A Stroke of Astronomical Luck for Solar Science
Scientists plan for an eclipse over NSF’s observatory in Chile
By Shari Lifson
On July 2, 2019 a total solar eclipse will pass over Chile and Argentina, and through a stroke of astronomical luck, the path of totality crosses directly over the National Science Foundation’s (NSF) Cerro Tololo Inter-American Observatory located in the foothills of the Andes, 7,241 feet (2200 meters) above sea level in the Coquimbo Region of northern Chile. Five science teams chosen by NSF’s National Solar Observatory will perform experiments at Cerro Tololo during the eclipse; four of them will have their equipment trained on the Sun’s elusive corona and one will study eclipse effects on the Earth itself.
The Sun’s Corona
Throughout history, total solar eclipses have amazed humankind. Many cultures’ eclipse myths and legends portray them as divine, fortuitous or even ominous events. Today we understand the science behind why total solar eclipses occur. But we can still learn a lot about the Sun during the brief minutes of totality, when the Sun is completely blocked by the Moon. For scientists, a total solar eclipse offers a rare opportunity to study a part of the Sun they don’t normally see, its inner corona.
The corona is a region of magnetism and extraordinarily hot gasses that makes up the outermost part of the Sun’s atmosphere. It has mysterious properties we have yet to understand, like why it is extremely hot, hotter than the surface of the Sun. It is especially difficult to study because it is less dense and millions of times dimmer than the visible disk of the Sun and thus hard to see in the sun’s full glare. However, when the bright disk of the Sun is completely covered by the Moon, as in a total solar eclipse, we can see its corona shining.
Scientists study the corona because it is important for predicting space weather, a phenomena that can potentially damage our electrical grids, telecommunications and satellites. Space weather occurs when the Sun occasionally spews magnetic plumes called coronal mass ejections into space. If one of those plumes is aimed at Earth, we could experience electrical and telecommunication disruptions like the super solar storm of 1859 known as the Carrington event, that burned up telegraph wires around the world. Such magnetic storms carry a much greater risk today in our electronically connected and dependent world.
Each of the following five science teams are taking advantage of the 2 minutes and 6 seconds of totality on Cerro Tololo to increase our understanding of the Sun’s mysteries and its impact on Earth.
Observations Over 20 Plus Years
An international team led by Jay Pasachoff (Williams College) will image the Sun’s corona as a continuation of an experiment started in the 1990s. The experiment will measure the corona’s current color, shape, and temperature.
Pasachoff explained why he has been doing this experiment for so many years, “The Sun varies from day to day, and also over the 11-year solar cycle. Each glimpse we get of the Sun during a total solar eclipse—only a couple of minutes every 18 months or so—gives us a different set of features to look at. One of our interests is understanding the eruptions on the Sun that could damage all the satellites now orbiting the Earth, so when we measure the speeds of the coronal mass ejections we sometimes see at eclipses, our work has potential major security implications for us on Earth.”
The location of the large coronal structures called streamers – pointy regions that appear in most images of the corona is known for – vary throughout the solar cycle. The 2019 eclipse occurs during a minimum of the 11-year solar cycle, a time when solar eruptions are infrequent and the Sun appears to be calm. Eclipses taking place near solar-cycle minimum, like this one, will provide Pasachoff’s team with a rare view of solar polar plumes – tufts of open magnetic field that emanate from the solar north and south poles, which are hidden from our view by high-latitude streamers at other eclipses. “I’m also looking forward to comparing our observations of the corona taken during the eclipse (and combined in computers subsequently) with predictions that colleagues make before the eclipse based on the Sun’s magnetic field and sunspots over the preceding month,” explains Pasachoff.
The corona’s overall temperature also changes with the 11-year sunspot cycle. The team will use observations of superheated iron to follow the overall temperature of the corona over the sunspot cycle.
Pasachoff added, “We are hopeful that observing from the 7,241 feet (2,200 meters) high altitude of NSF’s Cerro Tololo Inter-American Observatory will give us an especially clear view of the corona.”
Summary:
Scientists plan for an eclipse over NSF’s observatory in ChileOn July 2, 2019 a total solar eclipse will pass over Chile and Argentina, and through a stroke of astronomical luck, the path of totality crosses directly over the National Science Foundation’s (NSF) Cerro Tololo Inter-American Observatory located in the foothills of the Andes, 7,241 feet (2200 meters) above sea level in the Coquimbo Region of northern Chile. Five science teams chosen by NSF’s National Solar Observatory will perform experiments at Cerro Tololo during the eclipse; four of them will have their equipment trained on the Sun’s elusive corona and one will study eclipse effects on the Earth itself. The Sun’s CoronaThroughout history, total solar eclipses have amazed humankind. Many cultures’ eclipse myths and legends portray them as divine, fortuitous or even ominous events. Today we understand the science behind why total solar eclipses occur. But we can still learn a lot about the Sun during the brief minutes of totality, when the Sun is completely blocked by the Moon. For scientists, a total solar eclipse offers a rare opportunity to study a part of the Sun they don’t normally see, its inner corona.The corona is a region of magnetism and extraordinarily hot gasses that makes up the outermost part of the Sun’s atmosphere. It has mysterious properties we have yet to understand, like why it is extremely hot, hotter than the surface of the Sun. It is especially difficult to study because it is less dense and millions of times dimmer than the visible disk of the Sun and thus hard to see in the sun’s full glare. However, when the bright disk of the Sun is completely covered by the Moon, as in a total solar eclipse, we can see its corona shining.Scientists study the corona because it is important for predicting space weather, a phenomena that can potentially damage our electrical grids, telecommunications and satellites. Space weather occurs when the Sun occasionally spews magnetic plumes called coronal mass ejections into space. If one of those plumes is aimed at Earth, we could experience electrical and telecommunication disruptions like the super solar storm of 1859 known as the Carrington event, that burned up telegraph wires around the world. Such magnetic storms carry a much greater risk today in our electronically connected and dependent world.Each of the following five science teams are taking advantage of the 2 minutes and 6 seconds of totality on Cerro Tololo to increase our understanding of the Sun’s mysteries and its impact on Earth.VER VERSION EN ESPAÑOL
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