Small Bodies in the Solar System ESS ( )

Small Planetary Bodies  In addition to planets & moons, the solar system contains many other types of objects:  including comets,  asteroids, and  meteoroids.  In addition to planets & moons, the solar system contains many other types of objects:  including comets,  asteroids, and  meteoroids.

Comets vs. Asteroids vs. Meteors

Comet Structure  Nucleus  gas and dust are released and form an atmosphere around the comet called the coma  Dust Tail  Usually white  Ion Tail (ionized gas)  Usually blue  Nucleus  gas and dust are released and form an atmosphere around the comet called the coma  Dust Tail  Usually white  Ion Tail (ionized gas)  Usually blue

Comet’s Tail  A comet's tail points away from the Sun due to solar wind  Tail gets longer when it is close to the Sun.  Heat from the Sun melts, actually sublimates the ices from comet is mostly made of.  A comet's tail points away from the Sun due to solar wind  Tail gets longer when it is close to the Sun.  Heat from the Sun melts, actually sublimates the ices from comet is mostly made of.

Comet’s Orbit  Two factors describe orbit  Size of orbit  Long-period > 200 years  From Kuiper Belt or Oort Cloud  Short-period < 200 years  Eccentricity  How “oval shaped”  0 = circle, 1 = very long oval  Halley’s Comet has a high eccentricity  Comet moves faster as orbits sun  Two factors describe orbit  Size of orbit  Long-period > 200 years  From Kuiper Belt or Oort Cloud  Short-period < 200 years  Eccentricity  How “oval shaped”  0 = circle, 1 = very long oval  Halley’s Comet has a high eccentricity  Comet moves faster as orbits sun Halley’s Comet 76 yrs Comet Kahoutek 75,000yrs

Comet’s Orbit  Closest to sun – Perihelion  Furthest from sun - Apihelion  Closest to sun – Perihelion  Furthest from sun - Apihelion

Rosetta Mission

Comet Simulation

Oort Cloud

Where do they come from?

Oort Cloud  Not actually seen  Theoretical explanation  Billions to 2 trillion of objects  Water, ammonia, methane  2000 AU (2000 x distance from sun to Earth)  ~ 1 light year thick  Not actually seen  Theoretical explanation  Billions to 2 trillion of objects  Water, ammonia, methane  2000 AU (2000 x distance from sun to Earth)  ~ 1 light year thick

Asteroid Belt

Asteroids  Size  Meters – 900 km (too small to be planet)  Shape  Irregular  Larger one are more spherical  Content  Lighter – more rock  Darker – more metal  Size  Meters – 900 km (too small to be planet)  Shape  Irregular  Larger one are more spherical  Content  Lighter – more rock  Darker – more metal

Asteroids  Sometimes considered planetoids or minor planets  Most located in asteroid belt (between Mars & Jupiter)  > 200 asteroids larger than 60 miles (100 kilometers) in diameter.  > 750,000 asteroids larger than three-fifths of a mile (1 km) in diameter and  millions of smaller ones.  Sometimes considered planetoids or minor planets  Most located in asteroid belt (between Mars & Jupiter)  > 200 asteroids larger than 60 miles (100 kilometers) in diameter.  > 750,000 asteroids larger than three-fifths of a mile (1 km) in diameter and  millions of smaller ones.

Asteroids  Ceres – largest asteroid in asteroid belt  580 miles across  Considered dwarf planet  Ida – has a natural satellite,  56 km long  Dactyl  1.5 km Dactyl.  Ceres – largest asteroid in asteroid belt  580 miles across  Considered dwarf planet  Ida – has a natural satellite,  56 km long  Dactyl  1.5 km Dactyl.

Asteroids  A large asteroid may have hit the Earth when the dinosaurs were alive –  ~65 million years ago.  A large asteroid may have hit the Earth when the dinosaurs were alive –  ~65 million years ago.

