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47 Cards in this Set

  • Front
  • Back

How does planet formation begin (formation of planetesimals)?

Condensation (gas --> liquid)

** Same as asteroids/meteorites

(Condensation --> accretion --> growth --> differentiation for largest bodies)

What does the word "planet" stand for in Greek?


What led to the discovery of Ceres and Pallas?

Thought there was a missing planet between Mars and Jupiter

How did the name "asteroid" come about?

Herschel coined the term

-Asteroids resemble moving point-like stars (planets appear as full disks)

What led to the discovery of Neptune?

-Discovered by Galileo (not identified as a planet at first)

-Uranus showed small deviations from its orbit that could not be explained by gravity of the sun/all known planets (predicted position of perturbing body --> found Neptune - only planet not found by accident)

What led to the discovery of Pluto?

Search for Planet X (a plant thought to be perturbing Uranus - but was just a poor estimate of Neptunes mass) - found Pluto

What are some properties of Pluto?

-Almost the same size as Charon (its moon)

-Very cold (40K)

-Thin N atmosphere (refreezes onto surface)

-Pluto and Neptune's orbits cross but they're in a 3:2 orbital resonance (never will hit) - pluto has 17 degree tilt with plane of Neptune

Alternative names to asteroid?

- minor planets


Why is pluto and the other asteroids now not called planets?

-Found Eris even farther from Sun and larger (10th planet?) - would be soo many planets if we didn't further define the meaning of planet

What defines a planet?

A celestial body that:

1) orbits the sun

2) sufficient mass for self gravity to make it nearly round/rigid in shape

3) cleared neighborhood around its orbit (pluto failed this criteria)

What defines a dwarf planet?

A celestial body that:

1) orbits the sun

2) sufficient mass for self gravity to make it nearly round/rigid in shape

3) NOT cleared neighborhood around it

4) not a satellite

What defines everything else (other than planets and dwarf planets)?

Small Solar System Bodies (includes asteroids and comets)

How many planets does our solar system have?

8! (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune)

How many dwarf planets are there so far? What are their names?

5 - Eris, Pluto, Haumea, Makemake, Ceres

Asteroids are...

-Are rocky with a wide range of sizes, up to hundreds of kms in diameter

-do not have atmospheres

-most are made of a mix of rocks/metals

-some have their own moons

-we've landed on an asteroid before (Ceres)

Is the asteroid belt densely or loosely packed?

very loosely (million km between them)

How do asteroids and other minor planets get their names?

16 characters or less

-one word prefered



-not too similar to existing names

-can only name ofter political/military activities 100 years after event

Are there more small or large asteroids?

Many small, only few big (total amount of asteroids decreasing in solar system)

If you added up the mass of all the asteroids in the asteroid belt, what object would be closest to this mass?

The moon - actually only 4% of the moon's mass (asteroids are not massive even when added up)

What do asteroids look like?



What is the best way to find the densities of asteroids?

Find an asteroid with a moon and use Kepler's 3rd law (see the asteroid perturbed by gravity of moon)

-Measure asteroid densities by using mass and size

Where are most asteroids found in our solar system?

In the asteroid belt between Mars and Jupiter

Why are there very few asteroids beyond Jupiter's orbit?

Ice could form in the outer solar system

Which explanation for the asteroid belt seems the most plausible?

The belt is where the most asteroids happened to survive

What prevented the planetesimals from accreting into planets between Mar's and Jupiter?

Jupiter's gravity prevented this. (the asteroid belt is not the remains of a destroyed planet)

What are the 3 types of asteroids (S, C, & M-type)?


-silicate (rocky, dominate inner region of belt - 17%)


-carbonaceous (dominate outer region - 75%)


-metal rich (8%)

Define Meteoroid?

Small to boulder sized particle of debris in solar system

Define Meteor?

Bright trail left by a meteoroid that enters Earth's atmosphere (shooting star)

Define Meteorite?

Portion of meteoroid/asteroid that survives its passage through the atmosphere and impact with the ground

Define Meteorology?

atmospheric science

Meteor + Meteorite =

Composition of body in Solar System (meteor track = orbit of the parent body that originates from the asteroid belt)

What are the two types of meteorites?

1) Primitive - unchanged in composition since they first formed (chondrites) - majority

2) Processed - experienced processes like volcanism or differentiation (achondrites) - geologically younger

(subdivide into metal-rich and rock)

* some meteorites are pieces of the Moon and Mars

What is the nucleus of a comet commonly referred to as?

"dirty snowball"

What is a coma?

Atmosphere that comes from heated nucleus of comets

What is a plasma tail?

Gas escaping from the coma of a comet, pushed by solar wind

What is a dust tail?

extension of a comet pushed by photons (comet's tail grows as the comet gets close to the Sun)

Why do meteors in a shower appear to emanate from the same area of the sky?

B/c of Earth's motion through space (meteors appear to converge in a point at a distance)

Most meteors originate from _______, and most meteorites originate from ________.

comets, asteroids (many more comets cross the Earth's orbit, but comet (icy material) does often survive passage through atmosphere (therefore no meteorites)

What is the Oort Cloud?


-Surrounds the solar system

-comets on random orbits/any direction

-spherical distribution

-comets formed closer to the Sun (kicked out by gravitational interactions with jovian planets)

What is the Kuiper belt?

**Kuiper belt is right outside Neptune (outer solar system)


-in ecliptic plane (flat plane) - aligned with planetary orbital plane/same direction of rotation (KBOs orbit like short period comets)

-comets on orderly orbits

-comets formed in Kuiper belt

** essentially failed to become planets

Do cosmic collisions occur?

Yes, asteroids/comets can impact with planets (can see evidence of crater chains on moon and mercury)

About how often is it estimated that an asteroid or comet impacts the Earth with sufficient energy to cause mass extinction?

Once every hundred million years

What is the hypothesized event that lead to the dinosaur extinction?

Impact of Chicxulub crater --> lead to major climate change --> extinction of species

Why don't we detect some incoming asteroids/comets?

If the object comes from the sunlit side of the earth (wasn't bright enough to detect)

What is the relationship between the size and frequency of impacts by asteroids/comets?

Inversely proportional (bigger the object, less frequent the impact)

-small impacts happen almost daily

What are the effects of different impactors based on size?

1) <10m (burns up in atmosphere)

2) 10 -100m (heat/blast for tens of km - nuclear weapon)

3) 100m - 1km (heat/blast over hundreds of km)

4) > 1km (tsunamis, global effects, extinctions)

What are some possible solutions for incoming asteroids?

1) Nuclear weapons

2) Gravity tractor

3) Rocket motor

4) Focused solar energy