Transcript The Solar System

The Solar System
What is a planet?
Old Definition
a large, solid body that shines by reflecting
sunlight and revolves in a stable orbit
around the Sun
What is a planet?
New Definition
3 major criteria are required to classify an
object as a planet:
– a large solid body that shines by reflecting
sunlight and revolves in a stable orbit around
the sun (old definition)
– large enough that its own gravity pulls it into a
round shape
– dominant enough to clear the path of its orbit
(its in orbit by itself)
What does the word exo mean?
Exoplanets
• “Exo” means “outside.”
• What is an exoplanet?
Exoplanets
– a planet in another
solar system
– more than 2000 have
been discovered so
far
– New York Times
Science Section
February 3, 2015
announced the
discovery of an
exoplanet with rings
200 x larger than
Saturn’s rings
Sherlock Holmes and Dr. Watson are camping.
They pitch their tent under the stars and go to
sleep.
Sometime in the middle of the night, Holmes
wakes Watson and says, “Watson, look up at
the stars and tell me what you see.”
Watson says, “I see millions of stars and even
if a few of those have planets, it’s quite likely
there are some planets like Earth, and if there
are a few planets like Earth out there, there
might also be life.”
Holmes replies, “Watson, you idiot! Someone
stole our tent!”
Classifying Planets
• Inferior planets – planets between Sun and
Earth (show phases like the moon)
• Superior planets – planets farther from the Sun
than Earth; always appear full
Classifying Planets
Inner Planets are
between the Sun and
the Asteroid Belt. They
are inside the belt.
Outer Planets are
farther from the Sun.
They are outside the
Asteroid Belt.
The Asteroid Belt is
between Mars and
Jupiter.
What is missing?
Inner Planets
• The inner planets are:
– Mercury, Venus, Earth, Mars
• Inner planets are also called terrestrial
planets. Why?
Inner Planets
• The inner planets are:
– Mercury, Venus, Earth, Mars
• They are called terrestrial planets because
they are made mainly of rock and ironnickel compounds.
Mercury
Mercury has almost no gravity so it cannot hold on to an
atmosphere. Although there is a little gas around it, it’s not
enough to be considered an atmosphere. Without an atmosphere
and being close to the sun causes temperatures to be very high
during the day and very low at night.
Venus
retrograde rotation
Venus rotates clockwise
very slowly probably
because it was hit by a
very large object a long
time ago. Clockwise is
opposite most planets
so it’s called retrograde
rotation.
Called Earth’s twin
because they have
similar gravity, mass,
and are close to one
another.
Air pressure is 90 times
greater than Earth!
Because of its thick
atmosphere, a lot of
heat is trapped, making
the planet very hot.
Earth
Mars is red due to
the iron oxide in the
soil. The largest
volcano in the solar
system is on Mars.
Mars was names
after the god of war.
The names of its two
moons, Phobos and
Deimos, mean panic
and fear.
Currently there are
several satellites in
orbit around Mars
and several rovers
on its surface.
Crewed missions to
Mars are planned.
Mars
The Asteroid Belt separates the
Inner and the Outer Planets.
Asteroid belt
• consists of thousands
of rock fragments in
orbit around the Sun
• largest of them are
called minor planets
• the largest asteroid,
Ceres, has been
reclassified as a
dwarf planet
Many objects in the Asteroid Belt
have names.
Asteroid Belt
This is Ceres. Why is it a dwarf planet?
• Vesta is 330 miles
wide and made of
basalt
• Is a protoplanet –
an object left over
from the formation
of the solar system.
• It is the second
largest object in the
asteroid belt.
Vesta as seen by
the Dawn probe in
orbit 330 miles
away. The colors
were chosen to
highlight certain
areas: green for
iron, orange for
debris thrown out of
an impact crater.
Dawn reached Ceres in Dec. 2015
Kupalo Crater as seen from 240 miles above
Infrared mapping with a spectrometer will
determine what minerals are on the surface.
The Outer Planets are outside of
the Asteroid Belt.
↓
Outer Planets
• The outer planets are:
– Jupiter, Saturn, Uranus,
Neptune
• made mostly of frozen
hydrogen and helium
• atmospheres made of
thick layers of methane
and ammonia
• ALL have rings
Outer Planets
• also known as Gas
Giants or Jovian Planets
• have a lot of moons due
to their large mass and
gravitational pull
• moons are small and
have retrograde orbits
(revolve around planets in
clockwise direction)
Jupiter
largest planet in the solar
system with the strongest
magnetic field, which
creates auroras.
radiates more heat into
space than it receives from
the sun
has spots
Saturn
takes 30 years to
complete one orbit
around the sun
lowest density of
any planet; its
density is lower
than that of water!
radiates more
heat than it
receives
has a strong
magnetic field
Hubble captured photographs of the auroras
on Saturn! Saturn also has cyclones.
Saturn has a famous moon named
Enceladus
Enceladus - Saturns moon - YouTube
Uranus – rotates on its side probably
because something large crashed into it a
long time ago
even though the planet
is tipped over, its
magnetic field is not
has a blue color due to
the methane gas in its
atmosphere
so far from the sun that
its temperature is -200
degrees Celsius
has 42 years of dark
winter followed by 42
years of constant
summer
Centaurs
• objects between
Jupiter and
Neptune with
unstable orbits
• 9 have been
named so far
• may become
comets
Neptune
discovered
mathematically
magnetic axis is
tipped and is not at
the center of the
planet
has winds of 2000
kilometers per hour
Pluto 1935
Pluto was
discovered at the
Lowell Observatory
in Arizona by an
astronomer working
in this small
building. (Yes,
that’s me!)
