Page 33 - Curriculum Visions Dynamic Book. To close the book, close the tab.

North Star
(See: Polaris.)
Nova
A nova is a binary star in which the stars interact to release enormous amounts of energy in an unpredictable way.
O
Omega Centauri
The brightest cluster of stars in the sky. It may contain millions of old stars.
Orbit
The path of an object that is moving around a second object or point.
Everything in the Universe contains a pull, or a force, we call gravity. The bigger the body, the bigger the force of gravity it has. The Moon is only one-eighth the mass of Earth, and so it has one- eighth the pull of Earth’s gravity. The Sun is big enough for its pull of gravity to spread out all the way to Pluto, some 6 billion km.
Gravity would pull the planets and their moons into the Sun if
they were not moving in curved— circular or elliptical (oval)—paths, or orbits. The orbits throw the planets away from the Sun and thus balance out the pull from the Sun. The orbit of the Earth around the Sun takes about 365 days to complete (actually 365.25, so that every four years there is one extra day—the leap year).
The Moon would be pulled into the Earth if it, too, were not in a curved orbit. The Moon orbits the Earth once every 28 days. This is called a lunar month. (See also: Apse; Earth orbit; Geostationary
Orbit
Pluto
Jupiter
Asteroid belt
Saturn Uranus
Neptune
orbit; Precession.)
 Orbit—The diagram shows the orbits of the planets. The orbits of the inner planets have been enlarged in the bottom part of the diagram for clarity.
The outer planets
Earth
Mercury
Sun
Venus
Mars
The inner planets
33