Unit 1: Space and Time 2023 (H)

Andromeda Galaxy

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

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

Black Dwarf Star

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

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.

Cecilia Payne-Gaposchkin

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

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

Conservation of Angular Momentum

The law of physics stating that the total amount of angular momentum in an isolated system remains constant.

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.

Dependent Variable

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

Doppler effect

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

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.

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

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

event horizon

the location around a black hole where the escape velovity equals the speed of light; the boundary of a black hole

exoplanet

A planet outside of our Solar System.

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?

Galaxy

a group of millions, even billions, of stars held together by gravity

Galaxy Cluster

groupings of galaxies that are gravitationally bound and travel through space together

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

Hypothesis

a model/explanation based on observed facts but not yet tested

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.

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.

Jovian Planet

Jupiter-like planets Jupiter, Saturn, Uranus and Neptune

Kuiper Belt

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

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 through space and sometimes our atmosphere

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

Nebula

A large cloud of dust and gas in space

Neutron Star

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

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

Planet

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

Planetary Accretion

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

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.

Proxima Centauri

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

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.

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.

redshift

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

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.

Solar System

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

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

Spiral galaxy

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

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.

Super Nova

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

Terrestrial Planet

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

The Drake Equation

Calculates the probability used to estimate the number of extra-terrestrial civilizations in the solar system

Tunguska

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

Universe

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

Virgo Supercluster

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

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

Walter Alvarez

A scientist who proposed that a large meteorite hit the earth in the Yucatan area of Mexico around 65 million years ago causing the extinction of the dinosaurs

Iridium

An element that is rare on Earth but common in meteorites.

Chixulub

Crater that is located in Yucatán peninsula from asteroid responsible for dinosaur extinction.