Spacecraft
record solar activity as a binary code, 1s and 0s, which computer
programs can translate into black and white. Scientists colorize the
images for realism, and then zoom in on areas of interest. Image Credit: NASA/Karen Fox. Hi-Res Image
Four
of the telescopes on the Solar Dynamics Observatory observe extreme
ultraviolet light activity on the sun that is invisible to the naked
eye. Image Credit: NASA/SDO. Hi-Res Image
The
Solar Dynamics Observatory observed a solar flare (upper left) and a
coronal mass ejection (right) erupting from the sun’s limb in extreme
ultraviolet light on August 6, 2010. Image Credit: NASA/SDO. Hi-Res Image
You
cannot look at the sun without special filters, and the naked eye
cannot perceive certain wavelengths of sunlight. Solar physicists must
consequently rely on spacecraft that can observe this invisible light
before the atmosphere absorbs it.
“Certain wavelengths either do not make it through Earth’s atmosphere
or cannot be seen by our eyes, so we cannot use normal optical
telescopes to look at the spectrum,” said Dean Pesnell, the project
scientist for the Solar Dynamics Observatory, or SDO, at NASA’s Goddard
Space Flight Center in Greenbelt, Maryland.
Several spacecraft can observe these invisible light wavelengths. SDO
for example has four telescopes that image the sun in the ultraviolet
spectrum. As beams of ultraviolet light pass into the telescope, a
mirror with special coatings filters and amplifies the ultraviolet
light’s otherwise poor reflection. The incoming photons are then
recorded as pixels and converted into electrical signals, similar to how
your cell phone camera sees visible light.
“It’s exactly the same process, whether it’s ultraviolet light,
infrared light, visible light, or radio,” said Joseph Gurman, project
scientist for both the Solar and Heliospheric Observatory and the Solar
Terrestrial Relations Observatory at Goddard. “In this case we’re trying
to understand how the sun changes and how those changes affect life
here on Earth.”
Ultraviolet light causes molecular radiation damage to our skin, seen
as sunburns that can lead to cancer. Its cousin, extreme ultraviolet
radiation, and the associated solar storms have the potential to disrupt
communications and spacecraft navigation. “These are very damaging,
energetic photons, and we want to understand what chain of events
produces these photons,” Pesnell said.
Thankfully our planet’s atmosphere absorbs much of this solar
radiation, making life on Earth possible.
However, this means that to
study extreme ultraviolet light, instruments must do it from the vacuum
of space.
“Ultraviolet light from the sun can show us the origins of solar
storms that can lead to power outages, cell phone disruptions, and
delays in shipping packages due to the rerouting of planes from over the
pole,” Gurman said.
By understanding what occurs in the sun’s atmosphere, scientists hope
to predict when powerful solar events such as coronal mass ejections
and solar flares may occur.
“You really want to know what’s happening on the sun as soon as you
can,” said Jack Ireland, a solar visualization specialist at Goddard.
“We can then use computer models to estimate how solar events will
affect Earth’s space environment.”
The information can then be used by NOAA’s Space Weather Prediction
Center, in Boulder, Co. to alert power companies and airlines to take
the necessary precautions, thus avoiding power outages and keeping
airplane passengers safe.
