Astronomy Rough Notes - Meteors
BRING:
Meteor samples
DISCLAIMER: These notes do NOT cover everything you need to know. You may need to look up some
item or concept online or in a text. Test questions are not exact copies of the OBJECTIVES but if you
know the OBJECTIVES thoroughly, you should do well on the exams.
HANDOUTS:
None
OBJECTIVES:
Name a planet.
Name a dwarf planet.
What is the major difference between a planet and a dwarf planet?
Where are the dwarf planets in our solar system?
Distinguish between a meteor, a meteorite, and a meteoroid.
What is a "shooting star"? Why do we see it? On average, how big is one?
Why do we study meteorites?
How old is the solar system?
Describe a comet including the nucleus, head and tail. Why do we see a comet?
Roughly, how big are comets?
What is the Oort Cloud? the Kuiper Belt?
Why study comets?
What is a meteor shower? What is the comet connection to a meteor shower?
SOME RESOURCES:
http://www.amnh.org/exhibitions/permanent/meteorites/what/history.php
http://www.meteorite.fr/en/basics/meteoritics.htm
http://www2.jpl.nasa.gov/snc/
http://liftoff.msfc.nasa.gov/academy/space/solarsystem/meteors/Meteorites.html
http://www.amsmeteors.org/showers.html
http://neo.jpl.nasa.gov
http://near.jhuapl.edu
http://ion.eas.asu.edu/Mars/Mars.html
http://epsc.wustl.edu/admin/resources/moon_meteorites.html
http://www.imo.net
What’s out there (in our solar system)? – Sun, Planet, Dwarf Planet, SSSB, Dust
Sun – a star (>99% of mass of solar system)
Two types of planets – Terrestrial and Jovian
Also Dwarf planet that doesn’t fit either of those groups
Planet vs. Dwarf planet
Both orbit a star
Both are round by their own gravity
Planets have cleared smaller objects out of their neighborhood (by colliding with them or ejecting
them)
Comments:
a. 8 planets in our solar system (Mecury, Venus, Earth, Mars, Jupiter, Saturn, Neptune)
b. Over 1500 planets around other stars as of March 2012
See http://science.nasa.gov/astrophysics/focus-areas/exoplanet-exploration/ for some of the
discoveries
c. Historically, Pluto was called a planet (so were Sun, Moon, Ceres at one point)
d. 5 dwarf planets in our solar system (Ceres, Pluto, Haumea, Makemake, Eris)
e. Likely more to be added like Quaoar (Kwah-wahr), Sedna…
See Trans-Neptunian objects http://rst.gsfc.nasa.gov/Sect19/Sect19_2.html
f. More on Dwarf Planets, see
http://www.windows2universe.org/our_solar_system/dwarf_planets/dwarf_planets.html
g. More on Ceres http://www.windows2universe.org/asteroids/ceres.html and
http://hubblesite.org/newscenter/newsdesk/archive/releases/2005/27/image/a
h. More on Pluto http://www.windows2universe.org/pluto/pluto.html and
http://apod.nasa.gov/apod/ap060903.html
i. Historically Ceres was called a planet then an asteroid or minor planet, now a dwarf planet
Ceres video from Dawn mission
http://www.jpl.nasa.gov/video/details.php?id=1392
Small solar system bodies (SSSB) – Basically the smaller bodies in the solar system
Meteoroid – general term meaning rocky, sometimes icy, oblong body in orbit around a star.
Smaller than a dwarf planet
Asteroid –often used meaning large meteoroid
Comet – icy, fuzzy appearance, elliptical orbits with aphelion often beyond Neptune
Dust – small fluff, collection of molecules
Naming/categorization complicated by recent findings such as:
Rocky objects with elliptical orbits like comets but no fuzzy appearance
Rocky objects with elliptical orbits but intermittent fuzz
Objects bigger than Pluto
Many icy objects beyond Neptune
Rocky objects in Jupiter’s orbit
And more
We will return to the Pluto/dwarf planet question later. First look at SSSBs.
Meteoroids/Asteroids
Orbit the sun mostly between Mars and Jupiter (Often called the Asteroid Belt)
Some scattered throughout the solar system
Small (~10m to ~300 mi)
Largest now is Vesta at ~300 mi diameter
Rocky (some may be icy)
Oblong (not spherical) objects - gravity
Examples:
Gaspra http://www2.jpl.nasa.gov/galileo/gaspra.html
Ida and Dactyl http://antwrp.gsfc.nasa.gov/apod/ap990807.html
Eros http://neo.jpl.nasa.gov or http://near.jhuapl.edu
Ceres was classified as one of these until it was upgraded to Dwarf Planet
Meteoroid - Orbiting in space
Meteor - Atmosphere glowing as rock passes through it
- Also called shooting star or falling star
Meteorite - In hand
Meteor (Shooting star, falling star)
Move quickly on the sky (a few seconds)
Small (grain to pea size)
Fast (~ 100 mi/s)
Nearby (~30 to 60 miles)
Collide with Earth’s atmosphere, create bow shock, glow
Most do not reach ground in tact
Add thousands of tons to Earth each year
Fireball
Larger (marble size+)
Basketball size do not totally disintegrate
Types of meteorites
Some recognizable: Iron-Nickel
Some not: Stony
Some a mixture: Stony-iron
Must chemically analyze to determine the relative abundances of the minerals
Where can you be 99% sure that a stone you find comes from the solar system?
