Download Lesson 14

Night Sky:
Astronomy: the scientific study of what is beyond Earth
Celestial object: any object that exists in space
Universe: everything that exists, including all energy, matter, and space
Star: a massive collection of gases, held together by its own gravity and emitting huge amount of energy
Luminous: producing and giving off light; shinning
Electromagnetic radiation: energy emitted from matter, consisting of electromagnetic waves that travel at the
speed of light
Electromagnetic spectrum: the range of wavelengths of electromagnetic radiation, extending from radio waves
to gamma rays, and including visible light
Aurora borealis: a display of shifting colours in the northern sky caused by solar particles colliding with matter
in Earth’s upper atmosphere
Astronomical unit: approximately 150 million kilometres; the average distance from Earth to the Sun
Solar System: the Sun and all the objects that travel around it
Satellite: a celestial object that travels around a planet or dwarf planet
Orbit: the closed path of a celestial object or satellite as it travels around another celestial object
Galaxy: a huge, rotating collection of gas, dust, and billions of stars, planets, and other celestial objects
Sun:
Mass is almost 340 000 times that of Earth, volume that is 1 300 000 times the volume of Earth.
1.5*10^8 km away from Earth
Core is the hottest part of the Sun, reaching a temperature of 15 000 000 degree Celsius
Sunspots: dark spots appearing on the Sun’s surface that are cooler than the area surrounding them
Solar flare: gases and charged particles expelled above an active sunspot
Solar prominence: low-energy gas eruptions from the Sun’s surface that extend thousands of kilometres into
space
Planet: a large, round celestial object that travels around a star
-be in orbit around a star
-have enough mass to be pulled into a stable sphere shape by gravity
-dominate its orbit (i.e., its mass must be greater than anything else that crosses its orbit)
-The four planets closest to the Sun are the terrestrial planets. These small, rocky planets are considered part of
the inner solar system. The four planets farthest from the Sun are the gas giants. These large, gaseous planets are
part of the outer Solar System.
Dwarf planet: like Pluto, it does not dominate its orbits. There are up to 2000 dwarf planets exist.
Asteroid: asteroids are small celestial objects in the Solar System composed of rock and metal. They are too
small to be considered planets.
Asteroid Belt: located between the orbits of Mars and Jupiter.
Meteoroids: smaller than an asteroid. “shooting star”. About 100 tonnes of meteoroids as small as dust particles
fall to the surface of Earth every day.
Comets: large chunks of ice, dust, and rock that orbit the Sun. Halley’s Comet is the most famous example of a
short-period comet, taking 75 to 76 years to make one trip around the Sun. The last visit of Halley’s Comet was in
1986; it will return in 2061. Comet Hale-Bopp is one of the most recent long-period comets to be observed from
Earth. It takes about 2380 years for Hale-Bopp to make one trip around the Sun.
-most comets have two tails- a gaseous tail and a dust tail.
Motions:
Earth’s Rotation: in a west-to-east direction; 1 full rotation is 1 day
Earth’s Revolution: farthest from the Sun around July 4, and closest to the Sun around January 3.
Orbital radius: the average distance between an object in the Solar System and the Sun.
Motions of the Moon: The Moon completes one rotation on its axis in about the same time it takes to complete
one revolution around Earth. The result of this is that the same side of the Moon faces Earth at all times.
Gravitational force: the force of attraction between all masses in the Universe
Earth’s Tilt: Earth’s rotational axis is tilted 23.5 degrees from the vertical when compared to the plane of Earth’s
orbit around the Sun.
Solstice: an astronomical event that occurs two times each year, when the tilt of Earth’s axis is most inclined
toward or away from the Sun, causing the position of the Sun in the sky to appear to reach its northernmost or
southernmost extreme
Equinox: the time of year when the hours of daylight equal the hours of darkness
First day of winter: December 21st
Vernal equinox: March 21st
First day of summer: June 21st
Autumnal equinox: September 21st
Precession: the changing direction of Earth’s axis
Lunar cycle: all phases of the Moon
Eclipse: a darkening of a celestial object due to the position of another celestial object
Solar Eclipse: the Sun has a diameter 400 times greater than the Moon. It is also 400 times farther from Earth
than the Moon is. As a result, the Moon and the Sun appear approximately the same size in the sky.
Moon blocking sun
Lunar Eclipse: earth blocking moon
Tide: the alternate rising and falling of the surface of large bodies of water; caused by the interaction between
Earth, the Moon, and the Sun.