Pluto, the runt of the solar system, is still a mystery
to astronomers in many ways. But thanks to a new study of the dwarf planet's
atmosphere, this misunderstood place is a little more known to us now.
Using the European Southern Observatory's (ESO) Very
Large Telescope in Chile, researchers made the first ever quantitative
measurement of the chemical composition of the atmosphere around Pluto. The
study revealed that the dwarf
planet's air is warmer, and contains more methane, than previously thought.
The astronomers discovered that Pluto's atmosphere is
warmer than its surface — though not by much. The air is a
frigid -292 degrees Fahrenheit (-180 degrees Celsius), while the dwarf planet's
face is -364 degrees Fahrenheit (-220 degrees Celsius). The researchers think
some patches of pure methane in the atmosphere, or perhaps a methane-rich layer
covering the surface, create this warming effect.
"Pluto is pretty far out there, so to me it was amazing
that we got this data at all," ESO researcher Hans-Ulrich Käufl told SPACE.com.
"It was well known that Pluto had an atmosphere, but it's really the very first
quantitative measurement of it. We were surprised that it is that
warm."
Pluto's atmosphere is very different from Earth's: It is
a tenuous layer of nitrogen, methane, and carbon monoxide that
is only present for part of Pluto's 248-year-long, elongated orbit. When the tiny
world gets very far away from the sun, the gaseous atmosphere freezes and falls
to the ground. The pressure of Pluto's atmosphere is only about one
hundred-thousandth of that on Earth.
"It might look like a vacuum, like on the moon," Käufl
said. "At this point we cannot really say if there is haze, but you might see
some kind of cirrus clouds. They would be white and gray."
Because of the atmosphere's thin substance, and Pluto's
small size and extreme
distance, gathering data about the atmosphere before now has been
difficult. Previous studies noticed the unique
seasonal changes in Pluto's atmosphere as the dwarf planet moves closer and
farther away from the Sun.
The team harnessed the Very Large Telescope (VLT)'s
strong observing power, adaptive optics technology to reduce blurriness caused
by turbulence in Earth's atmosphere, and a high-resolution instrument called a
spectrograph to make their measurements.
The CRyogenic InfraRed Echelle Spectrograph
(CRIRES) on the VLT separated light from Pluto's atmosphere into its
constituent colors, enabling the researchers to tell what elements in the air
the light passed through. The new data, which was significantly more detailed
than any previous measurements, allowed the researchers to compare their
findings to sophisticated computer simulations to understand how different
chemicals in the atmosphere affect temperatures.
"The combination of CRIRES and the VLT is almost
like having an advanced atmospheric research satellite orbiting Pluto," Käufl said.
Kaufl, with a team led by Emmanuel Lellouch of France's
Observatoire de Paris, reported the findings in a paper to be published in the
journal Astronomy & Astrophysics.
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