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Unit 1
Space Exploration
• Satellite – any object that orbits around
another object in space
– Natural satellite – any naturally occurring (nonman-made) celestial body in orbit around another
celestial body.
• Examples: moons, planets, asteroids
Scientific Research
• Some satellites are used to gather data for
scientific analysis and can be designed to
perform different types of missions
Communications
• Connect distant places, make communication
possible with remote areas
– Examples: television, telephone, internet
Navigation
• Use radio waves to locate positions
– Example: GPS (Global positioning system): 24
satellites spaced in orbits so that a receiver
anywhere on earth, whether mobile or stationary,
can always receive signals from at least 4 satellites
• GLONASS (Global Orbiting Navigation satellite system) –
satellite navigation system owned by Russia
Meteorology
• Record images of weather systems, show
cloud cover, and monitor hurricanes
• They also carry instruments to measure
temperature, pressure and humidity used in
weather forecasting
Earth Resources
• Help scientists study Earth’s surface
• The satellite’s instruments analyze light and
other radiation reflected and emitted from
surface features
Military
• Gather information about battlefields, take
detailed pictures, locate missing troops and
provide secure communications
The Study of Space
• Space Transportation System (STS) – a
proposed system of reusable manned space
vehicles envisioned by NASA in 1969 to
support extended operations beyond the
Apollo program
• It was replaced with the International Space
Station, with substantial contribution by
Russia
• The ISS was completed in 2010
ISS
ISS
• https://www.nasa.gov/mission_pages/station/
main/index.html
Space Stations
• Allow astronauts to live in space for long
periods of time
• The MIR space station had been staffed
continuously since 1987-2001
• https://history.nasa.gov/SP-4225/mir/mir.htm
MIR
Space Probes
• Car-sized robot craft launched by rockets
• They travel to a predetermined target and
investigate it using their onboard instruments
Types of Space Probes
• Fly-By – surveys its target as it flies past, often
at a distance of several thousand kilometers
– MESSENGER gathered info on Mercury
• Orbiter – travels to a planet or moon then
moves into orbit around it
– Cassini-Huygens gathering info on Titan (a moon
of Saturn)
• Lander – lands on the surface of a moon or
planet (usually start out as orbiters)
– Phoenix Mars Lander
https://www.nasa.gov/missions/current/
Telescopes
• Radio Telescopes
• Computers display radio waves as a digitized
images
• Use a curved dish antenna to gather waves
• Atmosphere does not block out radio waves
• The larger the collector the more clear the
data.
• Used to listen to space
• Example: In 1992, the cosmic Background
Explorer satellite measured ripples in the
cosmic background radiation
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Infrared Telescopes
Infrared radiation is detected as heat.
Is located where the atmosphere is thin:
Mountaintop, airplane, balloon, spacecraft
Detects objects by how much heat is given off
(Can detect stars, extra solar planets, and
comets)
• Used during day or night
• Example: In 1998, the Infrared Space
Observatory discovered water is widespread in
space, from moons to interstellar clouds
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UV, X-ray, and Gamma ray Telescopes
Determine the phase of a star’s life cycle.
Are sent above the Earth’s atmosphere
UV, X-ray, and Gamma rays are absorbed by
Earth’s atmosphere and are difficult to detect
from the ground.
• Example:
• In 1987, the X-ray telescope on the Mir space
station detected X-rays from a supernova.
• In 1990, the Rosat Telescope discovered over
1000 very hot stars that emit extreme
ultraviolet light
• Optical Telescopes
• Functions
– Collect visible light from space
– Form better images of faint and distant stars then
the human eye
• Types
– Refracting Telescopes -Starlight enters and is
refracted (bent) to form a image.
– Reflecting Telescopes - use a mirror to gather light
and bring the image. These telescopes are often
referred to as "Newtonians" because they were
first conceived of by Isaac Newton.
• http://www.herschel.caltech.edu/
Origin of the Universe
• Two Theories:
• 1. The Steady State Theory
• 2. The Big Bang Theory
Steady State Theory
• 1948 – Thomas Gold
• the universe has always been pretty much the
same as it is today and will always stay the
same
• suggests that the universe is the same
everywhere and time is also the same
everywhere
• Gold claimed that the universe should look
the same in all places and at all times past,
present, and future (basically nothing is
moving or changing
The Problem
• In 1929, Edwin Hubble had discovered that all
matter in space is moving away from all other
matter. This means that the universe is
expanding
• Gold explained this by saying that as matter in
space is moving apart, new matter is being
created to fill in the gaps. (However, this is
not very likely.)
The Steady State Theory is Ruled Out
• The most important piece of evidence against
the Steady State theory comes from NASA.
• A satellite called the Cosmic Background
Explorer (COBE) looked 15 billion light years
into space (which is the same thing as looking
15 billion years into the past).
• COBE found temperature differences that
indicating that the universe has changed over
time.
Big Bang Theory
• In the late 1920s, George-Henri Lemaitre (a
Jesuit priest) used information from Einstein
and others to formulate the Big Bang
theory.
