Our Planetary Neighborhood and Astronomical Numbers

Flashcards covering key vocabulary related to Our Planetary Neighborhood, Beyond the Solar System, and Astronomical Numbers, including units of measurement and cosmic scales.

Earth

A planet, a body in orbit around a star (the Sun).

Planet

A celestial body in orbit around a star.

Metric system

A system of measurement where units are based on factors of 10.

Sun

A star, a huge ball of gas/plasma, and the primary source of energy in the Solar System.

Star

A huge ball of gas/plasma that generates its own energy, like the Sun.

Solar System

A system of planets, asteroids, comets, and dust held together by the Sun's gravity, all orbiting the Sun on elliptical paths.

Orbit

The elliptical path followed by a celestial body, such as a planet around a star.

Gravity

The fundamental force holding celestial bodies in orbit within the Solar System.

Astronomical Unit (AU)

A convenient measure for planetary distances, equal to the average distance between the Earth and the Sun (149.6 million km).

Light-year (ly)

The distance light travels in one year, approximately 10 trillion km, used as an easy-to-imagine measure of distance for stars.

Proxima Centauri

A star located 4.2 light-years away from Earth.

Milky Way Galaxy

The galaxy that contains our Solar System, spanning more than 100,000 light-years across and containing billions of stars undergoing stellar evolution.

Stellar evolution

The natural process describing how stars are born, age, and die within a galaxy.

Local Group

Our immediate galactic neighborhood, a cluster of around 4 dozen galaxies (including the Milky Way) spanning 3 million light-years across.

Virgo Cluster

A large collection of smaller clusters and groups of galaxies, of which the Local Group is a part.

Supercluster

A collection of larger clusters of galaxies.

Universe

Simply everything; all of space and time and their contents.

Meter (m)

The base unit of length in the metric system.

Gram (g)

The base unit of mass in the metric system.

Centimeter (cm)

A unit of length in the metric system, equal to 10 millimeters or 0.01 meters.

Kilometer (km)

A unit of length in the metric system, equal to 1000 meters.

Milligram (mg)

A unit of mass in the metric system, equal to 0.001 grams.

Kilogram (kg)

A unit of mass in the metric system, equal to 1000 grams.

Scientific notation

A way to write very large or very small numbers using powers of 10, such as 1x10^9 for 1,000,000,000.

Giga (G)

A metric prefix representing 10^9 (one billion).

Mega (M)

A metric prefix representing 10^6 (one million).

Kilo (k)

A metric prefix representing 10^3 (one thousand).

Centi (c)

A metric prefix representing 10^-2 (one hundredth).

Milli (m)

A metric prefix representing 10^-3 (one thousandth).

Micro (µ)

A metric prefix representing 10^-6 (one millionth).

Nano (n)

A metric prefix representing 10^-9 (one billionth).

Look-back time

The concept that the light we see from a distant star left a long time ago, causing us to see what it looked like in the past.

Visible universe (scale)

The observable part of the universe, with an approximate size of 10^26 meters.

Megaparsec (Mpc) (scale)

A unit of distance approximately 10^23 meters, representing the typical size of a galaxy.

Kiloparsec (kpc) (scale)

A unit of distance approximately 10^20 meters.

Parsec (pc) (scale)

A unit of astronomical distance, approximately 10^16 meters, often associated with distances to nearest stars.

Light year (ly) (scale)

A unit of distance approximately 10^15 meters.

AU (scale)

A unit of distance approximately 10^11 meters, representing the Earth-Sun distance.

Radius of Sun (scale)

Approximately 10^8 meters.

Radius of Earth (scale)

Approximately 10^6 meters.

Height of human (scale)

Approximately 100 meters (as an order of magnitude in a sense of scale).

Size of cell (scale)

Approximately 10^-4 meters.

Wavelength of visible light (scale)

Approximately 10^-7 meters.

Size of atom (scale)

Approximately 10^-10 meters.

Size of largest atomic nucleus (uranium) (scale)

Approximately 10^-14 meters.

Size of proton (hydrogen nucleus) (scale)

Approximately 10^-15 meters.