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The smaller we feel, the more awe we experience. And who doesn’t love the feeling of awe? The following astronomical terms and ideas will help you converse fluently on the topic of the universe, but do also read The Fabric of the Cosmos by Brian Greene and Steven Hawking’s A Brief History of Time. There’s also a great memoir by Scott Kelly of living on the ISS for a year called Endurance, as well as many excellent space documentaries.
ESSENTIAL KNOWLEDGE: ASTRONOMY
Space: All of the area outside the earth’s atmosphere, whose temperatures vary from far below freezing (such as areas blocked by planets to the rays of stars) to far above boiling water (such as areas not blocked from the rays of stars)
Universe: All of the billions of galaxies in existence, which are held together by gravity. It is mostly empty space, which is why collisions are infrequent, and is constantly slowly expanding.
Star: A ball of very hot gas in space, which can be white, red, yellow or blue, depending on its surface temperature
Sun: The only star in Earth’s solar system. It is medium-sized: about 100 times the size of Earth and ten times the size of Jupiter. On its surface, it is about 5,500 degrees Celsius.
Planet: A spinning ball of rock and/or gas that travels around a star (or a black hole) in an orbit. Since they are so far away, we can only see a few outside our solar system directly.
Moon: A mini planet that revolves around a planet instead of revolving around a star. The earth’s is dry and dusty with many craters. It takes about 27 days for ours to spin once, and about 27 days for it to orbit once around the earth, which is why it doesn’t seem to be spinning. It is always facing away from us, so we’ve never seen the other side directly (though we have taken photographs). It takes about three days to reach it, depending on its placement relative to the earth in its elliptical orbit.
Solar system: A group of planets revolving around a single star or a group of stars, or a small group of stars revolving around each other. Ours contains one star, eight planets and many asteroids and comets.
Galaxy: A group of solar systems which orbit around each other. Sometimes they cross paths with each other and collide. Many contain millions of stars, and many have a black hole at their center.
Star cluster: A group of stars that forms together
Galaxy cluster: A group of galaxies held together by gravity
Supercluster: A group of galaxy clusters
The eight planets of our solar system, in order from the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. The closest four are terrestial planets, made of rock, while the further four are gas giants, made primarily of gas. Jupiter is our largest planet while Mercury is our smallest.
The eight phases of Earth’s moon: The views of the earth’s moon from the earth, which change in a 29.5-day cycle. The eight phases are: new (no visible light); waxing crescent (small sliver visible); first quarter (half moon visible); waxing gibbous (mostly visible); full (full moon visible); waning gibbous (mostly visible); third quarter (half moon visible); and waning crescent (small sliver visible).
Orbit: The circular path taken by a planet, moon, star or other celestial body. These can be maintained indefinitely because the gravity that pulls the orbiting object toward another object is balanced by the orbiting object’s momentum, which seeks to keep the orbiting object moving in a straight line. In empty space, friction, drag and other forces do not exist, so the object’s momentum is never lost.
Solar mass: The mass of the sun, which is used as a standard unit of measurement of space bodies
The Milky Way: The name of the galaxy our solar system is in. It is about 100,000 light years across and contains hundreds of billions of stars.
Andromeda: The nearest large galaxy to the Milky Way
The Local Cluster: The galaxy cluster that includes the Milky Way, Andromeda and dozens of other galaxies
One day: The unit of time marking one spin of the earth on its axis, which takes approximately 24 Earth hours. The part of the earth facing the sun has light, and the other doesn’t. It takes 365 days for the earth to orbit around the sun one time.
Light year: The distance light travels in one year (approximately 9.5 trillion kilometers, which is about 300,000,000 meters per second), which is used as a measurement of large distances in space
Solar eclipse: A celestial event during which the sun is entirely obscured from view for a short time due to the path of the moon, which brings it between the earth and the sun
Lunar eclipse: A celestial event during which the moon is mostly obscured from view for a short time due to the path of the Earth, which brings it between the moon and the sun
Asteroid: A piece of rock or metal in space that is larger than a meteoroid and smaller than a moon and revolves around the sun
Meteoroid: A piece of rock or metal in space that is the size of dust, the size of a house or anywhere in-between and revolves around the sun
Meteor: A meteoroid that burns up in a planet’s atmosphere. It is also known as a shooting star.
Meteorite: A meteoroid that hits the surface of a planet
Comet: A ball of dirty ice floating around space. When close enough to the sun, the ice melts partway and the solar wind blows a trail of gas and dust behind it, making a tail.
Nebula: A big cloud of gas and dust that stars are formed in or that formed from an exploded star
Supernova: A very large star that has reached the end of its life (and its supply of gas) and is exploding
Neutron star: The core of a supernova, which is a highly dense, rapidly rotating ball of neutrons
Pulsar: A highly magnetized neutron star that gives off waves (pulses) of radiation
Red Giant: A star that is nearing the end of its life and has swelled up and turned red
White dwarf: A hot, small star whose exterior layers have burned off during its Red Giant stage. After a time, it cools and fades away.
Binary star system: Two stars orbiting around their common center of gravity. About half of stars are part of a binary or multiple star system.
Solar wind: The stream of charged particles in the form of plasma that are continually being released from the Sun
Aurora borealis/the Northern Lights: The celestial event during which the solar wind interacts with the earth’s magnetic field and create colorful lights at the earth’s magnetic poles
The Great Red Spot: The permanent gas storm visible on Jupiter’s surface
Black hole: A supercondensed, superheavy ball of matter whose gravity pulls in nearby matter and from which nothing, not even light, can escape. Some are the remains of very large stars that, instead of dying, collapsed. Some black holes are very small, while others are several million miles across.
Singularity: A point of infinite density that exists at the center of a black hole
Event horizon: The boundary surrounding a black hole beyond which the gravitational pull is so strong that nothing, not even light, can escape. Its size is determined by the mass of the black hole.
The Big Bang theory: The most widely accepted theory regarding the creation and evolution of the universe, which states that approximately 14 billion years ago, all energy and all matter in existence were contained in a singularity, which then suddenly exploded and began to cool. As it did so, subatomic particles formed, which over time formed atoms and molecules. Eventually, gravity caused larger bits to attract smaller bits and form large stars and planets.
Dark matter: A theoretical type of matter that creates gravitational effects, but that has not yet been directly observed since it does not interact with light or any other form of electromagnetic radiation. Scientists believe that it exists partly because galaxies rotate faster than they should if visible matter is the only matter in the universe.
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