• Scientists originally did not like the Big Bang
theory because it proposed a “moment of
creation” that seemed to lean towards
religious views of creation
• The Big Bang Theory states that 15-20
billion years ago the universe began as an
infinitely dense “atom” and all matter
everywhere was contained in this “atom.”
The “atom” exploded,– hence, the big bang
A make-believe timetable of the big
bang:
Within the first second after the Big
Bang gravity came into existence
The universe then expanded rapidly
and became flooded with subatomic
particles that slammed into one
another, forming protons and
neutrons.
Three minutes later, the temperature
was 500 billion degrees Fahrenheit.
Protons and neutrons formed the
nuclei of the simplest elements
hydrogen, helium, and lithium.
300 million years later, stars and
galaxies began to appear (such as our
galaxy, the Milky Way).
• Approximately 15.5 – 10.5 billion years after the Big
Bang (4.5 billion years ago), our sun and planets
formed from a solar nebular (cloud of gas and dust).
As the nebula condensed, the temperature in its core
got hot enough for nuclear fusion to occur. The core
became the sun and the bodies farther from the core
became the planets
Evidence
• Traces of background radiation can still be
detected with radio telescopes
• Proof that the universe is expanding was
found when Edwin Hubble traced light from
stars in other galaxies and found that matter
in space is clearly moving away from other
matter
• Everything in the universe is still moving away
from other matter, even today
• It is hard to sense that we are still moving
because everything is still moving too. It is
sort of like being in an exploding firecracker.
• How does the Big Bang Theory explain the
concept of linear time?
• Stephen Hawking wondered whether the
universe has any beginning at all in terms of
space or time.
• He suggested that in the earliest stages of the
universe, linear time (the orderly progression
from past to future) did not exist.
• He proposed that time, like the Earth, may be
a circle.
• “Asking what happened before the Big Bang is
like asking for a point one mile north of the
North Pole.”
Other Objects in the Solar System
Asteroids: Rocks that orbit the sun, mainly in
the asteroid belt between Mars and Jupiter.
However, there are some Earth-crossing
asteroids. These asteroids are called Near Earth
Asteroids (NEAs).
How have asteroids affected Earth?
• One widely accepted theory blames an
asteroid impact for the extinction of the
dinosaurs about 65 million years ago. The
impact caused a massive dust cloud that killed
many plant species essential to the dinosaurs’
survival.
Meteoroids, Meteors, and Meteorites
• Meteoroids: Asteroids caught by Earth’s
atmosphere.
• Meteors: Meteoroids that burn up in Earth’s
atmosphere. These are commonly referred to
as “shooting stars.” Meteors are streaks of
light in the sky resulting from the heat
generated by the friction of an incoming
meteoroid as it passes through the Earth’s
atmosphere.
• Meteorites: Meteoroids that fall to Earth
without burning up and actually strike the
surface of the Earth.
Comets
• Comet: Masses of ice, dust, and rock
particles that orbit the sun.
• Tail: The tail of a comet is not a permanent
part of the comet; it forms only when the
comet nears the sun. The tail becomes visible
when the ice inside the comet is heated by the
sun, sublimates (goes from a solid to a gas),
and is given off as a dust filled gas. No matter
which direction a comet is traveling, its tail
always points away from the sun.
• Head (Coma): The head forms at the same time as
the tail by the same process.
• Nucleus (Center): The solid, permanent part of a
comet
Where Are Comets Found?
• Comets are found in the Oort Cloud and
Kuiper Belt (named after the astronomers who
discovered them). Both the Kuiper Belt and
the Oort Cloud are located outside our solar
system, therefore we do not see the majority
of comets, but they are still bound to the sun’s
gravitational force
• The Kuiper Belt extends from the orbit of
Neptune out to several thousand astronomical
units (AUs) beyond (remember, 1 AU = 150
million km or 93 million miles). Comets in the
Kuiper belt orbit the sun peacefully unless
some gravitational influence sends one into an
orbit that takes it outside of the belt
• The Oort Cloud extends beyond the Kuiper
Belt, farther away from the sun. Comets in
the Oort Cloud may change their path to the
inner solar system only if the gravitational
field of something else acts upon it
Famous Comets
• Halley’s comet - the orbit of Halley’s comet
comes close to Earth approximately every 86
years and is due back in 2062
• Shoemaker-Levy 9 comet - the ShoemakerLevy 9 comet collided with Jupiter in 1994
What happens when comets get really
close to the sun?
• When a comet makes its nearest approach to
the sun, some pieces break off from the
nucleus, forming micrometeoroids and we
experience a meteor shower
Why do scientists believe that our
solar system is 4.6 billion years old?
• They use the process of radioactive decay to
date objects in our solar system. Radioactive
decay is the natural process by which a
specific atom or isotope is converted into
another specific atom or isotope at a constant
and known rate. By measuring the effects of
radioactive decay in a given sample (such as a
meteorite), it is possible to determining the
age of the sample.