Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Sample-return mission wikipedia , lookup
Scattered disc wikipedia , lookup
Planet Nine wikipedia , lookup
Heliosphere wikipedia , lookup
Kuiper belt wikipedia , lookup
Space: 1889 wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Planets beyond Neptune wikipedia , lookup
Dwarf planet wikipedia , lookup
The Solar System 09.19.07 / 09.20.07 Essential Questions What are distinguishing features of solar system bodies? What are Kepler’s laws and how do they apply to planetary motion? What is the nebular hypothesis? Overview of the solar system Solar • • • • • system includes Sun Eight planets and their satellites Asteroids Comets Meteoroids Kuiper Belt 2.8 - 4.6 billion miles away Probably tens-of-thousands of rocky, icy objects Includes Pluto Discovered circa 1992 Predicted in 1951 by Gerald Kuiper The solar system The orbits of most asteroids lie between Mars and Jupiter Minor members of the solar system Asteroids • • • • • Most lie between Mars and Jupiter Small bodies – largest (Ceres) is about 620 miles in diameter Some have very eccentric orbits Irregular shapes Origin is uncertain Image of asteroid 951 (Gaspra) Minor members of the solar system Comets • • Often compared to large, "dirty snowballs" Composition • • Frozen gases Rocky and metallic materials Minor members of the solar system Comets • Origin • • Not well known Form at great distance from the Sun Comet Hale-Bopp Minor members of the solar system Meteoroids • • • Called meteors when they enter Earth's atmosphere A meteor shower occurs when Earth encounters a swarm of meteoroids associated with a comet's path Meteoroids are referred to as meteorites when they are found on Earth Overview of the solar system A planet's • • orbit lies in an orbital plane Similar to a flat sheet of paper The orbital planes of the planets are inclined • • • Planes of seven planets lie within 3 degrees of the Sun's equator Mercury's is inclined 7 degrees Pluto's is inclined 17 degrees (That crazy Pluto) Overview of the solar system Two groups of planets occur in the solar system • Terrestrial (Earth-like) planets • • • Mercury through Mars Small, dense, rocky Low escape velocities Overview of the solar system Two groups of planets occur in the solar system • Jovian (Jupiter-like) planets • • • • • • Jupiter through Neptune Large, low density, gaseous Massive Thick atmospheres composed of hydrogen, helium, methane, and ammonia High escape velocities Pluto not included in either group (oddball) The planets drawn to scale Evolution of the planets Nebular • • hypothesis Planets formed about 5 billion years ago Solar system condensed from a gaseous nebula As the planets formed, the materials that compose them separated • • Dense metallic elements (iron and nickel) sank toward their centers Lighter elements (silicate minerals, oxygen, hydrogen) migrated toward their surfaces Kepler’s Laws Law 1: The planet orbit is ellipses with the Sun at one of two foci Law 2: The line connecting the planet to the Sun sweeps equal areas in equal time Law 3: The periods of planets’ revolutions is proportional to their distances from the Sun Law 1 http://astro.isi.edu/notes/gravity.html Law 2 http://burro.astr.cwru.edu/Academics/Astr221/Gravity/kepler2.htm Law 3 http://hyperphysics.phy-astr.gsu.edu/hbase/kepler.html Eight or Nine? Pluto • • • Discovered in 1930 Highly eccentric orbit causes it to occasionally travel inside the orbit of Neptune, where it resided from 1979 through February 1999 Moon (Charon) discovered in 1978 Pluto and its moon Charon as compared to the size of Earth A decision to make With the discovery of the Kuiper Belt, astronomers need to make on of two choices: allow the possibility of many, many more planets create a more restrictive definition of planet They chose this second option They then created possible definitions Potential definition 1 A planet would need to a) revolve around a star, b) be massive enough to have formed into a round shape, c) not be a moon, and d) not be another star This option would have resulted in 12 planets, with more possible in the future Potential definition 2 The same as the first with one addition the planet must have “cleared the neighborhood around its orbit.” Because Pluto’s orbit crosses paths with Neptune, it would not qualify This definition results in 8 planets This is the one the International Astronomical Union chose to accept Pluto hasn’t changed, just our definition of planet Light pollution http://epod.usra.edu/archive/epodviewer.php3?oid=92448 Source: University of Hawaii Houses cause pollution too Better lighting Source: NASA see also p. 664 in home text Resources International Dark-Sky Society International Astronomical Union Light Pollution Abatement Program (LPAP) Canada