Astronomy Exam Study Guide: Key Concepts and Terms

Celestial Bodies

Natural objects in space, such as stars, planets, comets, and asteroids.

Light Year

The distance that light travels in one year, approximately 5.88 trillion miles or 9.46 trillion kilometers.

Black Hole

A region of space having a gravitational field so intense that no matter or radiation can escape from it.

Supernova

A stellar explosion that occurs at the end of a star's life cycle, resulting in a sudden increase in brightness.

Starlike bodies

Another name for asteroids

Size of Asteroids

Range from ~940km to 10km across

Shape of Asteroids

somewhat rounded; mostly odd shaped

What are Earth-Crossing Asteroids?

Asteroids with orbital eccentricities of greater than 0.4 that may intersect Earth's orbit.

What is another name for Earth-Crossing Asteroids?

Apollo asteroids.

Frequency of Asteroid Strikes

Scientists believe that ~3 asteroids strike the Earth every 1 million years

Impact of 100km Asteroid

would hit Earth with a force equal to a million 1-megaton nuclear bombs

Main Asteroid Belt Location

between Mars and Jupiter (2-3 A.U.)

Trojan Asteroids

Orbit at the distance of Jupiter

Kirkwood Gaps

Underpopulated areas of the asteroid belt due to complex gravitational interactions with Jupiter

C-type Asteroids

75% of all asteroids, darkest, least reflective, and contain the most carbon

S-type Asteroids

15% of asteroids, silicate or rocky type, predominate the inner portion of asteroid belt

M-type Asteroids

Metal type, nickel and iron mixes

B-type Asteroids

Rubble pile named after asteroid Bennu

Dawn Mission

Visited Vesta (2011) and Ceres (2015)

OSIRIS-Rex Mission

Studying Asteroid Bennu

Planned Psyche Mission

To explore a metallic asteroid made of iron and nickel

Lucy Mission

Explore Trojan asteroids in Jupiter's orbit

Oumuamua Asteroid

outside of our solar system

Meteoroid

Interplanetary debris smaller than 100m across

Meteor

"Shooting star," bright streak across the sky

Meteorite

Piece of interplanetary debris that reaches the ground

Meteoroid Swarm

Comet material that is dislodged as it orbits the Sun

Micrometeoroids

Very small meteoroids following comet's original orbit

Meteor Shower

Earth passing through the comet's original orbital path

Chicxulub Impact Crater

a 10 km asteroid slammed into the Earth at a 20 - 30 degree angle 64.98 Ma

Tunguska Event

1908, a 30 to 50 m meteorite exploded above ground in Siberia

Comets

Greek for "hair"

Comet Nucleus

A few km sized ball of ice

Comet Tail

Hydrogen envelope that can stretch millions of km across space

Comet Coma

Part of comet that becomes gas and forms a halo around the nucleus

Oort Cloud

Vast reservoir of cometary material 10,000 A.U. across surrounding the solar system

Kuiper Belt

A source of comets located in an elliptical plane beyond Neptune

What is the shape of comet orbits?

elliptical

What happens to a comet's surface when it approaches the Sun?

becomes too warm, and the ice turns from a solid to a gas (sublimates)

What phenomenon is created when a comet's ice sublimates?

A tail

Comet Tails Direction

Always directed away from the Sun due to solar winds

Types of Comet Tails

Straight line ions or diffuse broad dust tails

What is the primary component of comets?

Dust made of silicate minerals

In what type of environment are silicate minerals created?

A warm environment

Where in the solar system are silicate minerals typically found?

Inner

Comet Shoemaker - Levy 9

Discovered in 1993 and found to have been pulled apart by Jupiter; Impacted Jupiter in 1994

What are the characteristics of Jovian planets regarding their distance from the Sun?

Far from Sun

How are the orbits of Jovian planets spaced?

Widely spaced orbits

What is the typical mass and radius of Jovian planets?

Large masses & radii

What is the density of Jovian planets?

Low density

What is the primary composition of Jovian planets?

Predominantly gaseous

Do Jovian planets have a solid surface?

No solid surface

How does the rotation of Jovian planets compare to terrestrial planets?

Faster rotation

What type of magnetic fields do Jovian planets have?

Strong magnetic fields

How many moons do Jovian planets typically have?

Many moons

What do Jovian planets have in addition to moons?

Many rings

What is the largest planet in the solar system?

Jupiter

How many known moons does Jupiter have?

92+ known

What is a notable characteristic of Jupiter's rotation?

rotates rapidly and flattens out at the equator.

How much more massive is Jupiter compared to Earth?

318 times

What type of core does Jupiter have?

A rocky-like core surrounded by 'metallic' hydrogen

What is a distinctive feature of Jupiter's atmosphere?

bands

Great Red Spot

300+ year long hurricane the size of two Earths

Galilean Moons

Io, Europa, Ganymede, Callisto

Io

Active volcanoes, silicate lava, volcanic sulfur plumes

Europa

Icy surface, few impact craters, possible salt water ocean below the icy surface

Ganymede

Largest moon in the solar system

Callisto

Heavily cratered, icy

Saturn

Very high equatorial winds and short-lived storms, rapid rotation, prominent rings made of water ice particles

Titan

Hazy, icy landscape of hydrocarbons, erosion by liquid hydrocarbons and large lakes

Enceladus

Cryo-volcanoes of water

Uranus

Tipped on its side, methane gives planet its blue-green color, very tilted magnetic field

Miranda

Strange fracturing pattern indicates violent past

Neptune

Methane gives planet blue color, has dark rings, very tilted magnetic field

Great Dark Spot

Storm on Neptune discovered in 1989

Triton

Orange tint from nitrogen frost, possible liquid nitrogen geysers

Planetary Status

Must be spherical in shape, orbit the Sun, and clear orbital path

Dwarf Planet

Pluto, neither terrestrial nor Jovian, very inclined orbit, composed mainly of ice

Define Life

React, Grow, Reproduce, Evolve

Drake Equation

Estimates the number of technological, intelligent civilizations now present in our Galaxy

SETI

Search for Extraterrestrial Intelligence

Drake Equation (Formula)

N = R fₚ nₑ f₁ fᵢ f_c * L

Methods for deflecting or destroying an object on a collision course with Earth

Nudging, Blasting, Darkening