# FREE Ultimate Astronomy Questions and Answers

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#### Imagine a star with the same temperature on its surface but twice the sun's surface area. What is the energy flux at that star's surface if the energy flux at the sun's surface is Fsun?

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The energy flux at the star's surface would equal Fsun, the energy flux at the sun's surface. This is because the star's surface area is twice that of the sun, and its surface temperature is equal to that of the sun. Since the energy flux is defined as the energy radiated per unit area, the larger surface area of the star compensates for its larger size, resulting in the same energy flux as the sun.

#### A filament's initial temperature is 4000K. The filament temperature is then adjusted to 5000K by turning a knob. There is more red light emanating from the filament.

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Correct Answer: Finally, when it is at 5000K
More red light emanates from the filament when the temperature is raised from 4000K to 5000K. This is because an object emits more thermal radiation as its temperature rises. The peak wavelength of the radiation released shifts toward shorter wavelengths, which includes the red light spectrum, at higher temperatures. Consequently, the filament emits more red light due to the temperature increase.

#### The surface of the sun is a good representation of a black body. Let's say the temperature of the sun doubled overnight. In that case, which of the following claims would be accurate?

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The surface of the sun gets hotter when its temperature doubles. Wien's Law states that an object's peak radiation wavelength decreases with increasing temperature. As a result, the sun would appear bluer since its radiation peak would move closer to the low end of the spectrum. Furthermore, the total power a black body radiates is proportional to the fourth power of its temperature, as stated by Stefan-Boltzmann Law. Consequently, the sun would shine more energy when its temperature doubled.

#### Imagine a star that is twice as big as the sun and has the same surface temperature. What is the total energy emitted by a star per second if the sun emits P watts of energy every second?

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The total energy emitted by a star is directly proportional to its surface area and surface temperature. The star will release twice as much energy as the sun because it has twice the surface area and the same surface temperature. As a result, that star emits 2P watts of power every second.

#### The moon's diameter (or radius) is approximately one-fourth that of the earth. What percentage of Earth's mass would the moon's mass be if its density and that of the planet were equal?

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The moon's volume would be (1/4)^3 = 1/64 of the Earth's volume if its diameter or radius is 1/4 of the Earth's. If the moon's density were the same as Earth's, its mass would be 1/64 of the Earth's mass since density is defined as mass divided by volume. Thus, 1/64 is the correct response.

#### Like our own, the hot, dense cores of stars are surrounded by low-density gaseous atmospheres. What kind of spectrum might you see if observing the light spectrum from the sun or any other star?

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The hot, dense cores of stars, such as our sun, are surrounded by low-density gaseous atmospheres. An absorption line spectrum can be seen when examining the light spectrum emitted by the sun or any other star. This is because specific light wavelengths are absorbed by the colder gases in the star's atmosphere, resulting in dark lines or gaps in the spectrum. Because each element in the star's atmosphere has a distinct set of absorption lines, scientists can identify and learn more about the elements' characteristics.

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