Transcript Objects in Space

Orbits & Objects in Space
What is an orbit?
• An orbit is a regular, repeating path that one
object in space takes around another one. An
object in an orbit is called a satellite. A
satellite can be natural, like the Earth or the
Moon. It can also be man-made, like the Space
Shuttle or the ISS.—NASA
Satellites
• A satellite is actually trying to travel in a
straight line to conform to Newton's 1st
law of motion (an object will remain at rest
or in uniform motion in a straight line
unless acted upon by an external force).
• However, the Earth's gravity is, at the same
time, pulling the satellite down (the
external force in Newton's law).
Satellites and Orbits
• Imagine a firing a gun horizontally.
• The bullet will eventually fall to Earth. But
what if the bullet were travelling fast
enough that it passed the horizon before
starting to drop?
• As the bullet fell to Earth, the curvature of
the Earth would mean the ground was
curving away underneath it.
Satellites and Orbits
• Now, apply that to a satellite. If the satellite
is travelling fast enough, the curvature of
the Earth will cause the ground to fall away
from beneath the satellite as gravity is
pulling it down. This process continues,
causing the satellite to orbit the Earth.
Orbits and Forces
LEO
Path of Satellite
Low Earth Orbit (LEO):
Orbiting at an altitude of
600-1,000 km.
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Types of Earth Orbits
• LEO (Low Earth
Orbit)
• ~520-1,500 km
altitude
• Orbital period
~ninety minutes
MEO (Medium Earth Orbit)
•~20,000 km altitude
•Between LEO and GEO
•Orbital period ~5-6
hours
Types of Earth Orbits
GEO (Geosynchronous or
Geostationary Earth Orbit)
•~36,000 km altitude
•Orbital period ~24
hours (matches Earth’s
rotation)
HEO (High Earth Orbit or
Highly Elliptical Orbit)
•~40,000 km altitude (at
perigee)
•Large dwell time over
one hemisphere
•Orbital period ~12-24
hours
Planetary Orbits
How do the planets stay in orbit around the sun?
• The solar system was formed from a rotating
cloud of gas and dust which spun around a
newly forming star, our sun, at its center.
• The planets all formed from this spinning diskshaped cloud, and continued this rotating course
around the sun after they were formed.
Planetary Orbits
• The gravity of the sun attracts the planets and
keeps the planets in their orbits. The stay in their
orbits because there is no other force in the solar
system which can stop them.
• In fact, the planets are constantly falling toward
the sun in much the same way that a thrown ball
falls down to the ground.
Planetary Orbits
• When you throw a ball. it moves away from you
and falls to the ground.
• If you throw the ball slowly, it lands on the
ground a few feet from you.
• If you throw it faster, it will fall farther away.
• The faster you throw the ball, the farther it goes.
Planetary Orbits
• Now imagine throwing the ball so fast that its
path has the same shape as the curvature of the
Earth.
• Since the Earth is round, the ball you threw would
fall all the way around the planet.
• If it goes fast enough to keep going around and
around, the ball would stay in orbit. The planets
stay in orbit around the sun in the same way.
Our Solar System
Our solar system is made up
of:
• Sun
• Eight planets (Poor Pluto )
• Their moons
• Asteroids
• Comets
Planets
A "planet” is a celestial body that:
– (1) is in orbit around the Sun,
– (2) has sufficient mass for its gravity to assume
a nearly round shape
– (3) has “cleared the neighborhood” around its
orbit.
• it has enough gravity that it does not share its orbit
space with any other similarly sized body other than
its own moons. (Pluto shares its orbit so it’s now a
dwarf planet)
Inner Planets
The inner four rocky
planets at the center of
the solar system are:
• Mercury
• Venus
• Earth
• Mars
Outer Planets
The outer planets composed
of gas are :
• Jupiter
• Saturn
• Uranus
• Neptune
Comets
• The word "comet" comes from the Greek
word for "hair.”
• Our ancestors thought comets were stars
with what looked like flowing hair trailing
behind.
Comets: “Dirty Snowballs”
• Comets are loose collections of ice, dust,
and small rocky particles whose orbits are
usually very long, narrow ellipses.
Structure of a Comet
A Comet’s Head
– Outer layer= Coma (water vapor,
CO2, and other gases)
– Solid inner core= Nucleus (frozen
ice, gas and dust )
Comet’s Tail
• As a comet approaches the sun and heats
up, some of its gas and dust stream outward,
forming a tail.
• Most comets have 2 tails:
– gas (ion), tail
– dust tail
• Tails point away from the sun because of
the force of the solar wind.
• A comet’s tail can be more than 100 million
kilometers long.
Comet’s Tail
Comet’s Orbit
• Comets move in an elliptical shaped orbit.
