Lecture 35 - Dwarf Planets

ASTR 1210 (Exam 3)

Anatomy of a Comet

• Icy snowball will start to melt and sublimate, releasing dust and particles - those dust particles will get swept away by solar wind (charged particles from the sun)

  • Sending them away from the sun 

• Dust tail is slightly impacted by the comet’s motion — still primarily dominated by the sun’s motion

• Coma: atmosphere that comes from a comet’s heated nucleus 

Growth of Tail

• Normally don’t have tails because they’re farther from the sun

Meteor Showers

• Comets are the result of meteor shower - Orionids, Leonids

• Earth is zipping through all those particles of gas and dust that were left behind 

• Seems as if the Earth is zipping in that direction - if you imagine that you were driving in a car and it’s not windy, if you drive through the snowstorm, the snow is zipping by you 

• Meteor showers emanate from the constellation 

• Bigger the comet, the more material it releases —> bigger meteor showers 

Where Do Comets Come From? 

• Deep outer solar system - Oort cloud: random orbits extending to about 50,000 AU

  • Depends on how often they come to the inner solar system

  • Sun perturbed Oort Cloud and sent so much comets to us

  • The ice melted into the water on Earth

• Kuiper Belt: on orderly orbits from 30-100 AU in disk of solar system 

Meteor Terminology 

• Meteorite: 

  • Rock from space that falls through Earth’s atmosphere

• Meteor:

  • Bright trail left by a meteorite

• Meteroid:

  • Rock from space

Meteorite Types

• Primitive: unchanged in composition for 4.6 billion years

• Processed: younger, have experienced processes like volcanism or differentiation

Frequency of Impacts

• Small impacts happen daily

• Depends on size

• Impacts large enough to cause mass extinctions happen many millions of years apart

True or false: A meteorite has never impacted a home around the world within the past 100 years.

False - super rare occurrences

• Smacks into oceans and desolate land masses

Cosmic Collisions

• Comet was gravitationally ripped apart by Jupiter

• Impact and energy that was associated with the collisions - little black spot is the size of the Pacific Ocean

• Huge impact

• Jupiter protects Earth from comets

• First Sun, then Earth

Mass Extinctions

• Some result of natural climate change

• Others catastrophic collisions - dinosaur extinctions 65 million years ago

• Iridium layer around the Earth - commonly found in meteorites and comets

• Collision of a giant rock - layer of iridium

• Found dinosaur fossils below this layer

• After this collision happened, the dinosaurs were unable to survive, get the oxygen, the food they need to, and the energy they need to thrive

Likely Impact Site

• Geologists have found large subsurface crater about 65 million years old in Mexico

Facts About Impacts

• Asteroids and comets have hit Earth

• Major impact is only a matter of time

• 20 meter object in Russia in 2013 - cosmic collision - Russia is huge

Asteroid Deflection Techniques

• Fund the deflection techniques and the science

Exactly how many planets are there in our solar system? 

• Depends on who you ask 

Discovery of Uranus

• William and Caroline Herschel

• Uranus is barely visible to the naked eye with no light pollution

• Direct method for discovery

• Telescopes — very good invention

• New elements discovered - Uranium

The Next Planet

• Giuseppe Piazzi discovered Ceres - between Mars and Jupiter

• Cerium got named

Pallas 

• Palladium

• All in the same region of space

• Planets 10/11 in same region of space

• Found in asteroid belt - more like each other than the planets 

What is a Planet? 

• What is a planet?

• Pluto reclassified as a dwarf planet 

• Plutonium 

• More and more icy bodies - discovered one that was bigger than Pluto - Eris 

• Pluto got demoted to a dwarf planet 

Evolution of the best view of Pluto

• Better images of Pluto

• Explored it because we thought it was a planet

• Haven’t explored other things because of the terms we use to refer to objects

The IAU Defines a Planet

• Planet orbits the sun

• Spherical

• Cleared its neighborhood of orbit - most dominant gravitational member of the neighborhood

• Pluto didn’t pass the third criteria

Language

• More precise we are with our language, the more we can name things