This weekend, in the dark hours before dawn, NASA plans to send a spacecraft to touch the sun.
The Parker Solar Probe, which could blast off from Cape Canaveral Air Force Station as early as 3:33 a.m. Saturday, will dip down to within 4 million miles of the solar surface _ or nearly 10 times as close as sun-scorched Mercury.
Each of its 24 orbits will provide an extraordinary glimpse at the sun’s ethereal corona and offer a taste of the solar wind.
Each pass also comes with terrible risk, forcing the spacecraft to face powerful electric and magnetic fields, speeding-bullet dust grains and obliterating heat.
The years of work building a spacecraft tough enough to survive this environment — and sophisticated enough to send back valuable data — are well worth the effort, scientists say.
“We’re going to explore unknown territory,” said Marco Velli, a UCLA space physicist and the probe’s observatory scientist.
“People are hugely excited about this,” said Robert Rosner, a computational physicist at the University of Chicago who was not involved in the mission. Talk of such a solar probe, he said, “probably goes back at least 40 years.”
The Parker spacecraft seeks to answer fundamental questions about our nearest star that have stymied space physicists for decades.
Among them: Why does the corona — the ghostly halo of plasma, or ionized gas, surrounding the sun — reach temperatures higher than 2 million degrees Fahrenheit, hundreds of times hotter than the sun’s broiling surface? And what powers the solar wind, the stream of charged particles that flows outward from the corona at speeds on the order of a million mph?
No human efforts to study our home star _ telescopes that scan the surface, X-ray observations of the corona, spacecraft that pass over the poles _ have fully answered these questions, said Justin Kasper, a space scientist at the University of Michigan and leader of a particle-sampling instrument suite.
“We can’t agree on what’s actually going on,” Kasper said. “When you look at what gets to Earth or to these spacecraft, it’s ambiguous.”
The answers that Parker finds would not just help scientists understand the behavior of the sun, Kasper and his colleagues said. They could potentially shed light on coronal structures around massive galaxies, the jets from powerful black holes and accretion disks where young planets are forming.
With a fuller portrait of our sun, scientists may also be able to better shield both our infrastructure as well as future space travelers, said David McComas, a Princeton University space physicist who leads an instrument suite studying energetic particles.
“If you go out to the moon or if you’re planning on going out to Mars or elsewhere, these solar energetic particles provide potentially a very dangerous radiation environment for astronauts,” McComas said.
The Parker probe will get so close that the pressure from mere sunlight will be enough to flip the spacecraft around in less than a minute, Kasper said. And without shielding, most of its instruments would quickly melt. That’s not to mention the remote but still real possibility that high-speed dust particles could slam into the spacecraft from the opposite direction at a relative speed of 400 kilometers per second.
After launch, the spacecraft will head toward Venus, whose gravity will bend its path into the correct orbit. After that late September flyby, the Parker should make its first close approach to the sun on Nov. 1 — the first of about two dozen solar passes and seven gravity assists from Venus. Its final encounter with the sun’s atmosphere will come in June 2025.