Transcript Linking Asteroids and Meteorites through Reflectance

Introduction to Physical Science
Monday, Wednesday, Thursday
Tom Burbine
[email protected]
Schedule
• December 8 • December 9 – Presentations
– 5-10 minutes
– On how you would teach something you learned in class to your
students
• December 13 – Final
– Covers everything from midterm
– Can bring in one sheet of paper with anything you wanted written on it
– Also, your mineral identification sheets
Unit of distance in Astronomy
• A light-year is the distance that light travels in a year
• 10,000,000,000,000,000 meters
• 5,878,625,373,184 miles
Life of a Star
• A star-forming cloud is called a molecular cloud
because low temperatures allow Hydrogen to
form Hydrogen molecules (H2)
• Temperatures like 10-50 K
Region is approximately 50 light years across
Condensing
• Molecular clouds tends to be lumpy
• These lumps tend to condense into stars
• That is why stars tend to be found in clusters
Protostar
• The dense cloud fragment gets hotter as it
contracts
• The cloud becomes denser and radiation cannot
escape
• The thermal pressure and gas temperature start to
rise and rise
• The dense cloud fragment becomes a protostar
When does a protostar become a star
• When the core temperatures reaches 10 million K,
hydrogen fusion can start occurring
Classification of Stars
• Stars are classified according to luminosity and
surface temperature
• Luminosity is the amount of power it radiates into
space
• Surface temperature is the temperature of the
surface
Hertzsprung-Russell Diagram
• Ejnar Hertzsprung and Henry Norris Russell
plotted spectral type (temperature) versus stellar
luminosity
• Saw trends in the plots
• Stars did not plot randomly
OBAFGKM
• Oh Be A Fine Girl/Gal Kiss Me
• http://www.mtholyoke.edu/courses/tburbine/ASTR223/O
BAFGKM.mp3
Hertzsprung-Russell Diagram
• Most stars fall along the main sequence
• Stars at the top above the main sequence are
called Supergiants
• Stars between the Supergiants and main sequence
are called Giants
• Stars below the Main Sequence are called White
Dwarfs
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white dwarfs
• giant – a star with a radius between 10 and 100
times that of the Sun
• dwarf – any star with a radius comparable to, or
smaller than, that of the Sun
Classifications
• Sun is a G2 V
• Betelgeuse is a M2 I
Main Sequence Stars
• Fuse Hydrogen into Helium for energy
• On main sequence, mass tends to decrease with
decreasing temperature
Things to remember
• 90% of classified stars are on main sequence
• Main sequence stars are “young” stars
• If a star is leaving the main sequence, it is at the
end of its lifespan of burning hydrogen into
helium
Stellar Classifications
• O, B, A, F, G, K, M
• A0, A1, A2, … A9 in the order from the hottest to
the coolest
“Deaths” of Stars
• White Dwarfs
• Neutron Stars
• Black Holes
White Dwarfs
• White Dwarfs is the core left over when a star can
no longer undergo fusion
• Most white dwarfs are composed of carbon and
oxygen
• Very dense
– Some have densities of 3 million grams per cubic
centimeter
– A teaspoon of a white dwarf would weigh as much as
an elephant
White Dwarfs
• Some white dwarfs have the same mass as the
Sun but slightly bigger than the Earth
• 200,000 times as dense as the earth
White Dwarfs
• Collapsing due to gravity
• The collapse is stopped by electron degeneracy
pressure
Electron Degeneracy Pressure
• No two electrons can occupy the same quantum
state
The Sun
• Will end up as a White Dwarf
Neutron Star
•
•
•
•
Neutron stars are usually 10 kilometers across
But more massive than the Sun
Made almost entirely of neutrons
Electrons and protons have fused together
How do you make a neutron star?
• Remnant of a Supernova
Supernova
• A supernova is a stellar explosion.
• Supernovae are extremely luminous and cause a
burst of radiation that often briefly outshines an
entire galaxy, before fading from view over
several weeks or months.
• The last person to see and chronicle a supernova
outburst in our galaxy was Johannes Kepler.
• That was in 1604 rivaled Venus in brightness.
Density
• You could take everybody on Earth and cram
them into a volume the size of sugar cube
Explosion
• The collapse of the core releases a huge amount
of energy since the rest of the star collapses and
then bounces off the neutron core
• 1044-46 Joules
• Annual energy generation of Sun is 1034 Joules
Black Hole
• After a supernova if all the outer mass of the star
is not blown off
• The mass falls back on the neutron star
• The gravity causes the neutron star to keep
contracting
Black Hole
• A black hole is a region where nothing can
escape, even light.
Event Horizon
• Event Horizon is the boundary between the inside
and outside of the Black Hole
• Within the Event Horizon, the escape velocity is
greater than the speed of light
• Nothing can escape once it enters the Event
Horizon
http://www.astronomynotes.com/evolutn/remnants.gif
Can you see a Black Hole?
No
• Black Holes do not emit any light
• So you must see them indirectly
• You need to see the effects of their gravity
Any Questions?