Honors Unit 1: Earth in Space and Time 23-24 Test Study Guide

Asteroid

A solid, rocklike mass that revolves around the sun. originte & typically orbit within region between Mars and Jupiter.

Astronomical Unit

The average distance between Earth and the sun, about 150 million kilometers.

Big Bang Theory

Theory of creation of Universe by expansion of an extremely small single mass of extremely high density and temperature.

Comet

A mass of rock, ice, dust, and gas traveling around the sun usually in a highly eccentric orbit most originate from region beyond neptune.

Galaxy

A group of millions, even billions, of stars, held together by gravity.

Hypothesis

A model/explanation based on oberved facts but not yet tested

Light Year

The distance that light travels in a year, about 9.5 trillion kilometers.

Local Group

Group of nearby galaxies that the milky way belongs to.

Meteor

The light a meteoroid creates as it passes through Earth’s atmosphere.

Meteorite

The part of a meteoroid that survives its trip through the atmosphere and strikes Earth’s surface.

Meteoroid

Umbrella term for all fragments that travel though space and sometimes our atmosphere.

Nebula

A large cloud of dust and gas in space.

Planet

A celestial object that revolves around the sun, is is a spheroid, and has cleared most of its orbit of large debris.

Proxima Centauri

The next closest star to Earth (other than Sun), 4.3 light years away.

Solar system

The sun and its family of orbiting planets, and other debris left over from the disk.

Super Nova

Brilliant burst of light that follows the collapse of the core and explosion of a massive star.

Tunguska

Siberian site where an asteroid struck in 1908 with power of 1000 atomic bombs.

Independent Variable

The variable in an experiment that is manipulated by the experimenter; the variable being tested to see if it causes the expected result.

Dependent Variable

The experimental factor that is being measured; the variable that may change in response to changes of the independent variable.

Virgo Supercluster

The super cluster of galaxies of which our local group is a member. Contains roughly 2000 galxies.

Universe

Everything. All existing matter, space, time, and energy.

Star

A mass of incandescent gas, where a balance exists between the nuclear reactions pushing outward from the interior and the gravitational forces pushing inward.

Milky Way Galaxy

The galaxy that contains our solar system. Spiral shaped with at least 3 arms, billions of stars in a disk 100,000 ly across and 10,000 ly thick at the galactic bulge center.

Galaxy Cluster

Groupings of galaxies that are gravitationally bound and travel through space together.

The Drake Equation

Calculates the probability used to estimate the number of extraterrestrial civilizations in the solar system.

Edwin Hubble

An astronomer who discovered in 1929 that galaxies are receding from us at a speed proportional to their distance (Hubble’s Law) which lead to the conclusion that our universe was expanding.

Cecilia Payne-Gaposchkin

Discovered the hydrogen (H) and helium (He) rich composition of matter in space which is evidence for the Big Bang Theory.

Penzias and Wilson

Scientists who discovered cosmic background radiation in 1964. One of the 3 main lines of evidence that support the Big Bang theory.

Planetary Accretion

The process by which planets grow through collisions and sticking due to gravity and chance.From planetary embryos to planetesimals to protoplanets to true planets.

Jovian Planet

Jupiter-like planets Jupiter, Saturn, Uranus and Neptune.

Terrestrial Planet

Earth-like planets: Mercury, Venus, Earth, Mars.

Cosmic Background Radiation

Discovered by Penzias & Wilson in 1964. Radiation left over from the early development of the universe, predicted by supporters of Big Bang over steady state model.

Kuiper Belt

A region outside the orbit of Neptune where most short-period comets are thought to originate.

Dwarf Planet

A spheroid celestial body revolving around the sun, similar to a planet, but not large enough to have gravitationally cleared its orbit. Category Pluto belongs in.

Doppler effect

The apparent change in wavelength of radiation caused by the relative motions of the source and the observer.

Spiral Galaxy

A galaxy with a bulge in the center and very distinctive spiral arms. Our Milky Way is a spiral galaxy.

Elliptical galaxy

A galaxy that has a round or elliptical outline. It contains little gas and dust, no disk or arms, and few hot, bright stars.

Irregular galaxy

A galaxy that has an undefined shape; irregular galaxies have large numbers of young stars and greats amounts of gas and dust are usually found near larger galaxies.

Conservation of Angular Momentum

The law of physics stating that the total amount of angular momentum in an isolated system remains constant. Cam=mass x width x velocity. This predicts the rotational velocity changes that occur as width or mass of the rotating body are changed.

Neutron Star

The very small, very dense core of a massive star, left behind after a supernova.

Singularity

An infinitely small point which contained all the of the Universe at the beginning of time. Also refers to the single point of intense gravity left behind after a very massive star dies.

Black Hole

A point in space with a gravitational field so strong that not even light can escape. Created by the explosion of the most massive stars.

Planetary Nebula

The expanding shell of gas that is escaping a dying, Sun-like (medium mass) star.

Protostar

The piled up mass that has been pulled together by gravity at the center of a nebula. It has not yet undergone nuclear fusion.

Red giant

The stage in the life cycle of a sun-like mass star during which the star increases in size and begins to fuse helium in its core.

White Dwarf

A small, very dense star the size of earth that remains after a middle or low mass star runs out of fuel and is collapsed by gravity.

Red Supergiant

The stage in the life cycle of a massive star during which the star increases in size and begins to fuse helium in its core.

Black Dwarf Star

The remains of a white dwarf star after it has expended all of its energy.gas pressure.

Gas pressure

The outward pressure exerted by gas in a star as it is heated by fusion in the core.

Giant Impact Hypothesis

A mars sized body impacts the early Earth, causing mass to be ejected and re-form into the moon. Sometimes referred to as the "big whack" hypothesis.

Event horizon

The location around a black hole where the escape velocity equals the speed of light; the boundary of a black hole.

Redshift

Shift of light to a longer (redder) wavelength as it moves away; indicates that universe is expanding.

Andromeda Galaxy

Our closest neighboring spiral galaxy, about 2.4 million light years away.

Fermi Paradox

There is a high probability that life exists elsewhere in the universe, but there is also a lack of evidence; where is everybody?

Exoplanet

A planet outside of our Solar System.

Spagettification

The theory that you will become a long, thin stream of atoms, kilometers in length, but narrower than a hair wide when you get pulled into a blackhole.