Download PS Astronomy Notes part 5 (1/20, 2 pages, PDF)

Notes # ____
Chapter 16 Notes, part V
Date: _______
16.3: The Solar System
Our Solar System is comprised of ____ ___________, primary bodies ________________
around the sun; the _________________ _________, a collection of small, rocky objects found
between the orbit of _______ & _________________; and a few other small orbiting objects
such as __________, ___________________ and objects located in the distant ____________
______ that includes the dwarf planet ____________.
All of the planets move in __________________ orbits around the sun, with the sun located
at one of the two “__________” of an ellipse as shown:
Sun
When a planet is at its closest approach to the sun in its orbit it is said to be at
________________ (this occurred January 5th); when a planet is furthest away from the sun
it is said to be at _________________ (this year it will be on July 6th).
Planets can only be
seen because they _______________ sunlight. Only ______________, __________, _________,
______________ & _____________ can be seen from Earth without a telescope.
The first planet discovered outside of our own solar system (in 1995) was 51 Pegasi b, also
called Bellerophon (or 51 Peg b). Astronomers have discovered 3035 planets outside of our
solar system called ___________________ (see http://planetquest.jpl.nasa.gov/ for more
info!). Most of these are very large planets, called “super-Jupiters” that orbit very close to
their star. A few of them are smaller, and just this past December two were discovered by
the Kepler Space Telescope to be as small as the Earth!
The planets in our solar system are divided into two distinct categories:
the ____________ or ____________________ planets: Mercury, Venus, Mars & Earth; and
the ____________ or ____________________ planets: Jupiter, Saturn, Neptune and Uranus.
A few years ago, after the discovery of an object outside of Pluto’s orbit, a new definition of
planets was created. Pluto was no longer a planet but it, and the largest asteroid, Ceres,
are now classified as “dwarf” planets. Other dwarf planets include Eris, Haumea,
MakeMake. (note: any dwarf planet outside of Neptune’s orbit are called _________
__________________ _______________--TNO’s--or _______________).
The inner planets are smaller and have a _________, _________ surface. They show no signs
of _________ and have few, if any, ___________ (Earth–1, Mars–2). ____________ is the
largest, heaviest and most dense. The further from the sun the longer its _______ (or time
to complete one ________). Mercury’s year is 88 Earth days long; Venus, 225; Earth, 365,
Mars, 687. Each planet also spins, or ____________, on its own axis. The amount of time
this takes is called the planet’s _______. This varies greatly and has no bearing on how far
from the sun: Earth rotates every 24 hours;; Mars’ day is 30 minutes longer than Earth;
Mercury’s day is 59 “Earth days” long whereas Venus has a most bizarre day: it is 243 days
--longer than its year!--and backwards, so the sun rises in the west and sets in the east!
Mercury has a very wide temperature range, from almost 400 °C on the “sunny” side
to as low as -170 °C on the nighttime side. This is due to its long day and no atmosphere
to trap heat at night.
Venus is the hottest planet overall due to its very long day and incredibly thick
atmosphere, nearly 100 times more dense than Earth’s. On average Venus temperatures
exceed 400 °C. Venus is very similar to Earth in size, mass, density and surface features
and is often considered as Earth’s (Evil) Twin.
Mars on the other hand is cold and lacks much of an atmosphere. There are ice caps
at the poles and maybe some ice or even liquid water under its surface. There are two
NASA spacecraft currently traversing Mars looking for signs of water and/or life. The
surface of Mars is also similar to Earth, complete with dried river beds, canyons, plains
and mountains. The largest and tallest mountain in the solar system, ______________
________ (nearly 85,000 feet tall), is found on Mars.
Separating the inner and outer planets is a region called the _______________
_______ comprised of millions of small rocky objects thought to have been the remains of a
planet that did not have a mass to sufficiently form. Most of these objects orbit the sun
between ______ and _____________ and are more correctly called the _______ ________
__________________ but others orbit nearer the Earth called _______ _________ ___________
(or NEO’s) or sometimes __________ ______________.
The Outer planets are very large (between ____ and ____ times the Earth’s diameter),
massive (between _____ and _____ the Earth’s mass) but mostly gaseous so very low in
density. In fact _____________ is less dense than water so it would float in a big enough
ocean! All of the outer planets have short days (ranging from 9.9 hours on Jupiter to 17
hours on Neptune) but long years: Jupiter, 12 years; Saturn, 29.5 years; Uranus, 84 years;
and Neptune 165 years. All of the outer planets have _______ and many ________.
Pluto is an oddball--it is probably a captured orbiting body caught in the sun’s
gravitational field. It orbits the sun every 249 years and during 20 of those years it is
actually closer to the sun than Neptune!