A-Level AQA Physics Classification of Stars: Describe the links between galax

Describe the links between galaxies, black holes and quasars - AQA - A-Level Physics - Question 3 - 2018 - Paper 4

Question 3

Describe the links between galaxies, black holes and quasars. Quasars are produced by (supermassive) black holes. These black holes are at the centre of (active) ga... show full transcript

Worked Solution & Example Answer:Describe the links between galaxies, black holes and quasars - AQA - A-Level Physics - Question 3 - 2018 - Paper 4

Step 1

At a distance of 5.81 × 10^8 light year, Markarian-231 is the closest known quasar to the Earth. The red shift z of Markarian-231 is 0.0415

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Answer

To estimate the age of the Universe, we can use the formula:

v = zc

where:

$v$ is the velocity of the object,
$z$ is the redshift, and
$c$ is the speed of light ( $3 × 10^8 m/s$ ).

Substituting in the values:

v = 0.0415 \times 3 × 10^8 m/s \approx 1.245 × 10^7 m/s

Next, we convert the distance into the same units as the speed:

Distance in meters:

D = 5.81 × 10^8 light years × 9.461 × 10^{15} m/light year ≈ 5.49 × 10^{24} m

Using Hubble's Law:

H_0 = \frac{v}{D}

Solving for age:

Age \approx \frac{1}{H_0}

Inserting values into the equation will yield the age of the Universe in seconds.

Step 2

A typical quasar is believed to be approximately the size of the solar system, with a power output similar to that of a thousand galaxies.

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Answer

To estimate how much further the most distant visible quasar is likely to be compared to the most distant visible galaxy, we will use the inverse-square law. The formula states:

I \propto \frac{P}{d^2}

where:

$I$ is the intensity,
$P$ is the power output, and
$d$ is the distance.

If the power of a quasar is similar to a thousand galaxies, and if we denote the power of a galaxy as $P_g$ such that:

P_q = 1000 P_g

This implies that the distance to the quasar will be greater:

d_{quasar} \approx \sqrt{1000} d_{galaxy} \approx 31.62 d_{galaxy}

Thus, the quasar is likely to be about 31.62 times further away than the most distant visible galaxy.

Describe the links between galaxies, black holes and quasars - AQA - A-Level Physics - Question 3 - 2018 - Paper 4

Worked Solution & Example Answer:Describe the links between galaxies, black holes and quasars - AQA - A-Level Physics - Question 3 - 2018 - Paper 4

At a distance of 5.81 × 10^8 light year, Markarian-231 is the closest known quasar to the Earth. The red shift z of Markarian-231 is 0.0415

A typical quasar is believed to be approximately the size of the solar system, with a power output similar to that of a thousand galaxies.

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