Outer Solar System
The Trans-Neptunian objects (TNOs) are here. The region includes the Kuiper Belt, scattered disk and the Oort Cloud. The best known objects are Pluto and its moons, but there are comets too.
Dwarf Planet Tour for Kids
After all the fuss about Pluto, everybody knows that itīs a dwarf planet now. But itīs only one of five. Hereīs a mini tour of all five, including the one where a heatwave is the temperature of Antarctica, the one shaped like an egg, and one whose year is over 500 Earth years long. All aboard!
Dwarf Planets - a Tour
Join the dwarf planet tour. It will take you so far away that the Sun seems to be no more than another bright star. You'll see a dwarf planet the shape of an American football, one whose a month is the same length as its day, and the one that upset the fans of Pluto.
Eris - Dwarf Planet
In a tilted orbit in the scattered disk, it shook up the traditional Solar System. Was it bigger than Pluto, and therefore a planet? No, both of them ended up as dwarf planets. Eris named for the Greek goddess of discord was an apt name for an object whose discovery started so many arguments.
Eris and Pluto - They're not Twins
For nearly ninety years Pluto was our ninth planet. Then in 2006, much to the annoyance of some, it was no longer a planet, but a dwarf planet. What happened? Eris happened. Some call Eris and Pluto twin planets, but they aren't twins. Eris has a secret.
Pluto was once the last outpost of the Solar System. Now we realize that it's the gateway to the Kuiper Belt, a disk made up of rubble left over from the formation of the Solar System. The Kuiper Belt is big and it's cold and the Sun would just look like a bright star from there.
Kuiper Belt - Facts for Kids
Plutoīs not the last planet, itīs the first Kuiper Belt Object. The Kuiper Belt is made up of millions of icy bits left over from the beginning of the Solar System. It starts at 30 AU - thatīs 30 times farther from the Sun than the Earth. From there it stretches for another 2 billion miles!
Pluto - Gateway to the Kuiper Belt
NASA's New Horizons has been to visit Pluto, and we will be learning new things about it for years to come. Meanwhile here's a profile of dwarf planet 134340 Pluto, largest object in the Kuiper Belt and former planet. It has a lot of titles - and moons - for something so small.
Pluto Is a Dwarf Planet
Some people are still upset that Pluto isn't considered a planet any more. But was it ever really a planet?
The Oort Cloud - Facts for Kids
Where do comets come from? The Oort Cloud is home to a trillion comets at the edge of the Solar System, nearly half way to the next star. Sometimes they get kicked out and sometimes they come to visit the inner Solar System.
Top Astronomy Stories 2012
What were the big astronomy stories of the year 2012? Here is my choice of the top ten plus a non-story. What do you think?
Voyager 1 Gas Giants and a Last Look Homeward
When a rare planetary alignment opened up the outer Solar System, Voyager 1 was sent forth. It observed the gas giants Jupiter and Saturn and their moons. At nearly 4 billion miles from the Sun, the probe turned and took one last picture of home before continuing its journey to the stars.
Whatīs in a Name Astronomy Homepage | Editor's Picks Articles | Top Ten Articles | Astronomy Site Map
Things arenīt always what they seem. Many discoveries arenīt named for - or by - their discoverers. Halley didnīt discover Comet Halley. Kuiper said the Kuiper Belt didnīt exist. The Herschels called Uranus "the Georgian planet" after George III of England, but no one else did.
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