Question

base your answers to questions 19 through 21 on the passage below and on your knowledge of earth science. the passage describes the life - cycle of a sun - like star.
the life cycle of a sun - like star
stars like the sun begin as a nebula, which is a large cloud of gas and dust. under the right conditions, the nebula begins to shrink and due to slow - mass brightness. this protostar, or early star, may reach a surface temperature of 5600 k, and its luminosity equal to the sun. after most of the hydrogen in the core is used up, a series of changes first causes the star to collapse, then greatly expand beyond its original size as the surface temperature lowers to 3000 k and the luminosity increases to 2000 times greater than the sun. as the star reaches the end of its supply of nuclear fuel, its size changes to an equatorial diameter similar to the size of earth. the surface temperature will be approximately 13,000 k and the luminosity will decrease to 0.001 that of the sun.

1. from the information given in the passage above, complete the table by matching the stage of star development listed to its description. each stage will be used only once.

choose from the following:

• sun - like star
• nebula
• red giant star
• white dwarf
• protostar

steps in the lives of sun - like stars

step	description	stage of star development
2	surface temperature: 3000 k, luminosity: 10 x sun	protostar
3	surface temperature: 5500 k, luminosity: 1 x sun	sun - like star
4	surface temperature: 3000 k, luminosity: 2000 x sun	red giant
5	surface temperature: 13,000 k, luminosity: 0.001 x sun	white dwarf

1. state the two balancing forces of a main sequence star. 1) __________ 2) __________
2. which star is most likely to explode to a supernova? (1) sun (2) ross 128 (3) antares (4) vega
3. what occurs to the temperature and luminosity of a star as it enters its intermediate stage?

temperature __________ luminosity __________

1. in the final stage of a red supergiant, what stable element is formed in the star’s core through the process of nucleosynthesis?

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life cycles of stars model

Explanation:

Step1: Identify forces in main - sequence star

In a main - sequence star, the inward pull of gravity is balanced by the outward pressure from nuclear reactions.

Step2: Answer question 20

The two balancing forces are gravitational force and the pressure from nuclear reactions.

Step3: Analyze supernova - likely stars

Stars much more massive than the Sun are likely to explode as supernovas. Antares is a very massive star compared to the Sun, Ross 128 is a low - mass star, and Vega is not as massive as Antares in the context of supernova formation.

Step4: Answer question 21

Antares is most likely to explode as a supernova, so the answer is (3) Antares.

Step5: Consider star's intermediate stage

As a star enters its intermediate stage, it may expand and cool. The temperature decreases and the luminosity increases.

Step6: Answer question 22

Temperature: decreases; Luminosity: increases

Step7: Recall nucleosynthesis in red supergiant

In the final stage of a red supergiant, iron is the stable element formed in the star's core through nucleosynthesis.

Step8: Answer question 23

Iron

Answer:

1. 1) Gravitational force; 2) Pressure from nuclear reactions
2. (3) Antares
3. Temperature: decreases; Luminosity: increases
4. Iron