Origin of Comets
• Most comets are found in 2 regions of the
solar system: Kuiper belt and Oort cloud.
• Kuiper belt-doughnut-shaped region that
extends beyond Neptune’s orbit to about
100 times Earth’s distance from the sun.
– populated with frozen bodies left over from the
solar system's formation
• Oort cloud-spherical region of comets that
surrounds the solar system out to more than
1,000 times the distance between Pluto and
the sun.
Famous Comets
• Comet Halley is perhaps the most famous comet in history.
• Each time this comet's orbit approaches the Sun, its 15-km
(9-mile) nucleus sheds about 6 m (7 yards) of ice and rock
into space. This debris forms an orbiting trail that, when
falling to Earth, is called the Orionids meteor shower.
• Halley’s comet reappears every 76 years. Its next
appearance is in 2061.
Comet Hale-Bopp
• July 23, 1995- an
unusually large and bright
comet was seen outside of
Jupiter's orbit by Alan
Hale of New Mexico and
Thomas Bopp of Arizona.
• Exceptionally large size.
• It was visible even
through bright city skies,
and may have been the
most viewed comet in
recorded history.
• It will not appear again for
another 2,400 years.
Other Famous Comets
• Comet Hyakutake-On January 30, 1996, Yuji Hyakutake
(pronounced "hyah-koo-tah-kay"), an amateur astronomer
from southern Japan, discovered a new comet using a pair
of binoculars.
• Comet Shoemaker-Levy 9-Between July 16 and July 22,
1994, more than 20 fragments of Comet Shoemaker-Levy
9 collided with the planet Jupiter. Astronomers Carolyn
and Eugene Shoemaker and David Levy discovered the
comet in 1993. It was the first collision of two Solar
System bodies ever to be recorded.
Asteroids
• A small and rocky space object that orbits the
sun.
• Most asteroids are found in the asteroid belt.
• The asteroid belt is located between the orbits
of Mars and Jupiter.
• Also called a “minor planet” or “planetoid”
• Smaller than planets but larger than
meteoroids
How many asteroids are there?
• There are about 40,000 known asteroids that are
over 0.5 miles (1 km) in diameter in the asteroid
belt About 3,000 asteroids have been cataloged.
• There are many smaller asteroids (100,000).
• Asteroids are made of metals, silicate, iron, nickel,
and carbon.
• The first one discovered (and the biggest) is
named Ceres; it was discovered in 1801.
• Asteroids range in size from tiny pebbles to about
578 miles (930 kilometers) in diameter (Ceres).
ASTEROIDS BECOMING MOONS
• Asteroids can be pulled out of their solar
orbit by the gravitational pull of a planet.
They would then orbit that planet instead of
orbiting the Sun.
• Astronomers theorize that the two moons of
Mars, Phobos and Deimos, are captured
asteroids.
Asteroid Strike
• Scientists hypothesize that one or more
large asteroids hit Earth 65 million years
ago and caused extinction of the dinosaurs.
• Scientists also hypothesize that the largest
mass extinction, 250 million years ago,
killing off 90% of all species was also
caused by a large asteroid.
Meteoroids
• Meteoroid-chunk of rock or dust in space.
• Meteoroids come from comets or asteroids
• Smaller than an asteroid.
Meteor
• When a meteoroid enters Earth’s
atmosphere, friction with the air creates heat
and produces a streak of light that you can
see in the sky.
• A meteor is a meteoroid that enters Earth’s
atmosphere and burns up.
Meteorites
• Meteoroids that pass through the
atmosphere and hit Earth’s surface are
called meteorites.
• Classified by composition: stony, iron ,or
stony-iron.
What do we do if an NEO
(Near-Earth-Object) is approaching?
• Unknown… Still being experimented.
• Scientist are calculating ways to use nuclear
energy to divert an incoming object.
• High energy x-ray pulses produce a shock
wave to push the NEO in the opposite
direction.
Review
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Comet: A comet is a relatively small solar system body that orbits the
Sun. When close enough to the Sun they display a visible coma (a fuzzy
outline or atmosphere due to solar radiation) and sometimes a tail.
Asteroids: are small solar system bodies that orbit the Sun. Made of rock
and metal, they can also contain organic compounds. Asteroids are similar
to comets but do not have a visible coma (fuzzy outline and tail) like
comets do.
Meteoroid: is a small rock or particle of debris in our solar system. They
range in size from dust to around 10 meters in diameter (larger objects are
usually referred to as asteroids).
Meteor: A meteoroid that burns up as it passes through the Earth’s
atmosphere is known as a meteor. If you’ve ever looked up at the sky at
night and seen a streak of light or ‘shooting star’ what you are actually
seeing is a meteor.
Meteorite: A meteoroid that survives falling through the Earth’s
atmosphere and colliding with the Earth’s surface is known as a meteorite.