Asteroids  Eventually many will drop out of orbit  maybe from a collision with another asteroid and heads toward Earth.  < 10 km across, will burn up in the atmosphere.  > 10 km across, will hit the surface of the planet.  Hundreds of millions of years ago, collisions with asteroids more often.  Over time, the # of asteroids in the path of the Earth decreased and collisions become less frequent.  Eventually many will drop out of orbit  maybe from a collision with another asteroid and heads toward Earth.  < 10 km across, will burn up in the atmosphere.  > 10 km across, will hit the surface of the planet.  Hundreds of millions of years ago, collisions with asteroids more often.  Over time, the # of asteroids in the path of the Earth decreased and collisions become less frequent.

Meteoroids…  Meteoroid - A small particle from an asteroid or comet orbiting the Sun.  Meteor - A meteoroid that is observed as it burns up in the Earth's atmosphere – a shooting star.  Meteorite - A meteoroid that survives its passage through the Earth's atmosphere and impacts the Earth's surface  Meteoroid - A small particle from an asteroid or comet orbiting the Sun.  Meteor - A meteoroid that is observed as it burns up in the Earth's atmosphere – a shooting star.  Meteorite - A meteoroid that survives its passage through the Earth's atmosphere and impacts the Earth's surface

Meteoroids…  Size  Pebble to boulder (smaller than asteroids)  Shape  Irregular  Content  From asteroids & comets, so likely metal & rock  Size  Pebble to boulder (smaller than asteroids)  Shape  Irregular  Content  From asteroids & comets, so likely metal & rock

Meteor  Heats up to > 2,000˚C.  Creates a streak of light called a “ shooting star ”.  Fireballs - larger meteors -> brighter flash  On average, 1/ 10 minutes, or about 6/hour  Heats up to > 2,000˚C.  Creates a streak of light called a “ shooting star ”.  Fireballs - larger meteors -> brighter flash  On average, 1/ 10 minutes, or about 6/hour

Meteor Showers  Usual rate = 6/hou r  Meteor Shower = rate may be as high as 60/hour  Occur when Earth passes through the tail or debris of a comet  Perseids (mid-August)  Leonids (mid-November)  Usual rate = 6/hou r  Meteor Shower = rate may be as high as 60/hour  Occur when Earth passes through the tail or debris of a comet  Perseids (mid-August)  Leonids (mid-November)

Draconid Meteor Shower

Meteorite  Meteorites could be fragments from collisions involving asteroids.  Most meteorites weigh only a few pounds and cause little damage.  Impact craters  Earth – not many, thick atmosphere  Moon & Mercury – lots, no atmosphere  Where to find –  Antarctica  White & not much snowfall, doesn’t melt  Meteorites could be fragments from collisions involving asteroids.  Most meteorites weigh only a few pounds and cause little damage.  Impact craters  Earth – not many, thick atmosphere  Moon & Mercury – lots, no atmosphere  Where to find –  Antarctica  White & not much snowfall, doesn’t melt

Meteorites  Flagstaff, Arizona  49,000 years ago  Size  Meteorite about 150 feet in diameter  Weighed 650 pounds  Energy = 2.5 million tons of dynamite  Crater  4000 ft wide, 650 ft deep  Flagstaff, Arizona  49,000 years ago  Size  Meteorite about 150 feet in diameter  Weighed 650 pounds  Energy = 2.5 million tons of dynamite  Crater  4000 ft wide, 650 ft deep Barringer Meteorite Crater

Speed (? From yesterday)  Comets  ~ 40 km/s  Asteroids  ~ 25 km/s,  Meteors  11 – 72 km/s  Comets  ~ 40 km/s  Asteroids  ~ 25 km/s,  Meteors  11 – 72 km/s

Our Solar System  Scale Model of Solar System (p. 9)  Read directions  Calculate distances  Color planets  Obtain string/ribbon  Cut out & place planets on string at appropriate distance 1 at a time, (so you don’t lose them!)  clear tape probably best for this.  Scale Model of Solar System (p. 9)  Read directions  Calculate distances  Color planets  Obtain string/ribbon  Cut out & place planets on string at appropriate distance 1 at a time, (so you don’t lose them!)  clear tape probably best for this.