Reasons to study them
Composition and origin of the Moon and Mars
http://ion.eas.asu.edu/Mars/Mars.html
http://epsc.wustl.edu/admin/resources/moon_meteorites.html
Origin of the solar system
Age of the solar system (4.6 billion years)
Origin of life??
Murchison meteorite (1969)
ALH84001 - Mars
Possible catastrophes for us? – next time
Samples
Meteor Crater in Winslow, AZ (add to your tourist stop)
Crater: 4/5 mile across, ~500 feet deep
Occurred ~50 000 years ago
Energy ~ 3 Megatons
Original meteor ~ house size
Meteor Shower
Earth sweeps through debris (from comet)
http://www.youtube.com/watch?v=6XTBrYWrey0
Perseids Aug 10-14
Leonids Nov 14-19
Geminids Dec 10-13
Astronomy Rough Notes - Comets
SOME RESOURCES:
http://stardust.jpl.nasa.gov/
http://liftoff.msfc.nasa.gov/academy/universe/comets.html
http://www.noao.edu/noao/comets/comets.html
Look fuzzy with faint tail
http://apod.nasa.gov/apod/ap100617.html or http://apod.nasa.gov/apod/ap091206.html
or http://apod.nasa.gov/apod/image/1601/CatalinaBorrellyArcturus2016-01-01_Hemmerich.jpg
Motion: Moves slowly on the sky (weeks, months). Unlike meteors
Parts of a comet
Nucleus:
Some are frozen, dirty icebergs http://apod.nasa.gov/apod/ap100104.html
Others are loose collections of ice, gas, dust (Comet Shoemaker-Levy 9 in 1993)
http://www2.jpl.nasa.gov/sl9/background.html
Average size: 1 to 10 miles across
Density: 1 – 2 times density of water
Head: Nucleus + gas cloud around the nucleus (gas cloud from heating from sun)
Tail: Trail of gas and dust blown away by the sun wind
Seen because
Nears sun, melts (sublimes), sunlight reflects from debris, (looks dense but is not)
Orbits
Most have elliptical orbits
Some in plane of solar system but some not
Period
Short period like (Halley (76yr), Tempel-Tuttle (33 yr)) – in plane of SS
Long period like (Hale-Bopp (~4000 yr)) – all directions
Orbits and periods suggest two “sources” of comets where comets spend most of their time
Oort Cloud at ~ 100 000 AU (~1 LY)
Kuiper Belt at ~40 AU (Pluto) – ~1000 AU
(These often called Kuiper Belt Objects or KBOs. Sometimes called Trans-Neptunian Objects)
Reminder:
Comets seen for different reason then meteors
Why study comets
Water carriers?
Original material of solar system
Life?
Astronomy Rough Notes - Pluto
~2 times density of water
Inner edge of Kuiper Belt
Distance ~40 AU (Sun ~8 light-min, Pluto ~5 light-hours)
Comet like orbit
Icy
Thin atmosphere that freezes out as Pluto moves farther from sun
Orbit comes inside Neptunes (not for another ~200 years)
3 Moons
100s of other KBOs, some ~ same size as Pluto like Eris, Haumea, Makemake
See also Quaoar (Kwah-wahr) and Sedna
http://science.nasa.gov/headlines/y2004/16mar_sedna.htm?list687798
or Trans Neptunian Objects
http://rst.gsfc.nasa.gov/Sect19/Sect19_2.html
From Ontario Science Center with modifications by Parke
http://www.ontariosciencecentre.ca/scizone/brainz/hamilton/pluto_planet_or_not.asp
Pluto: Planet or Not?
Why Pluto should be considered a planet:
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It has enough gravity to pull itself into a sphere.
It has its own moons.
It’s larger than Haumea and Makemake and most other objects.
It has an atmosphere.
It’s been called a planet since it was discovered in 1930.
Why Pluto shouldn’t be considered a planet:
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It has a much more eccentric and tilted orbit than any of the other planets.
It’s a lot like the comets and other Kuiper Belt objects found at the edge of our solar system.
It’s smaller than four of the planetary moons in our solar system.
It’s smaller than some other KBOs (e.g. Eris)
It has very little in common with Neptune and the other outer planets.
It is most similar to Haumea and Makemake, the latest Dwarf Planets.
False dichotomy
Aren’t there really more than 9 planets in the solar system?
Revised 6 January 2016