Fifteen years ago, a quasar was observed that was found to be located 12 billion light years away. If our universe is approximately 15 billionyears old, when did the quasar emit the light that we observe?O A. 3 billion years agoO B. 12 billion years agoO C. 15 billion years agoOD. 15 years ago The star Sirius is about 9 light-years distant. If the speed of light were half its present value, how far away would Sirius be?A. 9 light-yearsB. 4.5 light-yearsO C. 36 light-yearsD. 18 light-years

According to the guidelines, I can answer only the 1st question.

Answered: Fifteen years ago, a quasar was…

Astronomy

1st Edition

ISBN:9781938168284

Author:Andrew Fraknoi; David Morrison; Sidney C. Wolff

Publisher:Andrew Fraknoi; David Morrison; Sidney C. Wolff

Chapter29: The Big Bang

Section: Chapter Questions

Problem 29E: There is still some uncertainty in the Hubble constant. (a) Current estimates range from about 19.9...

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Fifteen years ago, a quasar was observed that was found to be located 12 billion light years away. If our universe is approximately 15 billion years old, when did the quasar emit the light that we observe? A. 3 billion years ago B. 12 billion years ago O C. 15 billion years ago D. 15 years ago
If a galaxy is 9.0 Mpc away from Earth and recedes at 488 km/s, what is H0 (in km/s/Mpc)? km/s/Mpc What is the Hubble time (in yr)? years How old (in yr) would the universe be, assuming space-time is flat and the expansion of the universe has not been accelerating? How would acceleration change your answer? A.If the expansion of the Universe has been accelerating, the Universe could be substantially younger than the value entered above. BIf the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.
Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In this case, A. Galaxy 1 must be twice as big as Galaxy 2. B. we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2. C. we are seeing Galaxy 1 as it looked at a later time in the history of the universe than Galaxy 2. D. Galaxy 2 must be twice as old as Galaxy 1.
If you look at quasars with redshifts of 2 or so, you would be looking back to an age of quasars when they were _______________________ they are now. a. just as common as b. twice as common as c. five times as common as d. ten times as common as e. 1,000 times as common as
The Milky Way grew through merging with many smaller galaxies. What are the observational signatures of this process? O The motion of old stars in the bulge and halo of our galaxy are randomly orientated, meaning they were formed from collisions of small, accreted, galaxies all on different paths. O The ordered motion of the bulge / halo stars means that they came from many objects. The random motions of stars in the disk means it was formed from collisions of small, accreted, galaxies. O The motion of young stars in the disk are all in the same direction, meaning they came in as seperate objects.
In the standard model, about when after the Big Bang did the universe become transparent to radiation? O a.10:35 , O b.10435 O C:3x 105 y O d.103 s
The mass density of our universe is measured to be about 10-29 kg/m3. If an arbitrary point is chosen as the center, how large is the radius of a spherical surface centered at the point so that the mass enclosed in the surface will become a blackhole observed by someone outside the surface? A. 4.2 trillion light years B. 420 billion light years C. 42 billion light years D. 4.2 billion light years Is the answer D? Thanks!
Recall that Hubbleʹs law is written v = H0d, where v is the recession velocity of a galaxy located a distance d away from us, and H0 is Hubbleʹs constant. Suppose H0 = 80 km/s/Mpc. How fast would a galaxy located 800 megaparsecs distant be receding from us? A. 64 Mpc/s B. 64,000 km/s C. 0.1 times the speed of light D. 10 km/s E. 64 km/s
Hubble's First Attempt. Edwin Hubble's first attempt to measure the universe's expansion rate was flawed because the standard candles he was using were not properly calibrated. Look at (Figure 1) a.Estimate the value of Ho corresponding to the solid line in the figure. Express your answer kilometers per second per million light-years to two significant figures. b.What is the approximate age of the universe indicated by that erroneous value of Ho? Express your answer in years to one significant figure.
There is still some uncertainty in the Hubble constant. (a) Current estimates range from about 19.9 km/s per million light-years to 23 km/s per million light-years. Assume that the Hubble constant has been constant since the Big Bang. What is the possible range in the ages of the universe? Use the equation in the text, T0=1H , and make sure you use consistent units. (b) Twenty years ago, estimates for the Hubble constant ranged from 50 to 100 km/s per Mps. What are the possible ages for the universe from those values? Can you rule out some of these possibilities on the basis of other evidence?
Thinking about the ideas of space and time in Einstein’s general theory of relativity, how do we explain the fact that all galaxies outside our Local Group show a redshift?
One of the early hypotheses to explain the high redshifts of quasars was that these objects had been ejected at very high speeds from other galaxies. This idea was rejected, because no quasars with large blueshifts have been found. Explain why we would expect to see quasars with both blueshifted and redshifted lines if they were ejected from nearby galaxies.

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Fifteen years ago, a quasar was observed that was found to be located 12 billion light years away. If our universe is approximately 15 billion years old, when did the quasar emit the light that we observe? A. 3 billion years ago B. 12 billion years ago OC. 15 billion years ago D. 15 years ago