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What Scientists Are Learning from the Eclipse

What Scientists Are Learning from the Eclipse

While millions of
people in North America headed outside to watch the eclipse on Aug. 21, 2017, hundreds of scientists got out telescopes, set up instruments, and
prepared balloon launches – all so they could study the Sun and its complicated
influence on Earth.


Total solar
eclipses happen about once every 18 months somewhere in the world, but the
August eclipse was rare because of its long path over land. The total eclipse
lasted more than 90 minutes over land, from when it first reached Oregon to
when it left the U.S. in South Carolina.


This meant that
scientists could collect more data from land than during most eclipses, giving
us new insight into our world and the star that powers it.

A moment in the Sun’s

During a total solar
eclipse, the Sun’s outer atmosphere, the corona, is visible from Earth. It’s
normally too dim to see next to the Sun’s bright face, but, during an eclipse, the
Moon blocks out the Sun, revealing the corona.


Image Credit: Peter Aniol, Miloslav Druckmüller and Shadia Habbal

Though we can
study parts of the corona with instruments that create artificial eclipses, some
of the innermost regions of the corona are only visible during total solar
eclipses. Solar scientists think this part of the corona may hold the secrets
to some of our most fundamental questions about the Sun: Like how the solar
wind – the constant flow of magnetized material that streams out from the Sun
and fills the solar system – is accelerated, and why the corona is so much
hotter than the Sun’s surface below.  

Depending on
where you were, someone watching the total solar eclipse on Aug. 21 might have
been able to see the Moon completely obscuring the Sun for up to two minutes
and 42 seconds. One scientist wanted to stretch that even further – so he used
a pair of our WB-57 jets to chase the path of the Moon’s shadow, giving their
telescopes an uninterrupted view of the solar corona for just over seven and half minutes.


telescopes were originally designed to help monitor space shuttle launches, and
the eclipse campaign was their first airborne astronomy project!


scientists weren’t the only ones who had the idea to stretch out their view of
the eclipse: The Citizen CATE project (short for Continental-America Telescopic
Eclipse) did something similar, but with the help of hundreds of citizen scientists. 

Citizen CATE included
68 identical small telescopes spread out across the path of totality, operated
by citizen and student scientists. As the Moon’s shadow left one telescope, it reached
the next one in the lineup, giving scientists a longer look at the way the
corona changes throughout the eclipse.


accounting for clouds, Citizen CATE telescopes were able to collect 82 minutes
of images, out of the 93 total minutes that the eclipse was over the US. Their
images will help scientists study the dynamics of the inner corona, including
fast solar wind flows near the Sun’s north and south poles.

The magnetized solar
wind can interact with Earth’s magnetic field, causing auroras, interfering
with satellites, and – in extreme cases – even straining our power systems, and
all these measurements will help us better understand how the Sun sends this
material speeding out into space.

Exploring the Sun-Earth

Scientists also
used the eclipse as a natural laboratory to explore the Sun’s complicated
influence on Earth.

High in Earth’s
upper atmosphere, above the ozone layer, the Sun’s intense radiation creates a
layer of electrified particles called the ionosphere. This region of the
atmosphere reacts to changes from both Earth below and space above. Such
changes in the lower atmosphere or space weather can manifest as disruptions in
the ionosphere that can interfere with communication and navigation signals.


One group of
scientists used the eclipse to test computer models of the ionosphere’s effects
on these communications signals. They predicted that radio signals would travel
farther during the eclipse because of a drop in the number of energized particles.
Their eclipse day data – collected by scientists spread out across the US and
by thousands of amateur radio operators – proved that prediction right.

In another
experiment, scientists used the Eclipse Ballooning Project to investigate the eclipse’s effects
lower in the atmosphere. The project incorporated weather balloon flights from
a dozen locations to form a picture of how Earth’s lower atmosphere – the part
we interact with and which directly affects our weather – reacted to the
eclipse. They found that the planetary boundary layer, the lowest part of
Earth’s atmosphere, actually moved closer to Earth during the eclipse, dropped
down nearly to its nighttime altitude.


A handful of these
balloons also flew cards containing harmless bacteria to explore the potential
for contamination
of other planets with Earth-born life. Earth’s stratosphere is similar to the surface of Mars, except in one main way:
the amount of sunlight. But during the eclipse, the level of sunlight dropped
to something closer to what you’d expect to see on Mars, making this the
perfect testbed to explore whether Earth microbes could hitch a ride to the Red
Planet and survive. Scientists are working through the data collected, hoping
to build up better information to help robotic and human explorers alike avoid
carrying bacterial hitchhikers to Mars.


Image: The small metal card used to transport bacteria.

Finally, our
EPIC instrument aboard NOAA’s DSCOVR satellite provided awe-inspiring views of the
eclipse, but it’s also helping scientists understand Earth’s energy balance. Earth’s energy system is in a constant
dance to maintain a balance between incoming radiation from the Sun and
outgoing radiation from Earth to space, which scientists call the Earth’s
energy budget. The role of clouds, both thick and thin, is important in their
effect on energy balance.


Like a giant
cloud, the Moon during the total solar eclipse cast a large shadow across a
swath of the United States. Scientists know the dimensions and light-blocking
properties of the Moon, so they used ground- and space-based instruments to
learn how this large shadow affects the amount of sunlight reaching Earth’s
surface, especially around the edges of the shadow. Measurements from EPIC show
a 10% drop in light reflected from Earth during the eclipse (compared to about
1% on a normal day). That number will help scientists model how clouds radiate the
Sun’s energy – which drives our planet’s ocean currents, seasons, weather and
climate – away from our planet.

even more eclipse science updates, stay tuned to

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