Vagabonds of the Solar System

Chapter 6Pages 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” SizePluto 1930 Kuiper Belt (TNO) 248 yrs 2380 km

Ceres 1801 Asteroid belt 4.6 yrs 940 kmEris 2003 Kuiper Belt (TNO) 557 2400 km

Makemake 2005 Kuiper Belt (TNO) 310 yrs 800 km

Haumea 2004 Kuiper Belt (TNO) 285 yrs 2000 km

Ceres

Asteroid Belt • 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

– 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

• 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