A Moment in the Sun’s Atmosphere: NASA’s Science During the March 2016 Total Solar Eclipse
As the moon slowly covers the face of the sun on the morning of March 9, 2016, in Indonesia, a team of NASA scientists will be anxiously awaiting the start of totality – because at that moment, their countdown clock begins. They plan to take 59 several-second exposures of the sun in just over three minutes, capturing data on the innermost parts of the sun’s volatile, superhot atmosphere – a region we can only observe during total solar eclipses when the sun’s overwhelmingly bright face is completely blocked by the moon.
“The sun’s atmosphere is where the interesting physics is,” said Nelson Reginald, one of several space scientists from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who will conduct an experiment in Indonesia during March 2016’s total solar eclipse. “A total solar eclipse gives us the opportunity to see very close to the solar limb.”
The lower part of the sun’s atmosphere, the corona, is one of the most scientifically interesting areas of the sun. It’s thought to hold the keys to several solar mysteries, from the acceleration of the solar wind, to the birth of explosive clouds of solar material called coronal mass ejections, to the mysterious heating of the corona as a whole. Using a new instrument, the NASA science team will observe aspects of polarized light that carry information about the temperature and velocity of electrons in the lower corona.
Though it’s about as bright as the full moon, the corona is ordinarily drowned out by the sun’s much brighter face, except during total solar eclipses. To study the corona outside of total solar eclipses, scientists use instruments called coronagraphs, which create artificial eclipses by using solid disks to block sun’s bright face and reveal the comparatively faint corona. But because light bends around sharp edges – a phenomenon known as diffraction – coronagraph disks obscure the inner corona, as well as the solar surface, to combat this effect.
“You can’t see the corona that close to the surface with a coronagraph. You cut off a large portion of the innermost corona,” said Nat Gopalswamy, principal investigator of the eclipse experiment at Goddard. “The main advantage of the total solar eclipse is seeing much closer to the sun’s surface.”
The team will use their three minutes of totality to examine the polarized light coming from the sun’s inner corona, light that contains information about the temperature and velocity of the electrons there. Light is polarized when its electric field oscillates along one axis, for instance, up-and-down or side-to-side. Unlike dust, electrons mainly scatter polarized light, meaning that isolating the polarized light can give information about the temperature and flow speed of coronal electrons. Polarized light scattered by these electrons dominates in the regions of the corona closest to the solar surface – so total solar eclipses are our best chance to gather this information.
“We first used this instrument during the 1999 total solar eclipse in Turkey,” said Reginald.
The minutes-long timeframe of total solar eclipses limits the amount of data we can collect during our occasional glimpses at the inner corona, so the team rebuilt their instrument over the last year to make it even faster.
“Before, we would have had use a polarizer that would turn through three angles for each wavelength filter,” said Reginald. “The new polarization camera eliminates the need for a polarization wheel.”
Rather than using a hand-turned polarization wheel to take three separate images in each polarized direction, the new camera uses thousands of tiny polarization filters to read light polarized in different directions simultaneously. Each pixel in the new camera is made of four subpixels with differently-oriented polarization filters, which provides the team with four separate but simultaneous images of the corona and cuts out the need to change polarization filters between exposures.
“We’ve cut down the length of time required for our experiment by more than 50 percent,” said Gopalswamy. “The polarization camera is faster and less risky, because it’s one less moving part.”
Though the team will be performing the experiment for the first time in the province of North Maluku, Indonesia – chosen for its accessibility and high chances of clear skies during the eclipse – they’ve already given their updated instrument a test run.
“The brightness of the full moon is about equal to the brightness of the total solar eclipse,” said Reginald. “So we set up our telescope in the parking lot for practice.”
In partnership with Exploratorium, NASA TV will be showing a live stream of the eclipse on March 8, 2016, from 8-9 pm ET.
Total solar eclipse coming next week to Asia and the Pacific
A total eclipse of the sun will turn day into night over portions of Southeast Asia and the Pacific Ocean next week.
Indonesia will get the best view Wednesday, especially in central portions of Borneo and Sumatra. Most of the solar eclipse will be over the open ocean of the Pacific.
A total solar eclipse occurs when the moon gets in the way of the sun, casting its shadow on the Earth's surface.
A partial solar eclipse, when only some of the sun is covered up, will be visible in many other areas, including China, the Koreas, Japan, the Philippines, Australia and portions of Hawaii.
In Honolulu, 63% of the sun will be covered, according to Sky and Telescope, but because of the International Date Line, Hawaiians will see the event Tuesday afternoon. The maximum eclipse will occur about an hour before sunset at 5:37 p.m. local time Tuesday.
This is the first of two solar eclipses this year, according to NASA. The other will be an "annular" solar eclipse over Africa on Sept. 1. An annular eclipse is one in which the edge of the sun is still visible as a bright ring around the moon.
Folks in the U.S. will have to wait until Aug. 21, 2017, to see the next total solar eclipse. That one will be seen in the Southeast, the Central Plains and the Northwest.
There will be two lunar eclipses this year, on March 23 and Sept. 16, NASA reports. Only the March 23 eclipse will be visible in North America.
