First images from the National Science Foundation’s Daniel K. Inouye
Solar Telescope reveal unprecedented detail of the sun’s surface and preview
the world-class products to come from this preeminent 4-meter solar telescope.
NSF’s Inouye Solar Telescope, on the summit of Haleakala, Maui, in Hawai’i,
will enable a new era of solar science and a leap forward in understanding the
sun and its impacts on our planet.
Activity on the
sun, known as space weather, can affect systems on Earth. Magnetic eruptions on
the sun can impact air travel, disrupt satellite communications and bring down
power grids, causing long-lasting blackouts and disabling technologies such as
GPS.
The first images
from NSF’s Inouye Solar Telescope show a close-up view of the sun’s surface, which
can provide important detail for scientists. The images show a pattern of
turbulent “boiling” plasma that covers the entire sun. The cell-like structures
— each about the size of Texas — are the signature of violent motions that
transport heat from the inside of the sun to its surface. That hot solar plasma
rises in the bright centers of “cells,” cools, then sinks below the surface in
dark lanes in a process known as convection.
“Since NSF began
work on this ground-based telescope, we have eagerly awaited the first images,”
said France Córdova, NSF director. “We can now share these images and videos,
which are the most detailed of our sun to date. NSF’s Inouye Solar Telescope
will be able to map the magnetic fields within the sun’s corona, where solar eruptions
occur that can impact life on Earth. This telescope will improve our
understanding of what drives space weather and ultimately help forecasters
better predict solar storms.”
Expanding knowledge
The sun is our nearest star — a gigantic nuclear reactor that burns
about 5 million tons of hydrogen fuel every second. It has been doing so for
about 5 billion years and will continue for the other 4.5 billion years of its
lifetime. All that energy radiates into space in every direction, and the tiny
fraction that hits Earth makes life possible. In the 1950s, scientists figured
out that a solar wind blows from the sun to the edges of the solar system. They
also concluded for the first time that we live inside the atmosphere of this
star. But many of the sun’s most vital processes continue to confound
scientists.
“On Earth, we
can predict if it is going to rain pretty much anywhere in the world very
accurately, and space weather just isn’t there yet,” said Matt Mountain,
president of the Association of Universities for Research in Astronomy, which
manages the Inouye Solar Telescope. “Our predictions lag behind terrestrial
weather by 50 years, if not more. What we need is to grasp the underlying
physics behind space weather, and this starts at the sun, which is what the
Inouye Solar Telescope will study over the next decades.”
The motions of
the sun’s plasma constantly twist and tangle solar magnetic fields . Twisted
magnetic fields can lead to solar storms that can negatively affect our
technology-dependent modern lifestyles. During 2017’s Hurricane Irma, the
National Oceanic and Atmospheric Administration reported that a simultaneous
space weather event brought down radio communications used by first responders,
aviation and maritime channels for eight hours on the day the hurricane made
landfall.
Finally
resolving these tiny magnetic features is central to what makes the Inouye
Solar Telescope unique. It can measure and characterize the sun’s magnetic
field in more detail than ever seen before and determine the causes of
potentially harmful solar activity.
“It’s all about
the magnetic field,” said Thomas Rimmele, director of the Inouye Solar
Telescope. “To unravel the sun’s biggest mysteries, we have to not only be able
to clearly see these tiny structures from 93 million miles away but very
precisely measure their magnetic field strength and direction near the surface
and trace the field as it extends out into the million-degree corona, the outer
atmosphere of the sun.”
Better
understanding the origins of potential disasters will enable governments and
utilities to better prepare for inevitable future space weather events. It is
expected that notification of potential impacts could occur earlier — as much
as 48 hours ahead of time instead of the current standard, which is about 48
minutes. This would allow more time to secure power grids and critical
infrastructure and to put satellites into safe mode.
The engineering
To achieve the
proposed science, this telescope required important new approaches to its
construction and engineering. Built by NSF’s National Solar Observatory and
managed by AURA, the Inouye Solar Telescope combines a 13-foot (4-meter) mirror
— the world’s largest for a solar telescope — with unparalleled viewing
conditions at the 10,000-foot Haleakala summit.
Focusing 13
kilowatts of solar power generates enormous amounts of heat — heat that must be
contained or removed. A specialized cooling system provides crucial heat
protection for the telescope and its optics. More than seven miles of piping distribute
coolant throughout the observatory, partially chilled by ice created on site
during the night.
The dome
enclosing the telescope is covered by thin cooling plates that stabilize the
temperature around the telescope, helped by shutters within the dome that
provide shade and air circulation. The “heat-stop” (a high-tech, liquid-cooled,
doughnut-shaped metal) blocks most of the sunlight’s energy from the main
mirror, allowing scientists to study specific regions of the sun with
unparalleled clarity.
The telescope
also uses state-of-the-art adaptive optics to compensate for blurring created
by Earth’s atmosphere. The design of the optics (“off-axis” mirror placement)
reduces bright, scattered light for better viewing and is complemented by a
cutting-edge system to precisely focus the telescope and eliminate distortions
created by the Earth’s atmosphere. This system is the most advanced solar
application to date.
“With the
largest aperture of any solar telescope, its unique design, and
state-of-the-art instrumentation, the Inouye Solar Telescope — for the first
time — will be able to perform the most challenging measurements of the sun,”
Rimmele said. “After more than 20 years of work by a large team devoted to
designing and building a premier solar research observatory, we are close to
the finish line. I’m extremely excited to be positioned to observe the first
sunspots of the new solar cycle just now ramping up with this incredible
telescope.”
New era of solar astronomy
NSF’s new
ground-based Inouye Solar Telescope will work with space-based solar
observation tools such as NASA’s Parker Solar Probe (currently in orbit around
the sun) and the European Space Agency/NASA Solar Orbiter (soon to be
launched). The three solar observation initiatives will expand the frontiers of
solar research and improve scientists’ ability to predict space weather.
“It’s an
exciting time to be a solar physicist,” said Valentin Pillet, director of NSF’s
National Solar Observatory. “The Inouye Solar Telescope will provide remote sensing
of the outer layers of the sun and the magnetic processes that occur in them.
These processes propagate into the solar system where the Parker Solar Probe
and Solar Orbiter missions will measure their consequences. Altogether, they
constitute a genuinely multi-messenger undertaking to understand how stars and
their planets are magnetically connected.”
“These first
images are just the beginning,” said David Boboltz, a program director in NSF’s
Division of Astronomical Sciences who oversees the facility’s construction and
operations. “Over the next six months, the Inouye telescope’s team of
scientists, engineers and technicians will continue testing and commissioning
the telescope to make it ready for use by the international solar scientific
community. The Inouye Solar Telescope will collect more information about our
sun during the first 5 years of its lifetime than all the solar data gathered
since Galileo first pointed a telescope at the sun in 1612.”
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