Transcript Solar System - Cloudfront.net

Solar System
• Our solar system consists of
– Sun
– 9 planets
– Asteroid Belt
– Meteors and comets
– Interplanetary medium
How was it formed?
• http://imgsrc.hubblesite.org/hu/db/2003/19/
images/f/formats/pdf.pdf
• Two Planet Forming Scenarios
• The Solar System formed when a cold, slowlyrotating cloud of gas and dust collapsed
because of its own gravity about 4.5 billion years
ago.
• As the Sun grew hot enough to ignite the nuclear
reactions which sustain it today, it vaporized the
cold ices and frozen gasses in the inner solar
system, leaving behind the rocky dust and
metals which form the inner planets.
• The outer Solar System remained cold, and the
ices and gas there collected into the giant outer
planets
Two General Categories
• Terrestrial planets (like the Earth)
– The terrestrial planets- Mercury, Venus, Earth and
Mars- are relatively small and have rocky crusts and
small atmospheres.
• Jovian planets (like Jupiter).
– The Jovian planets- Jupiter, Saturn, Uranus and
Neptune- are many times larger and have dense,
gaseous atmospheres with no visible surfaces.
– Sometimes referred to as gas giants, although it is
believed that the cores of these huge planets are
liquid if not solid forms of helium and hydrogen
• Pluto, the most distant planet, is in a class by
itself
MERCURY
• Timocharis made the first recorded observation of
Mercury in 265 BC.
• Other early astronomers that studied Mercury include
Zupus (1639), who studied the planet's orbit.
• Because it is so difficult to make out features on the
surface of the planet from Earth, it was not until the
1960s that scientists determined the correct day length
rate (59 Earth days) of the planet on its axis. This also
showed that Mercury's day length and year length are
the same.
• 1974 Mariner 10 passed by the planet 3 times and gave
us close-up images
• 2004 Messenger mission
Mercury
VENUS
• Venus is the second planet from the Sun, and is
Earth's neighbor in the solar system.
• Venus is the brightest object in the sky after the
Sun and the Moon, and sometimes looks like a
bright star in the morning or evening sky.
• We can't see the surface of the planet because it
has a very thick atmosphere filled with clouds
that strongly reflect sunlight. Observations of
Venus in the ultraviolet show cloud features that
relate to characteristics of the planet's
atmosphere.
• We think that the internal structure of Venus is
similar to Earth, with a metallic core, rocky
mantle, and crust.
• The atmosphere of Venus produces hostile conditions at
the planet's surface, where temperatures can reach
more than 460C (900F), atmospheric pressure is 90
times that at the Earth's surface, and clouds filled with
sulfuric acid surround the planet.
• spacecraft mapped the surface of the planet from above.
These maps reveal a surface covered with craters, over
1600 major volcanoes, mountains, large highland
terrains, and vast lava plains.
• The 1950's astronomer Robert Richardson noticed that
Venus rotates opposite from earth
MARS
• Mars Student Imaging Project
– Lets students pick a spot for the orbiting
Odyssey Spacecraft to take a picture
– http://msip.asu.edu/index.html
• http://marsrovers.jpl.nasa.gov/mission/trav
erse_maps.html
– Latest information on the two Mars rovers,
Spirit and Opportunity
• The uniquely red surface of Mars is marked by many
interesting features - some like those on the Earth and
others strangely different. The reddish color is caused by
rust (iron oxide) in the soil.
– Some of these features are; volcanoes, canyon systems, river
beds, cratered terrain, and dune fields.
• Of these features, the most interesting includes the
apparently dead volcano Olympus Mons, which rises 23
km (~75,000 ft) above the surrounding plains and is the
highest known peak in the Solar System.
• Valles Marines is a giant canyon system that runs about
2,500 miles across the surface of the planet and reaches
depths of 6 km or 4 miles
– (for comparison, the Grand Canyon is not more than 1 mile
deep).
ASTEROID BELT
• Asteroids are small bodies that are thought to be left
over from the beginning of the solar system 4.6 billion
years ago. They are rocky objects with round or irregular
shapes up to several hundred km across, but most are
much smaller.
• More than 100,000 asteroids lie in a belt between Mars
and Jupiter. These asteroids lie in a location in the solar
system where there seems to be a jump in the spacing
between the planets. Scientists think that this debris may
be the remains of an early planet, which broke up early
in the solar system. Several thousand of the largest
asteroids in this belt have been given names.
