Question 1

Stars with a core temperature in excess of 20 million K probably have this hydrogen fusion type:&#10;A) proton-proton&#10;B) helium&#10;C) iron&#10;D) CNO

Accepted Answer

Stars with core temperatures exceeding 20 million Kelvin primarily undergo hydrogen fusion through the CNO (carbon-nitrogen-oxygen) cycle rather than the proton-proton chain. This cycle is more temperature-sensitive and dominates in more massive stars.

Question 2

The sun is expected to live about ____ years.&#10;A) 10 million&#10;B) 10 trillion&#10;C) 10 billion&#10;D) 10 thousand

Accepted Answer

The sun, a G-type main-sequence star, has an expected lifespan of about 10 billion years, with approximately 5 billion years already passed since its formation.

Question 3

Stars with less than about 0.4 times the mass of the Sun are probably&#10;A) fully functional.&#10;B) fully convective.&#10;C) fully radiative.&#10;D) convective only in the core.

Accepted Answer

Stars with less than about 0.4 times the mass of the Sun do not have a radiative zone and are fully convective, meaning that energy is transported outward by the movement of the star's plasma rather than by radiative processes.

Question 4

The stars with the shortest main sequence lifetimes will be&#10;A) stars like the Sun.&#10;B) the lowest mass stars.&#10;C) the highest mass stars.&#10;D) the coolest stars.

Accepted Answer

The highest mass stars have the shortest main sequence lifetimes because they burn through their nuclear fuel much more rapidly than lower mass stars.

Question 5

The sun uses the _______ cycle to create most of its energy.

Accepted Answer

The answer of The sun uses the _______ cycle to...

Question 6

The balance between gravity and outward radiation pressure is called ______.

Accepted Answer

The answer of The balance between gravity and outward radiation...

Question 7

Very massive stars live relatively short lives.

Accepted Answer

Very massive stars consume their nuclear fuel much faster than smaller stars, leading to relatively short lifespans.

Question 8

The Earth's history shows temperature has remained stable due to constant increases in greenhouses gases.

Accepted Answer

Earth's temperature has fluctuated over its history due to various factors, including changes in greenhouse gas levels, solar radiation, volcanic activity, and Earth's orbit, not due to constant increases in greenhouse gases.

Deck 62: Main-Sequence Stars