One of the factors that misled Herschel into concluding that we are at the Universe's center was

Transcription

1 Homework 11! This is a preview of the draft version of the quiz Started: Apr 14 at 9:17am Quiz Instruc!ons Question 1 One of the factors that misled Herschel into concluding that we are at the Universe's center was dust that obscures the more distant stars and thereby localizes observations hot hydrogen gas in our Galaxy's disk, its emission hiding the more distant stars gravitational lensing of light by dark matter, distorting the positions of the stars some star clusters are, in reality, distant galaxies that are distributed uniformly around the Sun Question 2 Galaxies are like very big, very distant star clusters. Galaxy P is composed of yellow, orange, green and dim red stars, with a few bright, red stars and some neutron stars and black holes. Galaxy Q is composed of easily visible, bright blue stars with many dimmer red stars but no bright, red stars. Galaxy R is composed of easily visible bright, red stars with many dimmer red stars and some dimmer blue/white dwarfs but no bright, blue stars. Which galaxy is the youngest (i.e. which galaxy's stars have existed for the shortest amount of time)? Galaxy P is the youngest

2 Galaxy Q is the youngest Galaxy R is the youngest All of these galaxies are about the same age (to within a million years) Question 3 What appears to happen to a clock as it approaches and reaches the event horizon around a black hole, when viewed by a remote observer? Time appears to pass at a much faster rate, becoming infinitely fast at the event horizon Time appears to slow down and completely stop at the event horizon Time speeds up because of the strong gravitational field but does not pass infinitely fast Time passes uniformly since nothing changes the progress of time Question 4 If most of the mass of a particular galaxy was located in a big ball near the very center of the galaxy, then in the outer part of this galaxy we would expect the orbital speeds of stars to decrease rapidly with increasing distance from the galaxy's center. This behavior would be described by Newton's Third Law Wien's Law Hubble's Law Kepler's Third Law

3 Question 5 From our Galaxy's rotation curve, astronomers know that there is a large amount of dark matter distributed evenly around our Galaxy's halo. The matter is "dark" because it emits no obvious, bright light. Our Galaxy formed from a collapsing ball of gas, and stars started to form first at the outskirts of our Galaxy's halo. Given the information in this question, which of these objects certainly could NOT be a good candidate for the dark matter? Black Holes White Dwarfs Red Dwarfs A-type stars Question 6 Suppose it was possible to establish a base near the surface of a neutron star. If a yellow rocket left this base and headed away from the neutron star, what would you see? The color of the rocket would change from yellow to green and then to blue The color of the rocket would remain yellow, but the rocket would appear brighter and brighter The color of the rocket would change from yellow to orange and then to red The brightness and color of the rocket would each remain unchanged Question 7

4 Where would you look for a supermassive black hole? Orbiting a normal star in our Galaxy At the center of our Universe At the center of a galaxy At the center of a planetary nebula Question 8 Orbiting GPS satellites can precisely map locations on the Earth from the time it takes a signal to travel between the satellites and the location. Depending on the position of the satellites in the Earth's gravitational field, travel times have to be corrected by about 0.01 seconds per year. If this correction was not made, GPS directions would lead to the wrong locations on the Earth. That this correction needs to be made tests which law or theory? Wien's Law Einstein's Theory of General Relativity Kepler's Third Law Newton's Theory of Gravity Question 9 Cepheid variable stars are useful to astronomers as indicators of stars with very high-speed motion sizes, particularly of white dwarfs

5 distances, particularly to galaxies the existence of black holes Question 10 Stars in star clusters are born and arrive on the Main Sequence at roughly the same time. An astronomer observes a star cluster and notices no bright blue Main Sequence stars in the cluster. In fact, the last Main Sequence star visible in the cluster is a green star of spectral type A that has a surface temperature of about 11,000K. All other stars have turned off towards the red giant area of the H-R diagram. How long has the star cluster existed? About 30 billion years About 10 billion years About 3 billion years About 500 million years Quiz saved at 9:17am Submit Quiz