Sedna is a big Trans-Neptunian Object. Here's what an artist thinks Sedna might look like.
Click on image for full size
Image courtesy NASA/JPL-Caltech/R. Hurt (SSC-Caltech)
Trans-Neptunian Objects (TNO)
The outer edge of our Solar System is not empty. There are many huge spheres of rock and ice out near Pluto's orbit and beyond. Astronomers have a name for everything further out than the planet Neptune. They call these icy worlds Trans-Neptunian Objects (TNOs).
The planet Pluto is a Trans-Neptunian Object. It is in a region called the Kuiper Belt. There are many other giant ice balls in the Kuiper Belt. The Kuiper Belt is just outside of Neptune's orbit. Quaoar is another large Kuiper Belt Object.
Some TNOs are much, much further out than the Kuiper Belt. They are part of the Oort Cloud. Sedna might be from the Oort Cloud.
Scientists think they have found at least one TNO bigger than Pluto. This "tenth planet" is officially called 2003 UB313, but it has the nickname "Xena". Xena might be a scattered disc object, another type of TNO. It may be kinda in between a KBO and something from the distant Oort Cloud.
Most comets come from the Oort Cloud and the Kuiper Belt.
You might also be interested in:
Pluto is a frigid ball of ice and rock that orbits far from the Sun on the frozen fringes of our Solar System. Considered a planet, though a rather odd one, from its discovery in 1930 until 2006, it was...more
Astronomers have discovered a new planetoid at the far edge of our Solar System. The new object, named Sedna, is probably almost as big as the smallest planet, Pluto. Sedna is very, very far away. It is...more
Do you know what a planet is? If so, you are doing better than professional astronomers! Right now astronomers aren't quite sure how to define a planet. Maybe you've heard that some astronomers think Pluto...more
Eris is a dwarf planet in our Solar System. Eris was one of the first three objects classified as a dwarf planet, along with Pluto and Ceres. Eris was first spotted in January 2005. Eris is a large sphere...more
Pluto has been officially demoted from its status as a planet. The International Astronomical Union (IAU), at a meeting in August 2006, voted on their first "official" definition of a planet....more
In 2006 the International Astronomical Union (IAU) approved a new classification scheme for planets and smaller objects in our Solar System. Their scheme includes three classes of objects: "small solar...more
Makemake is a dwarf planet in our Solar System. Makemake was discovered in March 2005 by a team of astronomers led by Mike Brown. Makemake officially became a dwarf planet in July 2008. There were three...more