Question

h-r diagram and star life cycle regents questions
mr. stabile / earth science

1. what is the ultimate fate of a star with a mass up to 8 times that of our sun after it leaves the main sequence?

(1) it becomes a red supergiant and fuses elements all the way to iron
(2) it collapses directly into a black hole
(3) it explodes in a supernova, leaving a neutron star
(4) it sheds its outer layers to form a planetary nebula, leaving a white dwarf

1. what is the initial trigger that causes a sun-like star to begin evolving into a red giant?

(1) the exhaustion of hydrogen in its core
(2) a massive increase in the stars gravitational pull
(3) the fusion of carbon into oxygen
(4) the outer layers of the star rapidly cool down

1. a star is observed to have a luminosity of 10,000 solar units and a surface temperature of approximately 11,000 k. in which category would this star most likely be classified?

(1) giant (3) white dwarf
(2) main sequence (4) supergiant

1. which of these stars would be expected to have the longest lifespan?

(1) rigel (3) sirius
(2) spica (4) barnards star

1. where on the main sequence would you find the least massive stars?

(1) in the upper-left, where stars are hot and bright
(2) mass is distributed randomly along the main sequence
(3) in the lower-right, where stars are cool and dim
(4) in the middle, where stars like the sun are located

1. according to the h-r diagram, which property is plotted on the x-axis, with its value decreasing from left to right?

(1) luminosity
(2) mass
(3) solar radii
(4) surface temperature

1. for most of its life, a very massive star is in equilibrium. what two opposing forces create this balance?

(1) magnetic fields pulling inwards and centrifugal force pushing outwards
(2) gravity pulling inwards and the pressure from nuclear fusion pushing outwards
(3) the weight of outer layers pushing inwards and the cores density resisting compression
(4) electrons repelling each other outwards and protons attracting them inwards

Explanation:

1. For a star with mass up to 8 times the Sun, after leaving the main sequence, it sheds outer layers to form a planetary nebula and leaves a white dwarf. Red supergiants (1) are for more massive stars. Collapsing into a black hole (2) or leaving a neutron star (3) require higher masses.
2. A Sun - like star starts evolving into a red giant when hydrogen in its core is exhausted. A massive increase in gravitational pull (2) is not the initial trigger. Carbon - oxygen fusion (3) happens later. Outer layer cooling (4) is not the trigger.
3. Using the H - R diagram, a star with luminosity 10,000 solar units and temperature 11,000 K is on the main sequence. Giants (1) are larger and cooler. White dwarfs (3) are dimmer. Supergiants (4) are more luminous.
4. Lower - mass stars have longer lifespans. Barnard's Star is a low - mass star. Rigel (1) and Spica (2) are massive, hot stars. Sirius (3) is more massive than Barnard's Star.
5. On the Main Sequence, the least massive stars are in the lower - right (cool and dim). Upper - left (1) has massive stars. Mass is not random (2). Middle (4) has Sun - like (medium - mass) stars.
6. On the H - R diagram, surface temperature is on the x - axis (decreasing left to right). Luminosity (1) is on the y - axis. Mass (2) and solar radii (3) are not the x - axis property.
7. For a massive star in equilibrium, gravity (inward) and pressure from nuclear fusion (outward) balance. Magnetic and centrifugal (1), outer layer weight and core density (3), electron - proton forces (4) are not the main balancing forces.

Answer:

1. (4) it sheds its outer layers to form a planetary nebula, leaving a white dwarf
2. (1) the exhaustion of hydrogen in its core
3. (2) main sequence
4. (4) Barnard's Star
5. (3) in the lower - right, where stars are cool and dim
6. (4) Surface Temperature
7. (2) gravity pulling inwards and the pressure from nuclear fusion pushing outwards