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Learn about planets outside our solar system through Exoplanets and Alien Solar Systems by Tahir Yaqoob, Ph.D., a book in our online store book 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&edu=elem&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&edu=elem&dev=1">Moon</a> and even geosynchronous <a href="/space_missions/satellites.html&edu=elem&dev=1">satellites</a>, it didn't strike Earth!  Find out more from <a href="">NASA</a>! Fragments of a meteorite hit Chelyabinsk, Russia on 2/15/2013 <a href="">injuring over 500</a>. Learn about <a href="">meteors and meteorites</a>.<p><small><em>NASA/JPL-CalTech</em></small></p>Neptune's <a href="/neptune/lower_atmosphere.html&edu=elem&dev=1">atmosphere</a> shows
a striped pattern of
<a href="/neptune/atmosphere/N_clouds_overview.html&edu=elem&dev=1">clouds</a>.
This cloud pattern is very similar to that of
<a href="/jupiter/jupiter.html&edu=elem&dev=1">Jupiter</a> and
<a href="/saturn/saturn.html&edu=elem&dev=1">Saturn</a>.
Neptune even has a <a href="/neptune/atmosphere/N_clouds_GDS.html&edu=elem&dev=1">Great Dark
Spot</a> similar
to Jupiter's <a href="/jupiter/atmosphere/J_clouds_GRS.html&edu=elem&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&edu=elem&dev=1">ozone layer on
in the <a href="/physical_science/chemistry/methane.html&edu=elem&dev=1">methane</a> cloud
deck of Neptune.<p><small><em>Image courtesy of NASA</em></small></p><a href="/asteroids/asteroid_lutetia.html&edu=elem&dev=1">Lutetia</a> is a medium-sized <a href="/our_solar_system/asteroids.html&edu=elem&dev=1">asteroid</a>. It orbits the <a href="/sun/sun.html&edu=elem&dev=1">Sun</a> in the main asteroid belt between the planets <a href="/mars/mars.html&edu=elem&dev=1">Mars</a> and <a href="/jupiter/jupiter.html&edu=elem&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&edu=elem&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>Have you ever seen the <a href="/earth/Magnetosphere/aurora.html&edu=elem&dev=1">Southern or Northern Lights</a>? Earth isn't the only planet that puts on these beautiful light shows, which are also called the "<a href="/earth/Magnetosphere/aurora.html&edu=elem&dev=1">aurora</a>". Aurora have been seen at both <a href="/saturn/saturn_polar_regions.html&edu=elem&dev=1">poles of Saturn</a>, too, as well as at the poles of <a href="/jupiter/magnetosphere/jupiter_aurora.html&edu=elem&dev=1">Jupiter</a>.  These "<a href="/earth/Magnetosphere/tour/tour_earth_magnetosphere_09.html&edu=elem&dev=1">curtains of light</a>" sometimes rise 1,200 miles (2,000 km) above the <a href="/saturn/atmosphere/S_clouds_overview.html&edu=elem&dev=1">cloud tops</a> near Saturn's poles. The <a href="/space_missions/HST.html&edu=elem&dev=1">Hubble Space Telescope</a> took this picture in 2004.<p><small><em>Image courtesy of NASA, ESA, J. Clarke (Boston University), and Z. Levay (STScI)</em></small></p>This historic image is the first ever taken from a spacecraft in orbit about <a href="/mercury/mercury.html&edu=elem&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&edu=elem&dev=1">MESSENGER</a>, it shows numerous craters across the <a href="/mercury/Interior_Surface/Surface/surface_overview.html&edu=elem&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&edu=elem&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&edu=elem&dev=1">outer
Some comets make <a href="/comets/perihelion_pass.html&edu=elem&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&edu=elem&dev=1">evaporate</a>.
Jets of gas and dust form long
<a href="/comets/tail.html&edu=elem&dev=1">tails</a> that we can see from
This photograph shows <a href="/comets/comets_table.html&edu=elem&dev=1">Comet
which visited the inner solar system in 1973.  It has an
<a href="/physical_science/physics/mechanics/orbit/orbit_shape_interactive.html&edu=elem&dev=1">orbit</a> of
about 75,000 years!<p><small><em>Image courtesy of NASA</em></small></p>

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA