The sun, the very centerpiece of our solar system and the most important source of energy for life on Earth, has a visitor.
On Oct. 29, NASA's Parker Solar Probe achieved a milestone by becoming the closest man-made object to the sun. The previous record was held by the German-US Helios 2 satellite back at 26.55 million miles from the sun. Over the next several years, the probe will orbit closer to the sun with the closest approach being 3.83 million miles away.
Over the course of several days in the beginning on November, the probe completed its first solar encounter phase through the sun's outer atmosphere, the corona.
"Parker Solar Probe is providing us with the measurements essential to understanding solar phenomena that have been puzzling us for decades," said Nour Raouafi, Parker Solar Probe project scientist at the Johns Hopkins University Applied Physics Lab. "To close the link, local sampling of the solar corona and the young solar wind is needed and Parker Solar Probe is doing just that."
Just a couple weeks later on Nov. 16, the probe reported back to mission control at Johns Hopkins Applied Physics Lab that all systems were operating well.
Why this mission is a big deal
The probe was launched on Aug. 12 and is on an unprecedented mission to study some of the sun's biggest secrets. It's named after astrophysicist Eugene Parker, the S. Chandrasekhar Distinguished Service Professor Emeritus in the Department of Astronomy and Astrophysics at the University of Chicago, who discovered the phenomenon now known as solar wind.
"It was a very quiet launch countdown, it went off like clockwork," said Omar Baez, NASA launch director. "Parker Solar Probe has been one of our most challenging missions to date. I’m very proud of the team that worked to make this happen. We at NASA and the Launch Services Program are thrilled to be part of this mission."
"The solar probe is going to a region of space that has never been explored before," said Parker in a statement last year. "It’s very exciting that we’ll finally get a look. One would like to have some more detailed measurements of what’s going on in the solar wind. I’m sure that there will be some surprises. There always are."
This is the first time NASA has named a mission after a living individual, a testament to Parker's vast body of work.
"Placed in orbit within 4 million miles of the sun’s surface, and facing heat and radiation unlike any spacecraft in history, the spacecraft will explore the sun’s outer atmosphere and make critical observations that will answer decades-old questions about the physics of how stars work," NASA said in a 2017 statement. "The resulting data will improve forecasts of major space weather events that impact life on Earth, as well as satellites and astronauts in space."
Unlike the Greek legend Icarus, whose wings melted when he flew too close to the sun, NASA's new spacecraft will come prepared. To protect its instruments from temperatures approaching 2,600 degrees Fahrenheit (1,426 degrees Celsius), the Parker Solar Probe (which was originally named the Solar Probe Plus) features an 8-foot-wide, 4.5-inch-thick carbon-composite foam shield called the Thermal Protection System (TPS).
Unlike traditional armor, TPS weighs only 160 pounds and has an internal structure of 97 percent air. The engineering behind its design is so efficient that those components protected on the shaded side will astoundingly experience nothing more than room temperature. NASA installed the shield in June after it was briefly attached late last year just for testing.
Much like the Cassini spacecraft's series of ever-closer dives toward Saturn, the probe will experience no fewer than 24 close encounters with the sun using repeated gravity assists from Venus. Its most precarious dive through the sun's outer atmosphere, projected to occur in 2024, will have it passing by the sun's surface at a distance of only 3.8 million miles. As a comparison, the closest NASA has ever approached the sun is from a distance of 27 million miles with the Helios 2 spacecraft in 1976.
At that point, the Parker Solar Probe will make history by becoming the fastest man-made object ever. Its closest approach to the sun will send the spacecraft speeding along at a record-breaking 450,000 miles per hour. “That's fast enough to get from Philadelphia to Washington, D.C., in one second,” NASA added.
Exposing the sun's secrets
In addition to sending a spacecraft into uncharted, scorching territory above a star, NASA also has a series of scientific objectives to accomplish. These include a study of the causes behind the sun's wildly different temperatures (i.e., an atmospheric temperature range of 3.5 million F vs. a surface temperature of "only" 10,000 degrees F) and the forces behind its solar wind and energetic particles that impact Earth and the solar system.
"There are a few major mysteries with the sun and the solar wind," SPP project scientist Nicola Fox told Vice. "One is that the corona — the atmosphere that you see around the Sun during a solar eclipse — is actually hotter than the surface of the sun. So, that kind of defies the laws of physics. It just shouldn't happen."
NASA researchers hope that the data gained from this mission will not only enable a greater understanding of how stars like our sun work, but also provide answers that might better protect against potentially catastrophic solar storms.
"Many of the systems we in the modern world rely on — our telecommunications, GPS, satellites and power grids — could be disrupted for an extended period of time if a large solar storm were to happen today," Justin C. Kasper, principal investigator at the Smithsonian Astrophysical Observatory, told Popular Mechanics. "Solar Probe Plus will help us predict and manage the impact of space weather on society."
Editor's note: This story was originally published in May 2017 and has been updated with new information.