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.
Captured Moon - Triton Facts for Kids
Neptuneīs big moon Triton was nameless for over a hundred years after its discovery. And it was so far away that astronomers knew almost nothing about it. Then Voyager 2 visited and saw active ice volcanoes on a moon that is probably a cousin to Pluto.
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!
Easter Island and a distant dwarf planet what do they have in common? The answer is Makemake the creator god in the Rapa Nui mythology of Easter Island. How did his name come to be given to a small frozen body seven billion kilometers (four billion miles) from the Sun?
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.
Pluto Facts for Kids
A dwarf planet so far away that the Sun would look like a exceptionally bright star, so cold that its atmosphere is frozen for most of its year. This is Pluto, former planet, and now the gateway to the Kuiper Belt.
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?
Quaoar What Is It
Beyond Neptune lies the Kuiper Belt where tens of thousands of icy bodies are scattered over billions of miles of space. Quaoar, named for the Tongva creation god, is one of them. It seems to fit the criteria for a dwarf planet, but it's still not on the official list.
Rosetta the Comet Chaser
Rosetta, the European Space Agency (ESA) spacecraft, traveled for ten years and billions of miles in order to rendezvous with a comet, accompany it as it moved through the inner Solar System past the Sun, and deploy a lander.
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?
Top Five Dubious Astronomy Stories 2014
Have you read about the Top Ten Astronomy Stories for 2014? This article is complementary to it. Here are my choices for the top five debatable stories of the year. They were widely reported, but there isnīt really enough evidence to accept their conclusions.
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
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.
Why it took so long to discover Uranus Astronomy Homepage | Editor's Picks Articles | Top Ten Articles | Astronomy Site Map
The sky is full of stars, and since prehistoric times humans have known of five nomads planets wandering among them. No individual discovered those planets, for they're there for all to see. So why was the sixth one now called Uranus not known until 1781?
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