• The chances of an asteroid colliding with Earth are very
small! But some do come close to Earth, like Hermes
(closest approach of 777,000 km).
Formation of the Asteroid Belt
• One theory suggests that they are the
remains of a planet that was destroyed in
a massive collision long ago.
• More likely, asteroids are material that
never coalesced into a planet.
– In fact, if the estimated total mass of all the
asteroids was gathered into a single object,
the object would be less than 1,500
kilometers (932 miles) across - less than half
the diameter of the Moon.
JUPITER
• The Giant planets do not have the same layered
structure that the terrestrial planets do. Their evolution
was quite different than that of the terrestrial planets, and
they have less solid material.
• Jupiter's interior composition is primarily that of simple
molecules such as hydrogen and helium, which are
liquids under the high pressure environments found in
the interiors of the outer planets, and not solids.
• Motions in the interior of Jupiter contribute in a very
special way to the development of the powerful and
extensive magnetosphere of Jupiter. Heat generated
within
• Jupiter contributes to the unusual motions of the
atmosphere.
Giant Red Spot
• A giant, hurricane-like storm system that
rotates with the clouds of Jupiter.
• It is so large three complete Earths could
fit inside it.
• Astronomers have recorded this giant
storm on Jupiter for over 300 years.
Rings
• Rings are much smaller and fainter than
the famous rings of Saturn
• Their composition is small-grained, rocky
material; no ice. Contributes to their small
albedo (reflectiveness)
• Voyager 1 mission scientists decided to
look around and were surprised to find
them
Shoemaker-Levy9 Impact
• On 1994 July 16-22,
over twenty fragments
of comet ShoemakerLevy 9 collided with
the planet Jupiter
SATURN
• Saturn is the most distant of the five planets known to
ancient stargazers.
• In 1610, Italian Galileo Galilei was the first astronomer to
gaze at Saturn through a telescope. To his surprise, he
saw a pair of objects on either side of the planet, which
he later drew as "cup handles" attached to the planet on
each side.
• In 1659, Dutch astronomer Christiaan Huygens
announced that this was a ring encircling the planet.
• In 1675, Italian-born astronomer Jean Dominique
Cassini discovered a gap between what are now called
the A and B rings.
• Saturn is a gas giant. It is made mostly of
hydrogen and helium.
• volume is 755 times greater than Earth's.
• Winds in the upper atmosphere reach 500
meters per second in the equatorial region. (In
contrast, the strongest hurricane-force winds on
Earth top out at about 110 meters per second.)
• These super-fast winds, combined with heat
rising from within the planet's interior, cause the
yellow and gold bands visible in its atmosphere
URANUS
• Uranus is the seventh planet from the Sun and is
the third largest in the solar system.
– It was discovered by William Herschel in 1781.
• It has an equatorial diameter of 51,800
kilometers (32,190 miles) and orbits the Sun
once every 84.01 Earth years.
• It rotates about its axis once every 17 hours 14
minutes. Uranus has at least 22 moons.
• Uranus is distinguished by the fact that it is
tipped on its side.
– Its unusual position is thought to be the result
of a collision with a planet-sized body early in
the solar system's history
• In 1977, the first nine rings of Uranus were
discovered. During the Voyager
encounters, these rings were
photographed and measured, as were two
other new rings and ringlets.
NEPTUNE
• Neptune is the outermost planet of the gas
giants.
• It has an equatorial diameter of 49,500
kilometers (30,760 miles).
– If Neptune were hollow, it could contain nearly
60 Earths.
• Neptune orbits the Sun every 165 years.
• Neptune is a dynamic planet with several
large, dark spots reminiscent of Jupiter’s
hurricane-like storms.
• The largest spot, known as the Great Dark
Spot is about the size of the earth and is
similar to the Great Red Spot on Jupiter.
• Voyager revealed a small, irregularly
shaped, eastward-moving cloud scooting
around Neptune every 16 hours or so.
– This scooter as it has been dubbed could be a
plume rising above a deeper cloud deck.
PLUTO
• Tiny (only slightly larger than our Moon)
• Orbit is inclined more than 17 degrees
compared to the orbits of the other
planets, and its
• Orbit is also very eccentric (its distance
from the Sun varies over the course of its
orbit).
– It's so eccentric, in fact, that it even crosses
Neptune's orbit, so sometimes Neptune is
farther from the Sun than Pluto
• Recently the Hubble Telescope has taken
pictures of two moon circling Pluto and
Charon.
