The mission had been expected to launch on Saturday, but was delayed at the last minute due to a technical problem. Scientists aim to learn more about the mechanisms that power the solar wind of charged particles the sun sends into the solar system, creating aurorae on Earth and sometimes screwing with our tech.
After plunging into the Sun's atmosphere, the probe will be using seven Venus flybys to steadily reduce into its orbit.
It is protected by an ultra-powerful heat shield that can endure unprecedented levels of heat, and radiation 500 times that experienced on Earth.
Among them are the FIELDS suite that measures the electric and magnetic fields around the spacecraft and SWEAP that counts particles in the solar wind and measures their velocity, density and temperature.
According to NASA, the mission to reach the sun's atmosphere will take about seven years.
Rocket maker United Launch Alliance said it would try again Sunday, provided the helium-pressure issue can be resolved quickly.
The mission is named for Eugene Parker, the physicist who first theorized the existence of the solar wind in 1958.
Among the mysteries scientists hope to solve: Why is the corona hundreds of times hotter than the surface, which is 5,500 degrees Celsius?
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The US space agency NASA has launched a probe that that will get closer to the Sun than any manmade object has ever done before.
When it nears the Sun, the probe will travel at some 430,000 miles per hour (692,000 kilometers per hour).
Scientists have wanted to build a spacecraft like this for more than 60 years, but only recently did the heat shield technology capable of protecting sensitive instruments become available. It is set to fly into the Sun's corona within 3.8 million miles (6.1 million km) of the solar surface, seven times closer than any other spacecraft.
NASA's science mission chief, Thomas Zurbuchen, was thrilled not only with the launch, but Parker's presence.
NASA launched its Parker Solar Probe at 3:31 a.m.
It was the first rocket launch ever witnessed by Parker, a retired University of Chicago professor.
These explosions create space weather events that can pummel Earth with high energy particles, endangering astronauts, interfering with Global Positioning System and communications satellites and, at their worst, disrupting our power grid.
By the time Parker gets to its 22nd, 23rd and 24th orbits of the sun in 2024 and 2025, it will be even deeper into the corona and travelling at a record 430,000 miles per hour (690,000 kph). The spacecraft will transmit its first science observations in December, beginning a revolution in our understanding of the star that makes life on Earth possible.