Quasars

The galaxy M87 is at a distance of 5.3 × 10⁷ ly from the Earth.

Determine, in m s⁻¹, the recessional velocity of M87 relative to the Earth.

Astronomers believe that M87 has an active supermassive black hole at its centre.

Suggest one observation that leads to this conclusion.

Which provides evidence for the existence of dark energy?

Tick (✓) one box.

The Earth is in the galaxy known as the Milky Way. The Andromeda Galaxy is one of the closest galaxies to the Milky Way.

The Andromeda Galaxy approaches the Milky Way at a speed of 110 km s⁻¹. The distance between the galaxies is 770 kpc.

Discuss whether these data can be used to estimate an age for the Universe.

There is a supermassive black hole at the centre of the Andromeda Galaxy. The mass of this black hole is 1.60 × 10⁸ solar masses.

Calculate the radius of the event horizon of this black hole. State an appropriate unit for your answer.

Scientists predict that a quasar will be produced as the Milky Way and the Andromeda Galaxy merge.

Explain what is meant by a quasar. Go on to suggest why a quasar may be produced as galaxies merge.

In your answer you should:

• describe the typical properties of a quasar

• explain how observations of quasars provide evidence for these properties

• suggest the process of quasar formation that is likely when two galaxies merge.

C 273 was the first quasar to be discovered. IC 1101 is one of the largest galaxies known. Table 2 shows some information about these objects.

State the property of the quasar that led to its discovery.

Show that the absolute magnitude X of quasar 3 C 273 is about −27

Assume that the quasar and the galaxy are both viewed from the same distance.

Explain which would be the brighter object.

The black hole at the centre of IC 1101 has a mass of 7.1 × 10¹¹ M_S

Calculate the average density within the event horizon of the black hole.

IC 2497 is a galaxy that contained a quasar. It is believed that the quasar stopped emitting radiation several thousand years ago.

Suggest why the quasar stopped emitting radiation.

IC 2497 has a red shift of 0.0516

Determine the distance from the Earth to IC 2497. Give an appropriate unit for your answer.

Table 3 contains information about two galaxies.

Discuss whether these data are consistent with Hubble’s Law.

Quasars are the most distant measurable objects.

Discuss one problem associated with the determination of the distance from the Earth to a quasar.

Describe the links between galaxies, black holes and quasars.

At a distance of 5.81 × 10⁸ light year, Markarian-231 is the closest known quasar to the Earth. The red shift z of Markarian-231 is 0.0415

Use these data to estimate an age, in seconds, of the Universe.

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.

Estimate, with reference to the inverse-square law, how much further the most distant visible quasar is likely to be compared to the most distant visible galaxy.