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Chapter 8: Problem 14

(a) What is meant by accretion? (b) Why are the terrestrial planets denser at their centers than at their surfaces?

Short Answer

Expert verified
Accretion is the process of growth or increase by gradual accumulation. It's a key mechanism through which celestial bodies form. Terrestrial planets are denser at their centers than at the surfaces because they separated into layers by density when they were forming and in a molten state. The denser materials sank to the center with the less dense materials rising to the surface.

Step by step solution

01

Understanding Accretion

Accretion refers to the process in which material, pulled in by gravitational forces, aggregates or grows. It's a key mechanism through which celestial bodies like stars, planets, and galaxies form.
02

Understanding Planetary Structure

Terrestrial planets are denser at their centers than at their surfaces because these planets are differentiated, meaning they are separated into layers by density. When they were in a molten state, the heavy materials sank to the center and the lighter ones rose to the surface.

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Most popular questions from this chapter

Because of the presence of Jupiter, the Sun moves in a small orbit of radius \(742,000 \mathrm{~km}\) with a period of \(11.86\) years. (a) Calculate the Sun's orbital speed in meters per second. (b) An astronomer on a hypothetical planet orbiting the star Vega, 25 light- years from the Sun, wants to use the astrometric method to search for planets orbiting the Sun. What would be the angular diameter of the Sun's orbit as seen by this alien astronomer? Would the Sun's motion be discernible if the alien astronomer could measure positions to an accuracy of \(0.001\) arcsec? (c) Repeat part (b), but now let the astronomer be located on a hypothetical planet in the Pleiades star cluster, 360 light-years from the Sun. Would the Sun's motion be discernible to this astronomer?

(a) Figure 8-18c shows how astronomers determine that the planet of HD 209458 has a surface temperature of \(1130 \mathrm{~K}\). Treating the planet as a blackbody, calculate the wavelength at which it emits most strongly. (b) The star HD 209458 itself has a surface temperature of \(6030 \mathrm{~K}\). Calculate its wavelength of maximum emission, assuming it to be a blackbody. (c) If a high-resolution telescope were to be used in an attempt to record an image of the planet orbiting HD 209458, would it be better for the telescope to use visible or infrared light? Explain your reasoning.

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