Question

use your answers to questions 19 through 23 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 in space. under the right conditions, a clump in the nebula begins to rotate, contract, and heat up, causing the gas (mainly hydrogen) and dust to glow more brightly. this protostar, or early star, may reach a surface temperature of 3000 k with a luminosity 10 times greater than the sun. as the protostar continues to collapse, heat and pressure in it ever become so great that nuclear reactions begin to use the hydrogen as fuel to produce energy, and the protostar becomes a star. the pressure created by nuclear reactions in the stars core pushes outward and exactly balances the inward pull of gravity. this balance between forces allows the star to maintain a certain size and brightness for about 80% of its life. the star may reach a surface temperature of 5500 k and a 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<br>luminosity: 10 x sun
3	surface temperature: 5500 k<br>luminosity: 1 x sun
4	surface temperature: 3000 k<br>luminosity: 2000 x sun
5	surface temperature: 13,000 k<br>luminosity: 0.001 x sun

1. state the two balancing forces of a main sequence star. 1) __________ 2) __________
2. which star is most likely to explode to a supernova?<br>(1) sun (2) ross 128 (3) antares (4) vega 21__<br>22. what occurs to the temperature and luminosity of a star as it enters its intermediate stage?<br>temperature ________________ luminosity __________________
3. in the final stage of a red supergiant, what stable element is formed in the stars core through the process of nucleosynthesis? ____________

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Explanation:

Step1: Analyze step 2 in the table

A protostar can reach a surface - temperature of 3000 K and a luminosity 10 times that of the Sun. So, the stage for step 2 is protostar.

Step2: Analyze step 3 in the table

A Sun - like star in its main - sequence phase can have a surface temperature of 5500 K and a luminosity equal to the Sun. So, the stage for step 3 is Sun - like star.

Step3: Analyze step 4 in the table

A red giant star has a lower surface temperature (around 3000 K) and a high luminosity (2000 times the Sun). So, the stage for step 4 is red giant star.

Step4: Analyze step 5 in the table

A white dwarf has a high surface temperature (about 13000 K) and a very low luminosity (0.001 times the Sun). So, the stage for step 5 is white dwarf.

Step5: Answer question 20

The two balancing forces of a main - sequence star are the pressure created by nuclear reactions in the star's core (outward force) and the inward pull of gravity.

Step6: Answer question 21

Antares is a red supergiant and is most likely to explode as a supernova. Massive stars like red supergiants have the potential to end their lives in a supernova explosion. The Sun is a smaller, less massive star and will not explode as a supernova. Ross 128 is a low - mass star and also will not go supernova. Vega is a main - sequence star but not as massive as Antares.

Step7: Answer question 22

As a star enters its intermediate stage (becoming a red giant), its temperature decreases and its luminosity increases.

Step8: Answer question 23

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

Answer:

19.

• Step 2: protostar
• Step 3: Sun - like star
• Step 4: red giant star
• Step 5: white dwarf

20.

• 1) Pressure from nuclear reactions
• 2) Inward pull of gravity

1. (3) Antares

22.

• temperature: decreases
• luminosity: increases

1. iron