From Simple English Wikipedia, the free encyclopedia
Dwarf planet
is the name used to classify some objects in the
solar system
. This definition was made on August 24, 2006 by the
International Astronomical Union
(IAU), and can be described as;
a dwarf planet is a body orbiting the
Sun
that is big enough to round itself by its own gravity, but has not cleared its orbital path of other rival bodies
. At the same meeting the IAU also defined the term
planet
for the first time. Some astronomers think that the term "dwarf planet" is too confusing and needs to be changed.
The nine dwarf planets, in order from their distance from the
Sun
are:
- Ceres
(in the
Asteroid belt
)
- Orcus
- Pluto
. Pluto was named by an 11-year-old girl because it was the initials of the astronomer who found it.
[1]
- Haumea
- Quaoar
- Makemake
- Gonggong
- Eris
- Sedna
The dwarf planets, unlike the
terrestrial
and
gas giant planets
, are in more than one region of the
solar system
. Ceres is in the
asteroid belt
. The high
orbital eccentricity
of Pluto puts it mostly outside Neptune's orbit, but partly inside. The others are in the
trans-Neptune region
.
NASA
's
Dawn
and
New Horizons
missions reached Ceres and Pluto, respectively, in 2015.
Dawn
had already orbited and observed
Vesta
in 2011.
There are many other dwarf planets in the solar system. Most of them are also
Kuiper belt
objects.
- Ceres
was found by
Giuseppe Piazzi
on January 1, 1801. Classified as a dwarf planet on September 13, 2006.
- Pluto
was found by
Clyde W. Tombaugh
on February 18, 1930. Reclassified as a dwarf planet on August 24, 2006
- Haumea
was found by a team led by
Mike Brown
on December 28, 2004. Accepted as a dwarf planet on September 17, 2008.
- Makemake
was found by a team led by
Mike Brown
on March 31, 2005. Accepted as a dwarf planet on July 11, 2008.
- Eris
was found by
Mike Brown
and his science team on January 5, 2005. Accepted as a dwarf planet on September 13, 2006.
- ↑
Rincon, Paul 2006. The girl who named a planet.
[1]