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# Galaxy redshifts and distances away

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Q1a)
An astronomer observes two galaxies A and B which have redshifts of:
Galaxy A = 0.08 and Galaxy B = 0.01

Which galaxy is closest to us and what is its distance away from us? You may assume that the hubble constant is H_0 = 75 km S^(-1) Mpc^(-1) and the speed of light is c= 3.0 x 10^5 km S^(-1).

Choose correct option from the italics or fill in the blanks:
The closest galaxy is Galaxy A / Galaxy B it is at a distance of ____________ Mpc.

Q1b)
Assuming that Galaxy is intrinsically of identical luminosity to Galaxy B. How does its apparent brightness on the night sky compare to that Galaxy B?

Choose correct option from the italics or fill in the blanks:
Galaxy A is ___________ times fainter / brighter than Galaxy B.
Note: please enter numbers in numerals.

https://brainmass.com/physics/galaxies/galaxy-redshifts-distances-away-345094

#### Solution Preview

Solution is attached.

Q1a)
An astronomer observes two galaxies A and B which have redshifts of:
Galaxy A = 0.08 and Galaxy B = 0.01

Which galaxy is closest to us and what is its distance waay from us? You may assume that the hubble constant is H_0 = 75 km S^(-1) 〖Mpc〗^(-1) and the speed of light is c= 3.0 x 〖10〗^5 km S^(-1).

Choose corrct option from the italics or fill in the blanks:
The closest galaxy is Galaxy A / Galaxy B it is at a distance of ____________ Mpc.

Qb)
Assuming that Galaxy A is intrinsically of identical luminosity to Galaxy B. How does its apparent brightness on the night sky compare to that Galaxy B?
Choose correct option from the italics or fill in the blanks:
Galaxy A is ___________ times fainter / ...

#### Solution Summary

This solution uses a numerical problem to illustrate how the redshifts of galaxies are related to their distances away, and subsequently their apparent brightnesses on the night sky.

\$2.19

## Collisions of planets and comets, redshift of galaxies

1. A planet orbiting a star is occasionally hit by comets. Each comet has a mass of 4.8 * 10^6 kg of which 30% is rock and 70% is water ice. Each time a comet hits the planet 40% of the mass of the comet is vaporized and the rest is added to the planet, increasing the mass of the planet. If 6 comets hit the planet every 10 years, by how much will the mass of the planet have increased in 1 million years? How much of the additional mass will be in the form of rock, assuming that the rock and ice evaporate in the same proportions as exist in the original comet? You should give both answers to one significant figure and in scientific notation.

Increase in mass of planet after 1 Million Yrs = ? kg

Additional mass of rock after 1 Million Yrs = ? kg

2. Galaxies, A and B, which have red shifts of:
Galaxy A = 0.01 and Galaxy B = 0.04. (a) Which galaxy is closest to us and what is its distance away from us?
You may assume that the Hubble constant is H0 = 75 km.s-1/Mpc and that the speed of light is c = 3.0 - 10E5 km.s-1.

a. The closest galaxy is A or B?

b. What is its distance in Mpc?

Assuming that Galaxy A is intrinsically of identical luminosity to Galaxy B, how does its apparent brightness on the night sky compare to that of Galaxy B?

c. How many times brighter or fainter is it?

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