In 2005, Mike Brown made
discovered a tenth planet,
Eris.
This discovery ignited a
firestorm of controversy.
The debate ended with the
demotion of Pluto from real
planet to “dwarf” planet.
Suddenly Brown was
receiving hate mail from
schoolchildren and being
bombarded by TV
reporters.
The book is very good!
Pluto is not a planet anymore!
Why?
• Pluto does not orbit
alone. There are
other objects in its
orbital path.
• Pluto’s orbit is not
stable. It crosses
Neptune’s orbit.
• Pluto is much
smaller and made of
rock, more like the
inner planets than
the outer planets.
The Kuiper Belt – Pluto is a Kuiper
Belt Object (KBO)
↓
The Kuiper Belt
• a region of debris 50 to 55 Astronomical
Units (AU) from the sun (4.5 to 7.5 billion km
or 2.8 to 4.6 billion miles)
• About 1500 objects in this belt have been
identified; there may be as many as 70,000
• the largest, like Pluto, are considered dwarf
planets
• next largest are called planetoids
• where short period comets come from
Pluto - Dwarf Planet
In 2006 Pluto was
reclassified as a
Dwarf Planet.
Dwarf Planets:
• are round
• orbit the sun
• are not moons
• cannot clear their
orbital path
2011 – A 4th moon discovered!
2012 – A 5th moon discovered!
Results of the Name the Moons
of Pluto contest in 2013
2 Pluto Moons Get New Names: Styx &
Kerberus | Space.com
Scroll down to second video.
Pluto's Moons |
Five Satellites of
Pluto |
Space.com
Use this
site if
you had
trouble
with the
link on
the page
before.
New Horizons Mission to Pluto
launched in 2006
The spacecraft carries a
new Florida quarter,
engraved with the
"Gateway to Discovery"
design, on the 3-billionmile journey.
The quarter serves a
purpose: scientists are
using it as a spinbalance weight on the
mission.
New Horizons
flew near
Pluto in 2015.
New
Horizons
Videos |
NASA
Pick any
video to
watch.
More Dwarf Planets
• CERES
– largest object in the asteroid belt (1/3 mass of asteroid belt)
– smallest dwarf planet
– only dwarf planet NOT in the Kuiper Belt
• ERIS (Greek/Roman goddess of strife and discord)
– Eris is larger than Pluto so logically either Eris had to be a
"planet" or Pluto had to be reclassified.
– largest dwarf planet, largest known member of the Kuiper Belt
– orbits 10,128,000,000 km from the Sun
• MAKEMAKE
• HAUMEA
January 2014
Dwarf Planet Ceres in the
Asteroid Belt has water jets!
Planet X
A new ninth planet has been
discovered! Like Neptune, Planet
X was found mathematically
when astronomers tried to
explain the orbits of extreme
Kuiper Belt objects.
Mike Brown (left) and Konstantin Batygin
California Institute of Technology
discovered Planet X, February 2016
• 10 times mass of Earth
• like a mini Neptune
• elliptical orbit 200 – 1200 AU
away from Sun
• beyond Kuiper Belt
• orbit takes 20,000 Earth years
• too far to see if we even knew
where to look for it!
Voyager 1
launched in 1977
finished a survey
of outer planets
in 1989
uses radioactive
power packs
travels at 17 km/s
its radio message
takes 16 hours to
reach Earth
Voyager has left the Heliosphere
The heliosphere is the immense magnetic
bubble containing our solar system, solar
wind, and the entire solar magnetic field. It
extends well beyond the orbit of Pluto.
Voyager 1 is now in
interstellar space.
Voyager 2 is in the
"Heliosheath" -- the
outermost layer of the
heliosphere where the
solar wind is slowed by
the pressure of interstellar
gas.
Voyager 1 – 134 AU from
Earth
Voyager 2 – 111 AU from
Earth; only spacecraft to
ever explore Uranus and
Neptune
Oort Cloud
• an immense spherical cloud surrounding our
Solar System at its outermost edge
• 5000 to 100,000 AU away
• may contain 2 trillion small objects
• where long period comets come from
• Sedna – farthest known object in our solar
system (8 billion miles away), considered to be
in the Oort Cloud
– ¾ size of Pluto; -400 F; orbit takes 10,500 years
– so far away that the Sun appears very small and
could be covered by the head of a straight pin
Comets
• Comets are small icy
bodies that release gas or
dust.
• They are the least changed
objects since the formation
of the solar system.
• 5 parts: nucleus, coma,
hydrogen cloud, dust tail
and ion tail
• tail always points away
from the Sun due to the
solar wind blowing it that
way
• can only be seen when
near the sun when heat
creates the coma and the
tails
Comets
go around the Sun
in long, oval orbits
– Short-period comets
need less than 200
years to complete
one orbit.
– Long-period comets
take 200 years or
longer to orbit the
Sun.
http://www.youtube.com/w
atch?v=C8zV1xiGqf4
On 1/15/06 a trip of
almost 3 billion miles
ended. A capsule
holding interstellar
and cometary
particles returned to
the Utah desert. In
1999, NASA sent
Stardust to Comet
Wild 2.
To capture tiny
particles in space,
NASA used the least
dense solid known,
aerogel. It is 99.8%
air, 1000 times less
dense than glass, and
provides 39 times
more insulation than
the best fiberglass
insulation.
Stardust