Download Finding Dwarf planets

Student 3: Low Merit
Finding Dwarf planets
With modern day technology more and more celestial bodies are being found in the
Kuiper Belt, a region that stretches from the orbit of Neptune at 30 AU to 50 AU from the
Sun. This has led to a reclassification of some celestial objects such as Pluto.
What is a dwarf planet?
In our Solar System, we have 8 planets. In order from the sun they are Mercury, Venus,
Earth, Mars (the rocky planets) and Jupiter, Saturn, Uranus and Neptune (the gas
giants). For something to be classified as a planet it must have the following
characteristics: It must also be big enough to be round due to the force of its own
gravity. It must orbit the sun. Finally, it must dominate and clear its neighbourhood
around its orbit. This means that it has a planet is the biggest in its orbit and has the
most gravity. It may have moons but no other large bodies will be in the same orbit.
“Dwarf planet” was a category made in 2006 due to the realisation that there may be
numerous objects like Pluto in our Solar System. Dwarf planets share the first two
characteristics but not the third.
Pluto is no longer classified as a planet but is now a dwarf planet in our Solar System.
Pluto that orbits the sun and is massive enough to be round because of the force of its
own gravity. But, the main reason that Pluto was demoted to a dwarf planet is because it
doesn’t dominate its neighbourhood around its orbit. Pluto’s ‘’moon’’ Charon is about half
of Pluto’s size compared to the other eight planets which are a lot bigger than their
moons. Pluto even happens to be a lot smaller than our moon. Also, Pluto has a very
untidy orbit, not clearing a path along it. Therefore, it is now deemed a dwarf planet.
Currently, there are 4 other known and classified dwarf planets not including Pluto. They
are Haumea, Makemake, Eris and Ceres. Haumea, Makemake and Eris are bits of ice and
rock that orbit out beyond Neptune. Ceres (which is also the Solar System’s largest
asteroid) lies in the main belt in between Mars and Jupiter. Eris has a single moon that is
called Dysnomia. Haumea has two moons that are called Hi’iaka and Namaka. Ceres and
Makemake do not have any moons.
Discovering dwarf planets
Ceres is the closest dwarf planet to the sun and earth because it lies in the Asteroid Belt
between Mars and Jupiter. Objects in the asteroid belt are easy to find so it is highly
unlikely that there are any other dwarf planets there. However, Pluto, Eris, Makemake
and Haumea lie in the Kuiper Belt beyond Neptune. Pluto is the most well-known dwarf
planet and Eris is the biggest. They are all said to be smaller than Earth’s moon (Pluto is
about a fifth of its mass and about a third of its volume). Eris, was one time referred to
as a 10th planet, sharing a lot of similarities to Pluto and it is even bigger than Pluto.
The Kuiper Belt was discovered in 1951 by a Dutch-American astronomer named Gerard
Kuiper. It is a disc of icy objects that orbit the sun beyond Neptune and extends 50 AU
from the Sun, and is part of the Solar System. Objects found in the Kuiper Belt are
referred to as KBOs (Kuiper Belt objects). The largest KBOs, Pluto being one of them,
are the ones that are called dwarf planets. It is estimated that there are over 70,000
KBOs in the Kuiper Belt. Many of these may be larger than Pluto.
The part of the Kuiper belt that is visible from the Earth's Northern Hemisphere has been
well observed but, until recently, a shortage of the appropriate instruments meant that
the area visible from the Southern Hemisphere hadn’t been very well explored. In 2011
14 KBOs were discovered in Pluto's neighbourhood, 3 of which may be new dwarf
planets. These were found in a small section of the Kuiper belt that was studied by
astronomers using a 1.3-meter Warsaw University Telescope in Chile. By estimation, the
biggest object is probably 620 kilometres wide. Pluto and Eris are both approximately
2,333 kilometres wide. Ceres, which is the smallest dwarf planet, is about 487
kilometres wide. Because of the fact that these new objects are not very big and are so
distant, the astronomers cannot say for sure at the moment whether they are actually
spherical and therefore able to be classified as dwarf planets.
The Kuiper belt is definitely filled with objects that are about the same size or the same
brightness of these three new bodies. There are actually 37 other objects that lie in the
Kuiper Belt that are at least as bright as the newfound possible dwarfs. The Southern
skies still need to be searched to get a wider view on filling our Solar System, though. It
is always possible that more objects will be found in the next region that is beyond the
Kuiper Belt. This is where Sedna is (another possible dwarf planet) which approximately
orbits at about 14.3 billion kilometres from the sun.
KBOs are difficult to find because they are so far away and because they have erratic
orbits, that is, they are very tilted relative to the plane the planets orbit on. This makes
looking for them quite hard. Also, the brightness, or “albedo” affects how easily they are
found. Brighter planets are more easily seen but it is still hard to tell exactly how far
away they are.
The Kuiper Belt part of the Solar System may have tens or even hundreds of dwarf
planets. Who knows how many will join Pluto and the other dwarf planets over the next
few years.