Hubble's law

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.

Figure 2 shows, for some galaxies, how their recession speed v varies with distance d from the Earth.

Estimate, using Figure 2, the age in seconds of the Universe.

The estimate in Question 05.1 assumes that the Universe has expanded at a constant rate. Measurements involving type 1a supernovae that are at large distances from Earth caused astronomers to make a modification to this assumption.

State:

• the modification

• the explanation that was proposed to account for this modification.

In the middle of the 20th century, there were two competing theories of the Universe. In 1964, electromagnetic radiation was observed coming from all directions in space. Figure 2 shows the distribution of this radiation as observed from Earth.

The graph provides evidence for one of these theories of the Universe.

Discuss the main features of this theory of the Universe.

In your answer, you should include:

• the main predictions and evidence for the theory, and

• a suitable calculation.

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.

Type 1 a supernovae can be used as standard candles.

State what is meant by a standard candle.

Sketch on Figure 2 the light curve for a type 1 a supernova. Annotate your graph with suitable scales and a unit for time.

Measurements of type 1 a supernovae are used to find a value for the Hubble constant.

The distance from Earth is known for many type 1 a supernovae.

Describe how these values of distance are used, with other data, to find the Hubble constant.

Your answer should include:

• the other data needed and how these data are used

• the graph plotted, including appropriate units for the axes

• how the Hubble constant is obtained and any limitations on the result.

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.

Evidence to support the Big Bang theory comes from cosmological microwave background radiation and the relative abundance of hydrogen and helium in the Universe.

Explain what is meant by cosmological microwave background radiation and how its existence supports the Big Bang theory.

Explain how the relative abundance of hydrogen and helium supports the Big Bang theory.