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With Explore the Planets, investigate the planets, their moons, and understand the processes that shape them. By G. Jeffrey Taylor, Ph.D. See our DVD collection.

Our Solar System

Our solar system is filled with a wide assortment of celestial bodies - the Sun itself, our eight planets, dwarf planets, and asteroids - and on Earth, life itself! The inner solar system is occasionally visited by comets that loop in from the outer reaches of the solar system on highly elliptical orbits. In the outer reaches of the solar system, we find the Kuiper Belt and the Oort cloud. Still farther out, we eventually reach the limits of the heliosphere, where the outer reaches of the solar system interact with interstellar space. Solar system formation began billions of years ago, when gases and dust began to come together to form the Sun, planets, and other bodies of the solar system.

A near-Earth <a href="/our_solar_system/asteroids.html&dev=1">asteroid</a> - named 2012 DA14 by astronomers  passed within 17,200 miles from Earth on February 15, 2013. On closest approach at about 1:25 p.m. CST on February 15, although it was within the orbit of the <a href="/earth/moons_and_rings.html&dev=1">Moon</a> and even geosynchronous <a href="/space_missions/satellites.html&dev=1">satellites</a>, it didn't strike Earth!  Find out more from <a href="http://www.nasa.gov/mission_pages/asteroids/news/asteroid20130201315144.html">NASA</a>! Fragments of a meteorite hit Chelyabinsk, Russia on 2/15/2013 <a href="http://www.reuters.com/article/2013/02/15/us-russia-meteorite-idUSBRE91E05Z20130215">injuring over 500</a>. Learn about <a href="http://www.windows2universe.org/our_solar_system/meteors/meteors.html">meteors and meteorites</a>.<p><small><em>NASA/JPL-CalTech</em></small></p>Neptune's <a href="/neptune/lower_atmosphere.html&dev=1">atmosphere</a> shows
a striped pattern of
<a href="/neptune/atmosphere/N_clouds_overview.html&dev=1">clouds</a>.
This cloud pattern is very similar to that of
<a href="/jupiter/jupiter.html&dev=1">Jupiter</a> and
<a href="/saturn/saturn.html&dev=1">Saturn</a>.
Neptune even has a <a href="/neptune/atmosphere/N_clouds_GDS.html&dev=1">Great Dark
Spot</a> similar
to Jupiter's <a href="/jupiter/atmosphere/J_clouds_GRS.html&dev=1">Great
Red Spot</a>.
The Great Dark Spot of Neptune is thought to be a hole, similar to the hole
in the <a href="/earth/Atmosphere/ozone_layer.html&dev=1">ozone layer on
Earth</a>,
in the <a href="/physical_science/chemistry/methane.html&dev=1">methane</a> cloud
deck of Neptune.<p><small><em>Image courtesy of NASA</em></small></p><a href="/asteroids/asteroid_lutetia.html&dev=1">Lutetia</a> is a medium-sized <a href="/our_solar_system/asteroids.html&dev=1">asteroid</a>. It orbits the <a href="/sun/sun.html&dev=1">Sun</a> in the main asteroid belt between the planets <a href="/mars/mars.html&dev=1">Mars</a> and <a href="/jupiter/jupiter.html&dev=1">Jupiter</a>.  This lumpy object is about 96 km (60 miles) in diameter. It isn't a perfect sphere, though. Lutetia is 132 km (82 miles) across one way, but only about 76 km (47 miles) long in another direction. The European space probe <a href="/space_missions/robotic/rosetta_flyby_asteroid_lutetia_july_2010.html&dev=1">Rosetta flew past Lutetia</a> in July 2010, and gave us our first good look at the asteroid.<p><small><em>Image courtesy of ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA.</em></small></p>This historic image is the first ever taken from a spacecraft in orbit about <a href="/mercury/mercury.html&dev=1">Mercury</a>, the innermost planet of the solar system.  Taken on 3/29/2011 by <a href="/space_missions/robotic/messenger/messenger.html&dev=1">MESSENGER</a>, it shows numerous craters across the <a href="/mercury/Interior_Surface/Surface/surface_overview.html&dev=1">surface</a> of the planet.  Temperatures there can reach over 800F because Mercury is so close to the Sun and rotates so slowly.  MESSENGER entered orbit around Mercury earlier in March 2011.<p><small><em>NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington</em></small></p>Comets are <a href="/comets/comet_nucleus.html&dev=1">lumps</a> of ice
and dust that periodically come into the center of the solar system from
its <a href="/comets/Oort_cloud.html&dev=1">outer
reaches</a>.
Some comets make <a href="/comets/perihelion_pass.html&dev=1">repeated
trips</a> to the inner
solar system. When comets get close enough to the Sun, heat
makes them start to <a href="/comets/sublimation.html&dev=1">evaporate</a>.
Jets of gas and dust form long
<a href="/comets/tail.html&dev=1">tails</a> that we can see from
Earth. 
This photograph shows <a href="/comets/comets_table.html&dev=1">Comet
Kohoutek</a>,
which visited the inner solar system in 1973.  It has an
<a href="/physical_science/physics/mechanics/orbit/orbit_shape_interactive.html&dev=1">orbit</a> of
about 75,000 years!<p><small><em>Image courtesy of NASA</em></small></p>New observations by the MESSENGER spacecraft provide  support for the hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed (shown in red) polar craters. Areas where polar deposits of ice imaged by Earth-based radar are shown in yellow.<p><small><em>Image courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory</em></small></p>

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF