Meteors, Asteroids, & Comets (Power Point 10) Comet Lovejoy 2015 Image Credit: Sky & Telescope

Student Learning Objectives Construct a model of the Solar System; its creation, contents, and evolution. Classify & describe meteors, meteoroids, and meteorites Differentiate between meteors, asteroids, and comets Identify the locations of groups of small objects in our solar system

What is the origin of meteors? Meteors are bits of matter that have two possible origins. Asteroid Collisions (bits of rock are ejected) Single Meteor Comet trails (bits of comet along path) Meteor Shower Image Credit: NASA

Meteor Photo from ISS Image Credit: NASA

Classifying Rocky Debris Object Location Description Meteoroid Space Orbit Sun Meteor Earth’s Atmosphere “Shooting Star” Meteorite Earth’s Surface Impact Earth (2/year)

“Falling Stars” Meteors are fast! (22,000 - 89,000 mph) KE is huge! Meteors heat up in the Earth’s atmosphere (bright)

Practice What quantity causes the KE of a meteor to be “huge”, mass or speed? Explain why meteors heat up in the atmosphere? What is the primary difference between a meteoroid, meteor, and meteorite?

Meteor Showers When Earth passes through dust particles left behind by a comet, there is a meteor shower. The dust particles enter Earth’s atmosphere from the same direction (radiant). http://stardate.org/nightsky/meteors Image Credit: NASA

Meteor Shower Radiant Image Credit: NASA

Image Credit: NASA

Practice What is the correct name for a “falling star”? What is the probability of being hit by an object falling from the sky? http://geology.com/meteor-impact-craters.shtml http://szyzyg.arm.ac.uk/~spm/neo_map.html

K-T Event Sixty-five million years ago, about 70% of all species disappeared within a very short period. This was called the Cretaceous-Tertiary Mass Extinction, or K-T Event. Many theorize that this was the result of a giant impact.

What are the locations of asteroid groups? Asteroids are leftover rocky planetesimals. Most asteroids are located in the main asteroid belt between 2.3 and 3.3 AU. Irregular shapes Many sizes Rotations 3-20 hours Some binary systems Some differentiated Image Credit: NASA

Image Credit: NASA

3 asteroid orbits/1 Jupiter orbit (3:1)

Reason for Kirkwood Gaps The gaps result from orbital resonances with Jupiter. These gaps have been cleared of asteroids by Jupiter’s dominant gravitational influence.

Practice Characterize the objects in the asteroid belt. Compare and contrast asteroids to planets in our solar system. What is required for a gap in the asteroid belt to occur?

Apollo Asteroids Apollo asteroids orbit within the inner solar system, crossing Earth’s orbit. Impact Earth (1/250,000 years) Image Credit: COSMOS

Trojan Asteroids Trojan asteroids are located on Jupiter’s orbit. One group ahead One group behind https://www.exploremars.org/trojan-asteroids-around-jupiter-explained Image Credit: Facweb

Artist’s conception of Trojan Asteroids Image Credit: JPL/NASA

Practice What is the origin of a single meteor? What is the origin of a meteor shower? Why are asteroids irregularly shaped, not spherical like planets? Meteorites are found with different compositions. Why? What process could explain this?

What is the structure of a comet? Comets are leftover icy planetesimals. Mostly ices NH3 CH4 CO2 H2O Some silicates The nucleus is an irregularly shaped solid ball of ices with dust grains. The coma is a sphere of tenuous gas and dust that surrounds the nucleus. (Ices vaporize)

Comet Halley's Nucleus APOD 2010 January 4

The coma stretches into two tails.   Gas tail points away from Sun (ionized gasses) Dust tail follows orbit of comet http://www.st-andrews.ac.uk/~bds2/ltsn/ljm/JAVA/COMETORB/COMET.HTM

Animation by Dakota Dillard https://www.youtube.com/watch?v=38jYN5OkbBc Animation by Dakota Dillard

Three Month Composite of Comet Holmes APOD 2008 February 5

Location of Comets Beyond Neptune Kuiper Belt (30-55 AU) Oort Cloud (5,000-100,000 AU) Distant enough that a passing star can alter the orbit

Image Credit: NASA

Practice Which tail is typically seen with your eyes? Does a comet always have a tail? Not all comets return to the inner solar system. What are the possible reasons for this? Have we ever landed on a comet?

Animation by European Space Agency (ESA) https://www.youtube.com/watch?v=iEQuE5N3rwQ Animation by European Space Agency (ESA)