8 2 stellar evolution

The colour of a star tells us about its surface temperature.

False. The hottest stars are blue, whereas the coolest stars are red.

A white dwarf has a hotter surface temperature than a red giant.

True. As a star expands, its surface cools and becomes redder.

True. All stars follow the same initial stages in their life cycle: The stages that follow depend on the mass of the main sequence star that forms.

The forces acting on a star in a stable state are:

The stages, in the correct order, in the life cycle of a star similar to the Sun are:

A protostar becomes a main sequence star when nuclear fusion reactions are initiated in its core and the inward force of gravity is balanced by the outward pressure from the fusion reactions.

A main sequence star turns into a red giant when hydrogen in the star's core begins to run out and the star begins to fuse helium into heavier elements.

False. A high mass star will eventually explode as a supernova and become a neutron star or a black hole.

The stages, in the correct order, in the life cycle of a star with a mass larger than the Sun are:

A supernova is a large exploding star.

A supernova occurs when a star much more massive than the Sun reaches the end of its red supergiant stage. It collapses, becomes very unstable and explodes.

Luminosity is the total amount of light energy emitted by a star.

Apparent magnitude is the perceived brightness of a star as seen from Earth.

Absolute magnitude is a measure of how bright stars would appear if they were all placed the same distance away from the Earth.

The two factors that influence the apparent magnitude of a star are

The apparent magnitude scale shows that:

It is difficult to measure the brightness of stars directly because a distant bright star might appear to have the same brightness as a nearby dim star.

False. An object with an apparent magnitude of +10 is dimmer than an object with an apparent magnitude of -10. This is because the brighter the star, the smaller the magnitude.

The Hertzsprung-Russell (HR) diagram is a plot of a star's luminosity on the y-axis and its surface temperature on the x-axis.

The star with the highest surface temperature is star B. The hottest stars are located towards the left side of the H-R diagram.

The star with the coolest surface temperature is star D. The coolest stars are located towards the right side of the H-R diagram.

The brightest star is star A. The brightest stars are found near the top of the H-R diagram.

The most similar star to the Sun is star C. The luminosity scale is given in solar units, where the luminosity of the Sun = 1

On the H-R diagram, main sequence stars are stars found in a band from the top left to the bottom right.

On the H-R diagram, white dwarfs are located below the main sequence and slightly to the left.

On the H-R diagram, red giants are located above the main sequence and slightly to the right.

The hottest and dimmest stars on the H-R diagram are white dwarfs.

The coolest and brightest stars on the H-R diagram are red supergiants.