Star Mid-life: Recap

Which of the following statements about the interstellar medium is FALSE?

• The ISM is homogenous.

• Different regions in the ISM may vary greatly in temperature.

• Generally, the ISM is very diffuse.

• The ISM consists of radiation, gas and dust.

Deep sky photos of M42 (the Orion Nebula) often show it as having a reddish hue. This is due to:

• Red giants in the nebula

• Preferential reflection of red light by dust

• Rayleigh scattering of blue light by Earth’s atmosphere

• Emission by ionised hydrogen

Which of the following correctly lists the four stages of star formation in chronological order?

• Pre-MS star, MS star, protostar, interstellar cloud

• Interstellar cloud, protostar, pre-MS star, MS star

• Interstellar cloud, pre-MS star, protostar, MS star

• Pre-MS star, interstellar cloud, protostar, MS star

A new star is born when:

• Electron degeneracy pressure is reached

• Its surface temperature reaches 3000K

• Continued gravitational contraction stops due to the start of hydrogen fusion

• The core starts to fuse He nuclei

The Hertzsprung-Russell diagram is a meaningful plot of stars, showing the relationship between stars' spectral classes / effective temperature and:

• Luminosity

• Apparent magnitude

• Mass

• Colour

 If two stars have the same size but different temperatures, the cooler star has which of the following characteristics?

• Bluer, brighter

• Redder, brighter

• Bluer, fainter

• Redder, fainter

Which pair of stars are most likely to have the same radius?

• A

• B

• C

• D

Via which processes does the Sun generate energy? You may select more than one option.

• r-process

• CNO cycle

• Proton-proton chain

• Triple-α process

Which of the following statements is true?

• Hydrogen shell fusion no longer occurs in horizontal branch stars.

• Low-mass stars can fuse elements up to iron.

• Stars transition to the red giant branch upon exhausting helium in their cores.

• All main sequence stars undergo hydrogen fusion in their cores.

When a star transitions from the sub-giant to the red giant branch, its luminosity shoots up greatly. Which of the following best explains this phenomenon?

• He shell fusion commences, which increases the star's energy output.

• The star becomes fully convective, allowing more energy to escape.

• The star becomes fully opaque, trapping radiation in its core.

• The star expands greatly, thus increasing its luminosity.