2Planets3 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 sunHas to be large enough that its own gravity pulls it into a round shapeMust be dominant enough to clear the area around it
3More on planetsInferior planets – planets between Sun and Earth (show phases like the moon)Superior planets – planets further from the Sun than Earth; always appear full
5Inner Planets Which ones are the inner planets? Mercury, Venus, Earth, MarsInner planets are also called terrestrial planets. Why?
6Inner Planets Which ones are the inner planets? Mercury, Venus, Earth, MarsInner planets are also called terrestrial planets. Why?They are made mainly of rock and iron-nickel compoundsGenerally smaller in size
8Mercury 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 nightHard to collect data from Mercury
9Mercury 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
10VenusCalled Earth’s twin because the two planets are similar in size, mass, composition, and distance from the sunWhat makes them different?Venus has no ocean and thick clouds that spin rapidly and trap heat on the surfaceHas air pressure 90 times greater than Earth, making it hard to studyVenus’ day is longer than it’s year
11Earth 70% of Earth’s surface is covered in water Only planet in our solar system to harbor lifeAll of the things we need to survive are provided under a thin layer of atmosphere that separates us from the uninhabitable void of space
12Mars Small 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 mountain in the solar system, Olympus MonsCanyon system stretches a distance that equals New York to Los AngelesMars has seasons just like Earth
17Asteroid belt In between Mars and Jupiter Made up of thousands of rock fragments that orbit around the sunLargest asteroids have been reclassified; now called Dwarf planets
18Outer planetsWhich planets are included in the outer planets?
19Outer planets Which planets are included in the outer planets? Jupiter, Saturn, Uranus, Neptune
20Outer planets Which planets are included in the outer planets? Jupiter, Saturn, Uranus, NeptuneMade up mostly of frozen hydrogen and heliumAtmospheres can be made of thick layers of methane and ammonia
21Outer planets Also known as Gas Giants or Jovian Planets Known to have a lot of moons due to large mass and gravitational pullRecently, the Cassini spacecraft took pictures of auroras occurring on Saturn’s poles
22JupiterA gas planet – mostly made of frozen H and HeThe largest planet with more than twice the mass of all of other planets put togetherGreat Red Spot: an ongoing storm similar to a hurricane on EarthSo 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
23Saturn Another gas planet Smaller than Jupiter, but has a larger diameter because of it’s ringsHundreds of rings made of chunks of ice and rocks, each traveling in it’s own orbit around SaturnSaturn is the only planet with a density less than waterIts largest moon, Titan, shows us an atmosphere like Earth's before life developed.
32Kuiper BeltThis disk-shaped region of icy debris is about 4.5 to 7.5 billion km from the sunPluto is in the Kuiper BeltOver 1000 objects discovered in the belt
33Oort CloudThe Oort Cloud is an immense spherical cloud surrounding our Solar System.Said to be the outer edge of our solar systemScientists believe that this could be the area where comets come from that streak by the EarthSedna – farthest known object in our solar system, considered to be in the oort cloud¾ size of Pluto, freezing cold (-400 F) orbit takes 10,500 years
34Comets Mixtures of ices and dusts Least changed objects since the formation of the solar system5 parts: nucleus, coma, hydrogen cloud, dust tail and ion tailCan only see it when its near the sunHalley’s comet – visible from Earth every 76 years. Next time we will see it is 2062.
35Meteorites Called a meteoroid when it is in space When a meteoroid passes into Earth’s atmosphere, the light given off is called a meteorCalled a meteorite when the rock survives the atmosphere and impacts Earth’s surface
42Chicxulub crater – Yucatan Peninsula, Mexico More than 110 miles in diameterBelieved by scientists to be the meteor that lead to the extinction of the dinosaurs due to climate change it caused
43Vagabonds from Space Meteoroids 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.
44Near Earth ObjectsPotentially 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.
46Close CallFebruary 15, 2013Asteroid 2012 DA14so close that it passed inside the ring of geosynchronous weather and communications satellitesAt its closest, the asteroid will be only about 1/13th of the distance to the Moon
48ExoplanetsWhat does the word exo mean?What is an exoplanet?
49Exoplanets What does the word exo mean? What is an exoplanet? A planet outside of our solar system528 discovered by the end of 2011TODAY there are 909 confirmed with 2,704 possible othersAstronomers are trying to determine if any of these can harbor life