February 10, 2020 5:23:25 pm
Written by Kenneth Chang
A rocket carrying Solar Orbiter, a probe that will take pictures of the top and bottom of the sun, launched Sunday night. The Atlas 5 rocket launched on time, just as the final Oscar statues were being handed out for the 2020 Academy Awards, and illuminated the night sky over Florida’s Atlantic coast as it headed away from Earth to place the Solar Orbiter spacecraft into an orbit around the sun.
A new view of the sun
With Solar Orbiter, scientists will for the first time get a good view of the top and bottom of the sun. Until now, almost all of the solar-watching spacecraft have orbited in the ecliptic, or the same plane that the planets travel around the sun.
That change of view could help solve mysteries about how the sun spews high-velocity charged particles that fly outward through the solar system and buffet the planets, including Earth. The magnetic fields that accelerate those particles flow into and out of the sun’s poles. The data from Solar Orbiter could help explain the sunspot cycle — Why does the cycle last 11 years? Why are some quiet and others roar violently? — and help models to predict solar storms that could disrupt Earth’s power grids and satellites in orbit.
Ulysses, an earlier collaboration between NASA and the European Space Agency launched in 1990, also passed over the sun’s poles, but at much farther distances, and it did not carry a camera.
A long and winding journey
The launch trajectory will take Solar Orbiter away from Earth into an orbit around the sun. A flyby of Venus on the day after Christmas will sap some of its energy and let it spiral closer toward the sun.
Additional flybys — one of Earth, two more of Venus — will further adjust the orbit, which will still be in the ecliptic, the plane of the orbits.
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 mission is expected to complete 22 orbits of the sun in 10 years.
Solar Orbiter’s instruments
The spacecraft’s 10 scientific instruments are a mix. 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.
Remember the caution that you should not look directly at the sun? Solar Orbiter’s cameras have to do just that, and at a distance where the sunlight is 13 times as intense. Three peepholes in the heat shield will open for 10 days at a time 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. The coronagraph includes a disk to block out most of the light to look at what is going on in the sun’s outer atmosphere.
Magnetic fields and solar storms
Occasionally, the sun erupts giant amounts of particles known as coronal mass ejections. When such an eruption slams into Earth’s magnetic field, it generates surges of electrical current.
Solar scientists do not have reliable ways to predict such an eruption. The largest one known to hit Earth was the Carrington event in 1859, named after one of the people who observed an intensely bright spot on the sun where the eruption occurred. The surge caused some telegraph wires to catch fire.
When Nicola J. Fox, director of NASA’s heliophysics division, talks about solar science to children at schools, she introduces the Carrington event and how it knocked out the telegraph system in the U.S. for four days.
“The kids just kind of look at me like, ‘So what?’,” she said. “And then I say, ‘Imagine you didn’t have your iPad for four days.’ Panic ensues in the classroom.”
A similar event today could potentially cause not only continentwide blackouts, but also destroy giant transformers on the electric grid — damage that might take months or years to repair.
A smaller solar storm in March 1989 knocked out power in Quebec for nine hours. Just a few years ago, Earth was lucky.
On July 23, 2012, NASA’s Stereo-A spacecraft was hit by a gigantic coronal mass ejection. Analysis showed that this outburst was bigger than the Carrington eruption. If Earth had been where Stereo-A was — the spacecraft travels in the same orbit as Earth, but ahead of the planet — that would have been a very interesting day.
A partnership with Parker Solar Probe
In 2018, NASA launched the 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. That probe is flying into the sun’s outer atmosphere, known as the corona, and eventually coming within 4 million miles of its surface. By comparison, Earth is 93 million miles from the sun. Mercury, the closest planet, is 29 million miles from the sun.
The close distance allows the Parker Solar Probe to make direct measurements of those regions, but it has to be protected from temperatures of about 2 million degrees Fahrenheit.
Solar Orbiter will be passing farther from the sun. At the closest point along its elliptical orbit, it will be just 3 million miles inside of the orbit of Mercury, and experience much less extreme temperatures. Instead of millions of degrees, temperatures at Solar Orbiter will reach several hundred degrees. That allows Solar Orbiter to carry a wider range of instruments.
Coordinated observations between Parker and Solar Orbiter could identify phenomena on the surface with conditions in the corona.
“It’s really a perfect dream, a marriage in heaven,” said Guenther Hasinger, director of science at European Space Agency during a news conference Friday.
A slightly less busy rocket day
Solar Orbiter was not the only spacecraft scheduled to be launched from the East Coast on Sunday. A crewless Antares cargo ship with supplies, equipment and experiments destined for International Space Station was to lift off at 5:39 p.m. Eastern time from the Mid-Atlantic Regional Spaceport in Virginia. However, after a short postponement, Sunday’s launch was called off. Northrop Grumman, which manages the Antares and Cygnus flights, described a problem with a sensor on the ground. It said it will not be able to attempt a launch again until Thursday because of weather concerns as well as time needed to address the problem that caused the scrubbed launch.
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