Mindblown: a blog about philosophy.
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The “Long-Haired” Comets
Learning Objectives By the end of this section, you will be able to: Comets differ from asteroids primarily in their icy composition, a difference that causes them to brighten dramatically as they approach the Sun, forming a temporary atmosphere. In some early cultures, these so-called “hairy stars” were considered omens of disaster. Today, we no…
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Asteroids and Planetary Defense
Learning Objectives By the end of this section, you will be able to: Not all asteroids are in the main asteroid belt. In this section, we consider some special groups of asteroids with orbits that approach or cross the orbit of Earth. These pose the risk of a catastrophic collision with our planet, such as the collision…
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Asteroids
Learning Objectives By the end of this section, you will be able to: The asteroids are mostly found in the broad space between Mars and Jupiter, a region of the solar system called the asteroid belt. Asteroids are too small to be seen without a telescope; the first of them was not discovered until the beginning of the…
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Thinking Ahead
Hundreds of smaller members of the solar system—asteroids and comets—are known to have crossed Earth’s orbit in the past, and many others will do so in centuries ahead. What could we do if we knew a few years in advance that one of these bodies would hit Earth? To understand the early history of life…
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For Further Exploration
For Further Exploration Articles Moons Carroll, M. “Titan: What We’ve Learned about a Strange New World.” Astronomy (March 2010): 30. Nice review of Cassini mission results. Elliot, J. “The Warming Wisps of Triton.” Sky & Telescope (February 1999): 42. About Neptune’s intriguing moon. Hayes, A., “Secrets from Titan’s Seas.” Astronomy (October 2015): 24. Good review of what we now know and…
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Planetary Rings
Learning Objectives By the end of this section, you will be able to: In addition to their moons, all four of the giant planets have rings, with each ring system consisting of billions of small particles or “moonlets” orbiting close to their planet. Each of these rings displays a complicated structure that is related to interactions between…
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Pluto and Charon
Learning Objectives By the end of this section, you will be able to: Pluto is not a moon, but we discuss it here because its size and composition are similar to many moons in the outer solar system. Our understanding of Pluto (and its large moon Charon) have changed dramatically as a result of the New…
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Titan and Triton
Learning Objectives By the end of this section, you will be able to: We shift our attention now to small worlds in the more distant parts of the solar system. Saturn’s large moon Titan turns out to be a weird cousin of Earth, with many similarities in spite of frigid temperatures. The Cassini observations of Titan…
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The Galilean Moons of Jupiter
Learning Objectives By the end of this section, you will be able to: From 1996 to 1999, the Galileo spacecraft careered through the jovian system on a complex but carefully planned trajectory that provided repeated close encounters with the large Galilean moons. (Beginning in 2004, we received an even greater bonanza of information about Titan, obtained…
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Ring and Moon Systems Introduced
Learning Objectives By the end of this section, you will be able to: The rings and moons (see the moons in Figure 12.2) of the outer solar system are not composed of the same materials as the mostly rocky objects in the inner solar system. We should expect this, since they formed in regions of lower temperature, cool…
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