NASA's Parker Solar Probe, which will fly closer to the Sun that any other spacecraft has attempted before is set to explore the corona, a region of the Sun only seen from Earth when the Moon blocks out the Sun's bright face during total solar eclipses.
The launch of the car-sized probe aboard a massive Delta IV-Heavy rocket lit the night sky at Cape Canaveral, Florida at 3:31 am. The spacecraft will fly through the sun's outer atmosphere, the super-hot corona.
A Saturday morning launch attempt was foiled by last-minute technical trouble.
Altogether, it will make 24 close approaches over the next seven years.
Thousands of spectators jammed the launch site, including 91-year-old astrophysicist Eugene Parker for whom the spacecraft is named.
In particular, it is hoped to give scientists a greater understanding of solar wind storms that have the potential to knock out the power on Earth. It has been outfitted with a heat shield created to keep its instruments at a tolerable 85 degrees Fahrenheit (29 degrees Celsius) even as the spacecraft faces temperatures reaching almost 2,500 degrees Fahrenheit (1,370 degrees Celsius) at its closest pass.
Although the probe itself is about the size of a vehicle, a powerful rocket is needed to escape Earth's orbit, change direction and reach the sun.
But then, the launch of NASA's Mariner 2 spacecraft in 1962 - becoming the first robotic spacecraft to make a successful planetary encounter - proved them wrong. The Parker Solar Probe is completely dependent on its directional heat shield for survival.More news: United States military to create ‘Space Force’ by 2020
Physicist Eugene Parker watches the launch of the spacecraft that bears his name - NASA's Parker Solar Probe - early in the morning of August 12, 2018.
An artist's depiction of the Parker Solar Probe at work around the sun.
"What's so cool about all of this is hanging out with Parker and seeing his emotion", Zurbuchen said, adding that Parker went from being excited about the launch to being excited about the science to come.
Greeting the launch - on the back of a mammoth Delta-IV Heavy rocket - NASA tweeted: "3-2-1... and we have liftoff of Parker #SolarProbe atop @ULAlaunch's #DeltaIV Heavy rocket".
At this point, the probe will be moving at roughly 700,000 kilometres per hour, setting the record for the fastest-moving object made by humanity.
"To protect itself, the spacecraft has a thermal protection system, or heat shield, that will provide a shadow in which the spacecraft will "hide" to perform its scientific data gathering".
The probe will make its closest approach in 2024 when the next total solar eclipse is expected to be seen over the US, and with that, the spacecraft will be visible.
Perhaps most important for us humans, the science undertaken with the help of the Parker Solar Probe will likely improve our ability to forecast space weather - including solar flares that can disrupt signals from satellites and, in extreme cases, can even blow out transformers on our terrestrial power grids.