What

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What
Is?
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M33, The Pinwheel Galaxy in Triangulum by George
Greaney
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What is Astronomy?
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Basically, if its off this planet its a study of
some realm of astronomy. As one might
imagine that covers an awful lot of subjects,
even more than we know right now. A short list of
subjects include

• NGC 253, galaxy in Sculptor
• by George Greaney

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• Stars
• Nebula
• Planets
• The Sun

• Star clusters
• Galaxies
• Galaxy clusters
• Dark matter
• Black holes

• The Great Andromeda Galaxy
• by George Greaney

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An Astronomer is a Scientist, skilled in
Mathematics, Physics, and Astronomy
Most Professional Astronomers work for
Universities or Government Agencies
Galileo Observatory in Italy
Source The Berkeley Cosmology Group
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Galileo Galilei (1564-1642)
A night watchman with a college education?
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Few astronomers spend much time looking through
a telescope. Most operate telescopes from a
control room or even from their computer at
home via the Internet. Typical astronomers only
spend one or two weeks each year observing, and
the rest of their research time analyzing their
data.
Astronomer Serena Kim at work At Cerro Tololo in
Chili
Source Applied Theoretical and Computational
Physics DivisionLos Alamos National Laboratory
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Amateurs and their tools
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What is an AmateurAstronomer?
Although the Term has different meanings for
different people, a basic definition would
include anyone who looks into the sky, and
wants to see or learn more.
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Tonight You are an Amateur Astronomer
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A Meteor from the annual Leonid Meteor shower
lights the sky
A Meteor is a bright streak across the sky, or a
Shooting star produced when a small piece of
comet or asteroid, called a meteoroid, enters
the Earths atmosphere.
Source The Lowell Observatory
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What is a Meteoroid?
The Giant Asteroid Gaspra
A meteoroid is the dust, rock, or debris still in
space. It could be a chunk of an asteroid or
comet.
Source NASA
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What is a Meteorite?
The Giant Asteroid Gaspra
Meteorite Damage, Peekskill, NY
A meteorite is a meteor that actually falls to
the ground. Most meteors burn up and never make
it to the ground.
Source NASA
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Comet Ikeya Zhang
Image by Dave DockeryAstronomical Society of
Las Cruces
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A comet is basically a ball of ice and dust in
space. The typical comet is less than 10
kilometers across. Most of their time is spent
frozen solid in the outer reaches of our solar
system.
Comet Hale Bopp
Image by Harvard-Smithsonian Center for
Astrophysics
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A comet orbits around the sun, in a wide,
elliptical path. When a comet gets within a few
million miles of the sun, it begins to melt,
leaving a tail of gas and dust that is blown by
solar winds
Comet Hale Bopp
Source NASA
Image by Harvard-Smithsonian Center for
Astrophysics
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Image of the Sun from Goddard Space Flight Center
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What is a Star? Our Sun is the closest star. At
the simplest, a star is just a ball of gas that
has condensed out of interstellar material. The
largest part of its lifetime is spent as a main
sequence star during which hydrogen is being
converted to helium balancing gravitational
contraction so that the radius and energy output
remain almost constant.
Source The British Astronomical Association
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Our Sun is a star that has already spent about 5
billion years on the main sequence.
Scientist believe our Sun is roughly
halfway through it's life.
Source The British Astronomical Association
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Nearby Stars Name Distance from
Earth Sun 93 million miles (8 light minutes)
Proxima Centauri 4.22 Light Years Alpha Centuri
A,B 4.39 Light Years Barnards Star 5.94 Light
Years Wolf 359 7.8 Light Years Lalande 21185
8.3 Light Years Sirius A,B 8.6 Light
Years
Image courtesy of Dave DockeryAstronomical
Society of Las Cruces Source The British
Astronomical Association
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What is a Light Year?
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A Light Year is a unit of Distance, not time. It
is the distance that light travels in one earth
year, which works out to
5,903,300,000,000
Miles
A Light Year is almost six trillion miles long!
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Thats a long way! But even further Than most
folks realize. Compare this to a distant but
familiar object, Like Pluto. Pluto is about 5
light HOURS from Earth. Only a small fraction of
a light year
Pluto, as seen by theHubble Space Telescope
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Omega Centauri
Image by Dave DockeryAstronomical Society of Las
Cruces
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Star Clusters are collections of a few dozen to
many thousands of stars, which are
gravitationally bound.
The Pleiades, an open cluster
Hercules Cluster, a globular cluster
Image by Dirk Langenbach
Image by Dave Dockery
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North American Nebula, Image by George Greaney
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A nebula is a cloud of gas and dust in space.
Some nebulas are regions where new stars are
being formed, others are the remains of dead or
dying stars.
Reflection Nebula IC4592/4601 in Scorpius ,
byGeorge Greaney
Source NASA
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Types of Nebula Emission Nebula
An Emission Nebula absorbs the light of nearby
stars and reaches very high temperatures.
Emission nebula are often found in regions of
space where new stars are forming.
The Orion Nebula Image by Dave DockeryAstronomica
l Society of Las Cruces
SourceNASA
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Types of Nebula Reflection Nebula
A Reflection Nebula is a cloud of gas and dust
which does not create its own light, but
instead shines by reflecting the light from
nearby stars.
The Pleiades Image by Dave DockeryAstronomical
Society of Las Cruces
SourceNASA
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Types of Nebula Planetary Nebula
A planetary nebula is created when a star blows
off its outer layers into space, forming a
nebula In the shape of a ring or bubble
The Dumbell Nebula Image by George Greaney
SourceNASA
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Types of Nebula Absorption Nebula
Dark clouds in space are called absorption
nebulas or dark nebulas. An absorption nebula is
a cloud of gas and dust which blocks light from
the regions of space behind it.
The Horsehead Nebula Image by George Greaney
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The term Nebula was first coined in the 19th
century by Herschell, a famous astronomer, to
distinguish anything in the sky that looked
indistinct. Some of his 'nebulae' turned out to
be entire galaxies such as the Andromeda
Nebula.
The Andromeda Galaxy Image by Dave
DockeryAstronomical Society of Las Cruces
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What is a Black Hole?
Illustration of Cygnus X-1 from the Astronomy Cafe
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What is a Black Hole? Loosely speaking, a
black hole is a region of space that has so much
mass concentrated in it that there is no way for
a nearby object to escape its gravitational pull.
Source The Berkeley Cosmology Group
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What is a Quasar?
Images from Hubble Space Telescope
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What is a Quasar? Quasars are one of the Most
mysterious and rare objects in astronomy A
quasar is a very, Very bright object at the core
of a few highly active galaxies. Quasars are
thought to form as matter spins into super
massive black hole at the center of these
galaxies.
Illustration from the Astronomy Cafe
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The end