." | true |
| The Local Group is part of a much larger structure (a supercluster of galaxies), which we call the _________ Supercluster. | Virgo |
| It is thought that galaxies contain visible matter (stars, nebulae, etc.), and mysterious dark matter in "halos" surrounding the visible matter. Measurements of galaxy masses and galaxy cluster masses reveal that a little more than __% of matter is dark. | 90 |
| The cosmological principle states that on very large scales, the universe is both _____________ and isotropic. | homogenous |
| The average ratio between the two values for each galaxy is called the Hubble Constant and has the currently accepted value of about ________________ | 70 km/s/Mpc, or (70 kilometers per second per million parsecs) |
| The age of the universe is approximately _______________ years. | 14,000,000,000 (14 billion) |
| Observations of distant supernovae indicate that the expansion of the universe is ___________, apparently driven by the effects of dark energy, a mysterious repulsive force that exists throughout all space. | accelerating |
| Just after the Big Bang, the universe was a hot, dense primeval fireball that emitted gamma-rays. Since then, it has cooled to the point that it primarily emits radio waves corresponding to a temperature of about ________ | 3 Kelvin |
| Globular clusters are found mainly __________________ | in the galactic halo |
| In the Milky Way Galaxy, our Sun is located _________________ | about halfway out from the center |
| A black hole with a mass of 4 Solar masses would have a Schwarzschild radius of ___________ | about 12 km |
| Consider a star in a circular orbit around a supermassive black hole at the center of a distant galaxy. If the distance from the central black hole to the star is 1,000 AU and the star orbits once every 10 years, what is the mass of the black hole? | 10 million solar masses |
| How does a galaxy with an upside-down heart shape (from a photograph that doesn't translate here) get its shape? | This is the product of the dynamic merger of two spiral galaxies. |
| A very large, perfectly spherical collection of stars would be classified as a __ galaxy. | E0 |
| What was Newton's modification to Kepler's third law? | P^2 = a^3/M, where M is the mass (of the Sun + planet), measured in Solar Masses. |
| By knowing the strength of an object's surface gravity, you can determine... (3 things) | 1. how much you would weigh if you could stand on the object, 2. how fast the object can spin before breaking apart, 3. the speed required to escape the object's gravity |
| We know that a supermassive black hole must reside at the center of our Galaxy because... | stars near the center of the Milky Way are orbiting some unseen object. |
| Why are black holes called black holes? | their gravity prevents any form of radiation or light from escaping them. |
| Which statement best describes a pulsar? | A pulsar is a neutron star, with an intense beam of radiation that flashes toward Earth each time the neutron star spins around. |
| Gravitational force can be calculated by the following formula: F = Gm^1m^2/r^2. Tripling the distance (r) between two objects will cause the gravitational force between them to ________________ | become 9 times weaker |
| A high-mass star explodes as a supernova. The star's mass, before exploding, was 20 times the mass of the Sun, but 2 Solar masses of the star's core remains after the supernova and becomes a(n) ____________ | neutron star |
| Astronomers classify different types of elliptical galaxies by _____________ | how flattened they are |
| Where in a galaxy would you find newly formed stars? | in the disk of a spiral galaxy |
| Henrietta Leavitt's work on _____________ gave astronomers like Edwin Hubble a vital tool for measuring the distances to other galaxies. | Cepheid variable stars |
| How can you measure the mass of a planet like Jupiter? | By studying the orbits of Jupiter's moons. |
| A neutron star's strong gravity is caused mostly by its small size and ______________ | large mass |
| We calculated in class that the escape speed from Earth is 11 km/s. What would be the escape speed from a planet the same size as Earth, but 4 times as massive as Earth? | 22 km/s |
| The Andromeda Galaxy is a nearby, large, spiral galaxy. The Andromeda galaxy was originally thought to be ______________ | much closer and smaller - a nebula in our own Galaxy. |
| What do Cepheid variables do? | they help measure the distance between stars |
Created by:
trinmal