Transcript Vagabonds of the Universe

Vagabonds of the Solar System
Chapter 6
Pages 203-231
Appendix F
Vagabonds???
• Vagabond- a person with out a fixed home
who moves from place to place and has no
apparent means of support, wander…
• These objects do have fixed homes….
Overview (P203-204)
• Types of Objects
– Asteroids – rock and metal
– Meteoroids – small asteroids
– Comets- mostly ice and rock
– Dwarf planets
• Locations
– Asteroid belt between Mars and Jupiter
– Kuiper belt – beyond Neptune
– Oort Cloud
Definitions
• Planet- a celestial body
– 1. Orbits the sun
– 2. Sufficient mass to form a sphere
– 3. Cleared its neighborhood of other debris
• Moon- a celestial object in orbit around a
planet.
• Dwarf Planet
– Satisifies 1 and 2 but not 3
• SSSB- small solar system bodies
– everything else
Pluto
• Archetype of plutoids
• Discovered in 1930 by Clyde Tombaugh
• Orbit
– Eccentricity = 0.25 largest in solar system
(Mercury = .21) sometimes closer to sun than
Neptune
– Extreme Orbit tilt to ecliptic
• Size- 2380km
Other Dwarf Planets
Name
Location
“Year” Size
Pluto
1930 Kuiper Belt (TNO)
248 yrs
2380 km
Ceres
Eris
1801 Asteroid belt
2003 Kuiper Belt (TNO)
4.6 yrs
557
940 km
2400 km
Makemake 2005 Kuiper Belt (TNO)
310 yrs
800 km
Haumea
285 yrs
2000 km
2004 Kuiper Belt (TNO)
Ceres
Asteroid Belt
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Ceres- 1801 by Sicilian Giuseppe Piazzi
Pallas- 1802 German Heinrich Olbers
Juno and Vesta – early 1800’s
Prior to 1891 – 300 asteroids discovered
German Max Wolf developed photographic
technique
• September 2008:
– 189,407 confirmed
– 51,272,383 awaiting confirmation
• All the asteroids together would not make a planet
Categories of Asteroids
• Trojan Asteroids
– Captured by Jupiter, 60o behind and ahead
– Any planet can have “trojan” asteroids
– Earth 2010
• Amor Asteroids
– Cross Mar’s orbit but do not cross Earth’s orbit
• Apollo Asteroids - 5525
– Cross Earth’s Orbit
– At least 1038 may strike earth someday
– Icarus Asteroids come closer to sun than Mercury
Comets
Page 213-223
Dirty Snowballs
• Frozen water
• Rock and metal
• Ices of other compounds
– carbon dioxide
– methane
– ammonia
• Formed near Saturn, Uranus, Neptune
– first few hundred million years of solar system
• Gravity of Neptune and Uranus “flung” in all
directions.
Locations (Kuiper Belt)
• Kuiper Belt
– Neptune (30AU- 2.8 trillion miles) out to 50 AU 4.7 trillion miles from Sun
– Centered on the plane of the ecliptic
– Two types
• Classic KBO’s – roughly circular orbits
• Scattered KBO- elliptical orbits (35AU to 200AU)
– Number
• 1471 observed – 10 km +
• 1015 estimate objects of all sizes
Location (Oort Comet Cloud)
• Spherical distribution around sun
• 50,000 AU- 1/5 distance to nearest star
4.65X1012 miles
• Most have circular orbits that keep them far
from the sun
• Sedna – Highly elliptical orbit may take it into
the Oort Cloud region or may be a KBO
Overview (P203-204)
• Types of Objects
– Asteroids – rock and metal
– Meteoroids – small asteroids
– Comets- mostly ice and rock
– Dwarf planets
• Locations
– Asteroid belt between Mars and Jupiter
– Kuiper belt – beyond Neptune
– Oort Cloud
Wayward Comets
• Natural home is far from earth and sun
• Orbits near earth and sun
– Collisions with other objects
– Gravitational pull of passing star
• Orbits
– Highly elliptical, parabolic, hyperbolic
– Period – short period, long period, sun grazing,
planet smashing
Structure of a Comet
• Far from the sun – completely frozen
– Nuclei (singular nucleus)
– 1 to +10km (Comet Halley, Halley’s Comet 15 km)
• Close to the sun – 20 AU about Uranus orbit
– Solar radiation vaporizes ice on the surface
– coma – gaseous atmosphere of a comet- fuzzy
luminous ball
– largest was 1 million km across
– unseen hydrogen envelope
Tails of a comet
• Long, flowing diaphanous (gauzy, transparent)
• Coma gas and dust pushed outward by radiation
and particles from the sun
• Tails always points away from the sun
• Gaseous tail (ion or plasma)
– relatively straight
– Blue
• Dust tail
– White
– Arches in between gas tail and direction of motion
Comet Halley
Comet West
Comet Wild - aerogel
Comet Dust Particle
Comet Hale-Bopp 1997
Meteoroids, Meteors, Meteorites
Page 224-231
Definitions
• Meteoroids- rocky and metallic debris
– smaller than asteroids
– scattered throughout the solar system
– No more than 10m across
– Some smaller than 1 mm
– Chunks knocked off asteroids
• Meteors- meteoroids burning up in the
atmosphere
– -shooting stars, fireballs, bolides
• Meteorites- remnants of meteors that land
intact.
Meteor Showers
• Occur when Earth passes through the orbit of
debris left behind when a comet broke up
• 30 different showers each year
• Named for the constellation from which the
meteors appear to radiate
• > 1 per minute
• Best viewed after midnight
Meteorites
• Most meteors burn up in the atmosphere so
relatively few meteorites.
• Tell us about the solar system
• Increasing Earth mass by 300 ton per day
• Sometimes large craters
– Can be very destructive
Types of Meteorites
• Metal Meteorites
– Important constituent of asteroids and meteoroids
– Nickel-iron crystals formed when molten metal cools
slowly over many millions of years
• Stony –Iron Meteorites
– Fusion crust due to heating
• Carbonaceous chondrites
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Contain small glass-rich beads
Contain complex carbon compounds
No evidence of having been melted as part of asteroids
Ergo- may be primordial material form which the solar
system formed
Iron (Metal) Meteorite
Stony Meteorite
Stony-Iron Meteorite
Carbonaceous Chondrite
Carbonaceous Chondrite
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Dark gray
Complex carbon compounds
20% water
Have not experienced significant heating
• Not from asteroids
• Primordial material from the creation of the
solar system.
Tunguska Event
• 1908 in Siberia, investigated in 1927
• Millions of tons of dust into the atmosphere
• Trees seared and felled radially 30 km
diameter (upright at center)
• No crater
• Explosion of an asteroid 80 meters (260ft) in
diameter at 79,000 km/h (50,000 mph) in the
atmosphere above the site.
• Shock wave slammed into the ground
• – no crater.
Mass Extinctions
• 65 million years ago
– Thin iridium-rich layer
– Coincident with dinosaurs
– Perhaps indicating dust from a meteorite strike
• 250 million years ago
– “Great Dying”- 80-90% of species extinct
– Rocks containing fullerenes – carbon compounds
– impact site discovered in 2004