>>Kenneth Chang, The New York Times
Published: 2020-07-17 17:49:12 BdST
“We’ve never been closer to the sun with a camera,” Daniel Müller, the project scientist for the mission, Solar Orbiter, said during a news conference held Thursday by the European Space Agency. “And this is just the beginning of the long epic journey of Solar Orbiter.”
The miniature solar flares, which the scientists call campfires, were seen as the spacecraft made its first close approach to the sun. It came within 48 million miles of the sun’s surface, which is just a bit more than half the distance between Earth and the sun.
The campfires are about one-millionth or one-billionth the size of flares that have been observed from Earth. The sun is in the quiet part of its 11-year-solar cycle, and the surface looks placid.
“But then when you look at it at high resolution, it’s amazing, in the smallest details, how much stuff is going on there,” said David Berghmans of the Royal Observatory of Belgium, principal investigator of an instrument that takes high-resolution images of the lower layers of the sun’s atmosphere. “We couldn’t believe this when we first saw this. And we started giving it crazy names like campfires and dark fibrils and ghosts and whatever we saw.”
Solar Orbiter is a joint mission between the Europeans and NASA, which paid for the rocket that took the probe to space.
One of the spacecraft’s other instruments measures the magnetic field near the surface of the sun.
And it was already able to observe an active region on a part of the surface that is not visible from Earth.
“That’s exciting because we know that the magnetic field is a kind of holistic feature of the sun,” said Sami Solanki of the Max Planck Institute for Solar System Research, the principal investigator of that instrument. “It spreads through the atmosphere and connects very different parts of the sun with each other.”
With the new views, “we’re starting to see the whole beast,” Solanki said.
Coronagraphs captured by the European Space Agency’s solar orbiter. The coronagraphs — pictures that block out the sun’s radiance to observe more clearly the fainter atmosphere of the sun — show visible light, in green, and ultraviolet light, in red. The New York Times
That change of view could help solve mysteries about the sun’s magnetic fields and how they accelerate those solar wind particles. The data from Solar Orbiter could help explain the sunspot cycle — Why does the cycle last 11 years? Why are some quiet while others roar violently? — and help models to predict solar storms that could disrupt Earth’s power grids and satellites in orbit.
For now, the spacecraft remains in the ecliptic, even as flybys of Earth and Venus allow it to spiral inward. The first round of data demonstrates the spacecraft and instruments are working as designed.
“It was really much better than what we, perhaps had not expected, but what we dared to hope for,” Berghmans said.
As the spacecraft spirals inward over the next two years, it will be 26 million miles from the sun’s surface at its closest approach, or not much more than one-quarter of the distance between Earth and the sun.
A flyby of Venus in 2025 will swing Solar Orbiter out of the ecliptic to an angle of 17 degrees. That is enough to get a good glimpse of the polar regions. Additional Venus flybys will increase the angle to 33 degrees.
The spacecraft carries 10 scientific instruments. Some measure what is happening directly around the spacecraft, like the magnetic fields and particles of the solar wind. Others take pictures of what is occurring on the sun.
As the orbiter approaches the sun, three peepholes in the heat shield will open to allow the instruments to collect data. The assorted cameras also have heat-resistant windows (think of them as scientific sunglasses) as protection.
The cameras will look at a range of wavelengths of light, including ultraviolet and X-rays. Some of the cameras break the light into separate wavelengths to identify specific molecules. One instrument, the coronagraph, includes a disk to block out most of the light and only look at what is going on in the sun’s outer atmosphere, or corona, which can be observed during a total solar eclipse.
Solar Orbiter is not the only spacecraft studying our planet’s star. Ten other missions in space also keep an eye on the sun and the solar wind. The most recently launched, in 2018, is NASA’s Parker Solar Probe, which is making closer and closer flybys of the sun as it reaches the fastest speeds ever achieved by a human-built spacecraft. It will fly within 4 million miles of the sun’s surface, allowing direct measurements of the corona and other solar regions.
“As far as taking high-resolution images goes, there are two options: getting closer to the object of interest or building a better bigger telescope,” Müller said. “That’s a little bit like going on an expedition. You either get closer to the elephant or you use a bigger camera.”
Solar Orbiter is the equivalent of getting closer to the elephant.
Back on Earth, astronomers are taking the bigger camera approach. While there is much that ground-based telescopes cannot see because the Earth’s atmosphere blocks swaths of the sunlight in the X-ray and ultraviolet wavelengths, the instruments do help advance solar science. The first images from the 4-meter-wide Daniel K. Inouye Solar Telescope in Hawaii, released in January, show the sun’s face divided up into kernel-like cells that look almost like bubbles of caramel erupting on a stovetop.
© 2020 New York Times News Service