The Solar System

Planets

• 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

– Has to be large enough that its own gravity pulls it into a round shape

– Must be dominant enough to clear the area around it

More on planets

• Inferior planets – planets between Sun and Earth (show phases like the moon)

• Superior planets – planets further from the Sun than Earth; always appear full

Inner Planets

• Which ones are the inner planets?

Inner Planets

• Which ones are the inner planets?– Mercury, Venus, Earth, Mars

• Inner planets are also called terrestrial planets. Why?

Inner Planets

• Which ones are the inner planets?– Mercury, Venus, Earth, Mars

• Inner planets are also called terrestrial planets. Why?– They are made mainly of rock and iron-nickel

compounds

Generally smaller in size

The Inner Planets

Also called terrestrial planets

Mercury

Closest to the sun

Made of the dense metals iron and nickel

Has almost no atmosphere, which makes it very hot during the day and very cold at night

Hard to collect data from Mercury

Mercury

• Considered an extreme planet– Smallest, most dense, the one with the oldest surface, the one

with the largest daily variations in surface temperature, and the least explored.

– Mercury also has a magnetic field around it like Earth

VenusCalled Earth’s twin because the two planets are similar in size, mass, composition, and distance from the sun

What makes them different?

Venus has no ocean and thick clouds that spin rapidly and trap heat on the surface

Has air pressure 90 times greater than Earth, making it hard to study

Venus’ day is longer than it’s year

Earth

70% of Earth’s surface is covered in water

Only planet in our solar system to harbor life

All of the things we need to survive are provided under a thin layer of atmosphere that separates us from the uninhabitable void of space

MarsSmall rocky body that was once thought to be very Earth-like

Mars’ atmosphere has 1% the pressure of Earth’s atmosphere and is made mostly of carbon dioxide. It appears red because the surface contains iron oxide, or rust.

Contains the largest volcanic Contains the largest volcanic mountain in the solar system, mountain in the solar system, Olympus Mons Olympus Mons

Canyon system stretches a Canyon system stretches a distance that equals New York distance that equals New York to Los Angelesto Los Angeles

Mars has seasons just like Earth

Evidence of seasons on Mars

Mars

• There are currently several probes and satellites around Mars and the Curiosity Rover on Mars

• There is a planned mission to Mars within the next 30 years.

Pictures sent from Curiosity

Asteroid belt

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Asteroid belt

• In between Mars and Jupiter

• Made up of thousands of rock fragments that orbit around the sun

• Largest asteroids have been reclassified; now called Dwarf planets

Outer planets

• Which planets are included in the outer planets?

Outer planets

• Which planets are included in the outer planets?– Jupiter, Saturn, Uranus, Neptune

Outer planets

• Which planets are included in the outer planets?– Jupiter, Saturn, Uranus,

Neptune

• Made up mostly of frozen hydrogen and helium

• Atmospheres can be made of thick layers of methane and ammonia

Outer planets

• Also known as Gas Giants or Jovian Planets

• Known to have a lot of moons due to large mass and gravitational pull– Recently, the Cassini

spacecraft took pictures of auroras occurring on Saturn’s poles

JupiterA gas planet – mostly made of frozen H and He

The largest planet with more than twice the mass of all of other planets put together

Great Red Spot: an ongoing storm similar to a hurricane on Earth

So big that it forms a miniature solar system (has 66 moons, some as big as planets)

Io, one of Jupiter’s moons, is covered with active volcanoes

SaturnAnother gas planet

Smaller than Jupiter, but has a larger diameter because of it’s rings

Hundreds of rings made of chunks of ice and rocks, each traveling in it’s own orbit around Saturn

Saturn is the only planet with a density less than water

Its largest moon, Titan, shows us an atmosphere like Earth's before life developed.

Image from Cassini

Hubble telescope picture of auroras occurring on Saturn

UranusGas Planet

Twice as far from the Sun as Saturn

Appears blue due to traces of methane gas in its atmosphere

Axis tilted at a 90° angle, rotating from top to bottom, cosmic collision?

Neptune

Discovered as a result of a mathematical prediction

Appears blue due to traces of methane gas in its atmosphere

So far away that it takes 165 years to orbit the sun

Centaurs

• Group of objects orbiting between Jupiter and Neptune

• 9 discovered so far

• Unstable orbits; astronomers believe that they are refugees from the Kuiper Belt

• Some may become comets

Dwarf Planets

• New classification occurred in 2006• Orbits around the sun, has enough mass and

gravity to pull it into a round shape, but does NOT clear the neighborhood around its orbit, NOT a moon

Dwarf Planets

• There are 5 dwarf planets known so far:

• Pluto• Ceres• Eris• Makemake• Haumea

Kuiper Belt↓

Kuiper Belt

• This disk-shaped region of icy debris is about 4.5 to 7.5 billion km from the sun

• Pluto is in the Kuiper Belt

• Over 1000 objects discovered in the belt

Oort Cloud

• The Oort Cloud is an immense spherical cloud surrounding our Solar System.

• Said to be the outer edge of our solar system• Scientists believe that this could be the area

where comets come from that streak by the Earth

• Sedna – farthest known object in our solar system, considered to be in the oort cloud– ¾ size of Pluto, freezing cold (-400 F) orbit takes

10,500 years

Comets

• Mixtures of ices and dusts

• Least changed objects since the formation of the solar system

• 5 parts: nucleus, coma, hydrogen cloud, dust tail and ion tail

• Can only see it when its near the sun

• Halley’s comet – visible from Earth every 76 years. Next time we will see it is 2062.

Meteorites

• Called a meteoroid when it is in space

• When a meteoroid passes into Earth’s atmosphere, the light given off is called a meteor

• Called a meteorite when the rock survives the atmosphere and impacts Earth’s surface

Meteor Crater, ArizonaIt’s circumference is 3 miles.

It is 550 feet deep (60 story building) and can hold 20 football fields on its floor.

Meteorite - Arizona

Mining operations occurred at the bottom. The area is now used by NASA for astronaut training because it resembles the surface of the moon.

Chicxulub crater – Yucatan Peninsula, Mexico

• More than 110 miles in diameter

• Believed by scientists to be the meteor that lead to the extinction of the dinosaurs due to climate change it caused

Vagabonds from SpaceMeteoroids

• Meteoroids are rocky or icy fragments that travel through space.

• NASA estimates that 1500 objects larger than 0.6 miles (1 km) across exist in orbits near Earth.

• The smallest of these could destroy a city. • The Near Earth Objects Program scans the

skies to detect, catalogue and monitor these asteroids.

• The goal was to identify 90% of them by 2008.

Near Earth Objects• Potentially Hazardous Asteroids (PHAs)

are space rocks larger than 100 meters in or near the asteroid belt that can come closer to Earth than 0.05 AU.

• None of the known PHAs is on a collision course with Earth.

• Astronomers continue to find new ones.

The Ones We Know About

Close Call

• February 15, 2013

• Asteroid 2012 DA14• so close that it passed

inside the ring of geosynchronous weather and communications satellites

• At its closest, the asteroid will be only about 1/13th of the distance to the Moon

Exoplanets

• What does the word exo mean?

Exoplanets

• What does the word exo mean?

• What is an exoplanet?

Exoplanets

• What does the word exo mean?

• What is an exoplanet?

– A planet outside of our solar system– 528 discovered by the end of 2011– TODAY there are 909 confirmed with 2,704 possible

others– Astronomers are trying to determine if any of these

can harbor life