7.4 Origin of the solar system  (Page 3/27)

Today, some 4.5 billion years after its origin, the solar system is—thank goodness—a much less violent place. As we will see, however, some planetesimals have continued to interact and collide, and their fragments move about the solar system as roving “transients” that can make trouble for the established members of the Sun’s family, such as our own Earth. (We discuss this “troublemaking” in Comets and Asteroids: Debris of the Solar System .)

Key concepts and summary

Regularities among the planets have led astronomers to hypothesize that the Sun and the planets formed together in a giant, spinning cloud of gas and dust called the solar nebula. Astronomical observations show tantalizingly similar circumstellar disks around other stars. Within the solar nebula, material first coalesced into planetesimals; many of these gathered together to make the planets and moons. The remainder can still be seen as comets and asteroids. Probably all planetary systems have formed in similar ways, but many exoplanet systems have evolved along quite different paths, as we will see in Cosmic Samples and the Origin of the Solar System .

For further exploration

Articles

Davidson, K. “Carl Sagan’s Coming of Age.” Astronomy. (November 1999): 40. About the noted popularizer of science and how he developed his interest in astronomy.

Garget, J. “Mysterious Microworlds.” Astronomy. (July 2005): 32. A quick tour of a number of the moons in the solar system.

Hartmann, W. “The Great Solar System Revision.” Astronomy . (August 1998): 40. How our views have changed over the past 25 years.

Kross, J. “What’s in a Name?” Sky&Telescope . (May 1995): 28. How worlds are named.

Rubin, A. “Secrets of Primitive Meteorites.” Scientific American . (February 2013): 36. What meteorites can teach us about the environment in which the solar system formed.

Soter, S. “What Is a Planet?” Scientific American . (January 2007): 34. The IAU’s new definition of a planet in our solar system, and what happened to Pluto as a result.

Talcott, R. “How the Solar System Came to Be.” Astronomy . (November 2012): 24. On the formation period of the Sun and the planets.

Wood, J. “Forging the Planets: The Origin of our Solar System.” Sky&Telescope . (January 1999): 36. Good overview.

Websites

Gazetteer of Planetary Nomenclature: http://planetarynames.wr.usgs.gov/. Outlines the rules for naming bodies and features in the solar system.

Planetary Photojournal: http://photojournal.jpl.nasa.gov/index.html. This NASA site features thousands of the best images from planetary exploration, with detailed captions and excellent indexing. You can find images by world, feature name, or mission, and download them in a number of formats. And the images are copyright-free because your tax dollars paid for them.

The following sites present introductory information and pictures about each of the worlds of our solar system:

• NASA/JPL Solar System Exploration pages: http://solarsystem.nasa.gov/index.cfm.
• National Space Science Data Center Lunar and Planetary Science pages: http://nssdc.gsfc.nasa.gov/planetary/.
• Nine [now 8] Planets Solar System Tour: http://www.nineplanets.org/.
• Planetary Society solar system pages: http://www.planetary.org/explore/space-topics/compare/.
• Views of the Solar System by Calvin J. Hamilton: http://www.solarviews.com/eng/homepage.htm.