This week’s guess the planet image comes from Pluto and
shows the jagged peaks of the al-Idrisi mountains. These massive blocks of
water ice are jumbled together along the edges of sputnik planitia, part of the
bright heart shaped region of Pluto which was revealed by the new Horizons
spacecraft. Credit for this image naturally goes to the New Horizons team, who
have a full description of the image here.
They note in their description that both the al-Idrisi
mountains and the “sputnik planum” are “informally named”. This means that
these were the names which the New Horizons team assigned to them when their
spacecraft first got to Pluto. We had never had a detailed view of this remote
world before, so almost all its surface features needed to be assigned names in
order for the scientists working on the project to start to describe them. In this
situation informal names are assigned and must later be approved by the International
Astronomical Union. The IAU ensure that the names for planetary features fit
into a clear and coherent naming scheme.
Most planetary names have two components. The first part of
the name is specific to the feature and is chosen according to a naming theme.
In the case of this area of Pluto Sputnik Planitia was named after the first
human spacecraft, while the al-Idrisi mountains are named for the medieval explorer.
Themes are used to keep these names consistent. In the case of Pluto all mountain
ranges are named after explorers, with other ranges being named for Tenzing
Norgay and Edmund Hillary, the first people to climb mount Everest. Other
features on the dwarf planet are named after creatures of the underworld, gods
and monsters drawn from the folklore of numerous cultures, as well as more
modern literature.
The second part of the name is a description of the type of
feature it is. Many of these descriptive terms are in Latin, for example “planitia”
denotes a plain, “mons” a mountain and so on. This is a relic of the early days
of planetary nomenclature when much of international science was conducted in Latin,
and astronomers used that language to name the features they saw through their
telescopes. Wikipedia has quite a good list of translations for the commonly
recognised latin terms, which can be useful for decoding what a feature is from
its name.
More information about planetary names can be found in the
IAU’s Gazetteer of Planetary Nomenclature which lists all of the approved names
for features on various planets and moons.
It’s interesting to note that the name of the Sputnik plains
has changed as part of the process of studying pluto. The caption to the image
I shared earlier in the week describes it as “Sputnik Planum”, which was the
original name that was proposed when images from New Horizons first identified
the area. Planum indicates a plateau, whereas the area is now generally
considered to be a plain, and so is named “Planitia”. This demonstrates how our
understanding of features can change the names we apply to them.
The somewhat eclectic mix of Latin and cultural references
can make the sphere of planetary science seem confusing at times. However it
has some major advantages as it means that features are classified in a much
more consistent manner than they are on Earth. On our home planet we have been
coming up with place names for millennia, naming things in thousands of
different languages and dialects. This means that many cultures have their own
names for the same types of features. Places have often been named multiple
times, by different cultures to explore them, such as mount Everest, which was
named as such by the British, despite it already having names in both Nepalese (Sagarmāthā) and Tibetan
(Chomolungma). The debate as to which of these should be considered the
official name for the mountain is culturally and politically charged. When
exploring new worlds we have the ability to name things in a fresh and,
largely, consistent manner.
Further reading:
Informal names for features on Pluto.
Image Credit:
NASA/JHUAPL/SwRI
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