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Finding dwarf planets
What is a planet?
A planet is a body orbiting around the sun with enough mass and therefore gravity to be
round. A planet has also ‘cleared its neighbourhood’, orbit by sucking in small bodies or
deflecting them away from their orbit. There are eight planets within our Galaxy:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
What is a dwarf planet?
The International Astronomical Union (IAU) adopted the term dwarf planet in 2006 for
objects in the solar system that were not quite planets but bigger than the other objects
in the solar system such as comets and asteroids. Dwarf planets also orbit the sun and
are round but they have not cleared their neighbourhood and often orbit with other
similar sized bodies because their gravity is not great enough. Dwarf planets can often
be called the ‘in-between sized’ planets.
The official dwarf planets are: Pluto, Ceres, Eris, Makemake and Haumea
What is the Asteroid Belt?
The asteroid belt is the region of the Solar System located between the orbits of the
planets Mars and Jupiter. It is occupied by many irregularly shaped bodies called
asteroids, primarily composed of rock and metal. These asteroids orbit the sun, the time
in which it takes for an object to orbit the sun in the asteroid bet varies from about three
to six years. The asteroid belt is home to the dwarf planet of Ceres, this is the belt’s only
dwarf planet and the largest object in its orbit.
What is the Kuiper Belt?
The Kuiper Belt is a region of the Solar System beyond the planets extending from the
orbit of Neptune. It is similar to the asteroid belt, but is far larger, being 20 times as
wide and 20–200 times as massive. The Kuiper belt consists mainly of small rock, icy
bodies and is home to three dwarf planets, Pluto, Haumea and Makemake.
DWARF PLANETS
PLUTO:
Pluto is the best known dwarf planet because of its demotion from a planet to a dwarf
planet in 2006, Pluto is the second biggest dwarf planet (Eris is the biggest) and is
considered one of the largest member of a distinct population known as the Kuiper belt
objects (KBOs). Pluto was found in 1930 when Clyde Tombaugh was using a blink
comparator to compare photographic plates taken over a series of days. He discovered
that there one tiny object was moving relative to the background stars.
Pluto has three moons; its main moon is Charon was discovered in 1930. The smaller
less significant moons, Nix and Hydra, were discovered in 2005 and sice then 3 more
tiny moons have been found.
WHY IS PLUTO NOT A PLANET?
In 2006 the IAU decided on a new class, dwarf planets, for objects such as Pluto. This
meant that any new KBOs discovered of a similar size would also become dwarf planets,
without needing to consider whether they were planets or not.
DISCOVERING DWARF PLANETS
Dwarf Planets have been discovered in a number of ways. Unlike most planets which can
be easily found through looking through a telescope, dwarf planets are much harder to
find. This is because of their positions in the solar system. Most of the dwarf planets can
be located in the Kuiper Belt and are also incredibly small in comparison to other
Planets.
Dwarf planets used to be found by taking pictures of the same section of sky at different
time intervals (eg. every few days or hours). The billions of stars and galaxies always
appear stationary in sky, which means that anything that moves could be either a
satellite, dwarf planet, asteroid or comet. The objects that are found to be moving would
then be looked at and analysed until they are identified. For any astronomer this is a lot
of time and work, therefore most of the work is done by computer. Once the images are
taken using a robotically controlled telescope 10 computers at the observatory search
the images. Each day the computers locate different moving objects that then need to be
looked at by astronomers. Sometimes the images just show flaws in the photo but they
are often successful in finding new dwarf planets.
The moving object which is recognised by the telescopes only appears as a dot of light,
therefore it is necessary to research further in order to find out exactly what it is and
what size. The size of an object can be determined by heat radiating from the object,
and this can be done using a high-tech telescope, the Hubble Space Telescope. Though
this gives us a result it is not always reliable, as it has to look through objects in our
atmosphere.
WHAT MAKES DWARF PLANETS SO HARD TO FIND?
The most prominent factor in the difficulty of discovering Dwarf Planets is their size. As
they are much smaller than normal planets, and usually in the Kuiper belt (surrounded
by thousands of other objects) they are harder to detect. It takes a lot of time, money
and patience to discover. Another factor which makes these planets hard to discover is
their distance away from earth, they are a very far way away and incredibly small, which
does not make the process any easier.