• In 2004 the international science
community had re-defined Pluto as a
dwarf planet.
• Since that time dozens of small Planetoids
have be discovered in our Solar system.
• Ceres, Eris, Sedna, Biden, VP113,
Comparing Rotation
Visualizing the Distance Between
Planets
• http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es2701/es
2701page01.cfm?chapter_no=visualizatio
n
– This animation is 300 times the speed of light.
Beyond the planets
• Oort Cloud
– An immense spherical cloud surrounding the
planetary system and extending approximately
3 light years, about 30 trillion kilometers from
the sun.
– This vast distance is considered the edge of the
Sun's orb of physical, gravitational, or
dynamical influence
– Source of long-period comets
• Kuiper Belt
– Starting in 1992, astronomers have become
aware of a vast population of small bodies
orbiting the sun beyond Neptune.
– There are at least 70,000 "trans-Neptunians"
with diameters larger than 100 km in the
radial zone extending outwards from the orbit
of Neptune (at 30 AU) to 50 AU
– Source of short-period comets
– Oort Cloud
COMETS
• Comets are sometimes called dirty
snowballs or "icy mudballs".
– They are a mixture of ices (both water and
frozen gases) and dust that for some reason
didn't get incorporated into planets when the
solar system was formed.
• This makes them very interesting as
samples of the early history of the solar
system.
Parts of a comet
• nucleus: relatively solid and stable, mostly ice and gas
with a small amount of dust and other solids;
• coma: dense cloud of water, carbon dioxide and other
neutral gases sublimed from the nucleus;
• hydrogen cloud: huge (millions of km in diameter) but
very sparse envelope of neutral hydrogen;
• dust tail: up to 10 million km long composed of smokesized dust particles driven off the nucleus by escaping
gases; this is the most prominent part of a comet to the
unaided eye;
• ion tail: as much as several hundred million km long
composed of plasma and laced with rays and streamers
caused by interactions with the solar wind
Nucleus of Halley’s Comet
METEORS
• A meteor is a bright streak of light in the
sky (a "shooting star" or a "falling star")
produced by the entry of a small meteoroid
into the Earth's atmosphere.
• When they hit the Earth’s surface they are
called Meteorites
Meteorites
• 3 Types
– Chrondrite (Stony)
• Most Common
– Carbonaceous Chrondrite
• Contain Organic Compounds
– Iron
• Composed mostly of Iron and Nickel
• The largest found meteorite (Hoba, in
Namibia) weighs 60 tons.
Chondrite (Stony) Meteorite
Iron Meteorite
Carbonaceous Chondrite
Hitting Earth
When is a heavenly body a planet?
a star? a piece of space debris?
• If there were a textbook definition of planet, it
would likely describe an object that forms out of
the swirling disk of dust and gas left after the
formation of a star.
– That also orbits a star
– That does not generate enough heat to burn
deuterium
A planet is a spherical object never capable of core
fusion, which is formed in orbit around an object in
which core fusion occurs at some time
Small Planet?
• Many astronomers think that Pluto should
never have been called a planet.
– It is only 1,430 miles (2,300 kilometers) wide,
smaller than Earth's Moon.
– It travels an elongated orbit that also dips
above and below the plane of Earth's orbit by
17.1 degrees.
– There are Kuiper Belt Objects (KBOs) that
approach the size of Pluto
• A newly proposed definition for planets that
would instantly boost the solar system's
tally to 12
– one large, round asteroid, and
– at least two faraway and icy brethren of Pluto.
• The middle road in the argument, which is
winning so far, goes like this:
– Pluto is a planet, and the public would be
confused and even upset to change that.
– Leave it as the ninth and final planet,
• but scientifically keep in mind that it's a KBO and
don't otherwise increase the count of planets in our
solar system
Brown Dwarfs
• Brown dwarfs are the ill-defined middle ground
between planets and stars.
• A star is a star because it shines on its own,
generating light through thermonuclear reactions
in which hydrogen is converted to helium.
• Brown dwarfs, though they can burn deuterium
in another type of reaction called "core fusion,"
fall short of full-blown stellar thermonuclear
fusion.
ON-LINE ACTIVITIES
• On-line Solar System Quiz
•
http://www.the-solarsystem.net/index.html
• Virtual Solar System
•
http://www.nationalgeographic.com/sol
arsystem/index.html