Outer Space
Space beyond Earth’s atmosphere. More broadly, the Space filling the Universe.
Universe
All of time and space.
Big Bang Theory
This theory hypothesizes that what was once a very dense mass began to expand like a balloon, with or without exploding, forming the Universe. The Universe is still expanding.
Black Hole
A dense mass, often associated with a dying star. There has been debate as to whether the Big Bang began from a Black Hole.
Galaxy
There are billions of galaxies consisting of billions of related stars in the Universe. The Sun is one of billions of related stars in a white spiral galaxy known as the Milky Way.
Star
A hot ball of glowing gases held together by its own gravity.
Solar System
A star and all the objects that travel in orbit around it. Our solar system consists of the Sun—our star—eight planets and their natural satellites (such as our moon); dwarf planets; asteroids; and comets.
Sun
The Sun’s intense energy and heat at the heart of our solar system allows for life on Earth.
Planet
A natural object in space that is massive enough for gravity to make it approximately spherical. The eight planets in our solar system include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Mercury is the smallest planet and closest to the Sun. Mars is a desert known as the Red Planet (due to iron deposits), which might have once been flooded with water. Jupiter is the largest planet. Saturn is known for its rings (of ice and rocks). Neptune is the farthest planet from the Sun.
Dwarf Planet
A dwarf planet orbits the sun but has not “cleared the neighborhood” around its orbit, because there are similar objects at approximately the same distance from the Sun. Pluto was downgraded from a planet to a dwarf planet in 2006.
Earth
Earth is the only planet in our solar system known to harbor life.
Moon
A moon is a natural satellite that orbits a planet. Earth has only one such moon. Many planets have more than one moon.
Comet
A cosmic snowball of frozen gases, rock, and dust roughly the size of a small town. When its orbit brings it close to the sun, a comet heats up and spews dust and gases into a giant glowing head larger than most planets. The dust and gases form a tail that stretches away from the sun for millions of kilometers. Halley’s Comet is visible from Earth approximately every 75 years.
Asteroids
Rocky, airless worlds that orbit the Sun, but are too small to be called planets. Tens of thousands of these minor planets are gathered in the main asteroid belt, a vast doughnut-shaped ring between the orbits of Mars and Jupiter. Asteroids that pass close to Earth are called near-earth objects.
(Much of the above is sourced from solarsystem.nasa.gov.)
Practice – Questions
1. The Big Bang Theory hypothesizes that the universe was once a very dense mass that began to:
A. die
B. go on sale
C. expand
D. contract
2. What does the above image, often associated with a dying star, represent?
A. moon
B. Earth
C. sun
D. black hole
3. What does the above image of the Milky Way represent?
A. solar system
B. galaxy
C. planet
D. dwarf planet
4. What does the above image of glowing gas, rock, and dust represent?
A. comet
B. galaxy
C. planet
D. dwarf planet
5. What does the above image of Pluto represent?
A. comet
B. galaxy
C. planet
D. dwarf planet
Practice – Answers
1. C. expand
2. D. black hole
3. B. galaxy
4. A. comet
5. D. dwarf planet