Both will be less-spectacular "penumbral" lunar eclipses, when the moon is in Earth’s faint outer (penumbral) shadow. These types of lunar eclipses can almost pass unnoticed.
Quelle: USA TODAY
What NASA Can Learn From the March 9 Eclipse
On Wednesday, March 9, those lucky enough to find themselves within a few hundred miles of Indonesia will be treated to a total solar eclipse, a relatively rare space event in which the moon completely blocks out the sun during its transit.
Beautiful in their own right, total solar eclipses also provide a great opportunity to study the Sun in ways that are only possible when the moon is in the way. Although the Sun will be almost totally obscured by the moon, the Sun’s atmosphere, or corona, will still be visible as a ring around the moon, and this is what’s got space scientists at NASA all fired up about next week’s eclipse.
The Sun’s corona extends millions of miles into space, although it is the inner corona that is of particular interest to astronomers since it is believed to hold the keys to all sorts of solar mysteries, such as the acceleration of solar wind, the generation of coronal mass ejections (explosive clouds of plasma), and the heating of the corona as a whole (which is hundreds of times hotter than the surface of the Sun).
“The sun’s atmosphere is where the interesting physics is,” Nelson Reginald, one the space scientists from NASA’s Goddard Space Flight Center who will be in Indonesia for the eclipse, said in a press release. “A total solar eclipse gives us the opportunity to see very close to the solar limb.”
The corona is technically always visible, but it is about a million times less bright than the Sun’s face (or about as bright of the moon) so it’s usually lost in the light. To study the corona when there’s no eclipse, space scientists usually make use of a coronagraph, which creates artificial eclipses by using an opaque disk to block the Sun’s face. While this works great for studying the outer corona, the coronagraphs are unable to reveal the inner corona. This is because light bends around sharp edges—a phenomenon known as diffraction—so in order to combat this effect, coronagraph disks obscure the inner corona as well as the Sun’s face.
That means that the only time to study the inner corona is for a precious few minutes approximately every 18 to 24 months during a total solar eclipse. And this time around, NASA doesn’t intend to waste a second.
Alaska Airlines changes Anchorage-Honolulu flight to catch total solar eclipse
The flight path for Flight 870 intersects the path of totality for Tuesday’s eclipse. (Credit: Alaska Airlines)
Now, that’s service: Amateur astronomers persuaded Seattle-based Alaska Airlines to shift its departure time for Tuesday’s flight from Anchorage to Honolulu 25 minutes later so that passengers can see a total solar eclipse en route.
“It’s an unbelievably accommodating gesture,” Mike Kentrianakis, solar eclipse project manager for the American Astronomical Society, said in an Alaska Airlines blog post about the schedule shift. “Not only is Alaska Airlines getting people from Point A to Point B, but they’re willing to give them an exciting flight experience.”
Thanks to the time change, the passengers on Alaska Flight 870 are now due to see a minute and 53 seconds of totality out the window from a height of 37,000 feet, well above any clouds. (But if you haven’t bought a ticket, don’t bother looking; the flight’s sold out.)
The maneuver was engineered by Joe Rao, an associate astronomer at the American Museum of Natural History’s Hayden Planetarium as well as a columnist for Space.com and meteorologist for News 12 Westchester in New York.
Rao started making plans to catch this week’s eclipse a year ago, but he worried that the view from Indonesia or Micronesia might be clouded out during monsoon season. So he checked to see if any commercial airline flights intersected with the narrow path of totality. Flight 870 was the one that stuck out. Only problem was, the plane would pass through too early.
Watch the total solar eclipse online – and get ready for 2017’s big one
He and other astronomers took their case for delaying the departure to Alaska Airlines, and the schedule planning team decided to make it happen. Thanks to discussions with air traffic controllers, the Alaska crew will have the flexibility to change their course en route to Honolulu to keep their date with the eclipse.
Rao and about a dozen other astronomers booked seats on the flight months ago, but many of the other Hawaii-bound passengers may not know what’s coming. The astronomers are bringing along hundreds of eclipse-filter glasses so everyone on the plane can watch the eclipse’s partial phase safely. (The glasses won’t be needed during totality.)
“We on the Alaska Airlines flight will be the last people in the world to see this eclipse,” said Craig Small, a semi-retired astronomer at the American Museum of Natural History who booked 7F, a window seat. “Nobody will see it after us.”
Solar Eclipse Over the South Pacific Ocean
During the afternoon of March 9, 2016, a total solar eclipse was visible in parts of southeast Asia and a partial eclipse was visible in parts of Alaska, Hawaii, Guam, and America Samoa. An eclipse occurs when the moon passes directly between Earth and the sun. When the moon's shadow falls on Earth, observers within that shadow see the moon block a portion of the sun's light.
The MODIS instrument on NASA's Aqua satellite captured this image of the total solar eclipse moving across the south Pacific Ocean at 03:05 UTC on March 9, 2016. NASA's Terra satellite also imaged the eclipse on the morning of March 9 at 01:40 UTC.
Image Credit: NASA Goddard MODIS Rapid Response Team