Nasa is set to make a big announcement about its first ever mission to "touch the Sun". The space agency will announce the launch of a solar probe that will fly "directly into our Sun's atmosphere".

Nasa will announce its Solar Probe Plus mission on Wednesday (31 May). The probe is expected to face heat and radiation unlike any other spacecraft ever before, since it will be orbiting within four million miles of the Sun's surface.

The live event will be broadcast NASA TV at 16:00 BST.

"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. The resulting data will improve forecasts of major space weather events that impact life on Earth, as well as satellites and astronauts in space," Nasa said in a statement.

With the Solar Probe Plus mission, Nasa is looking to break its own record of inching ever closer to the Sun. In 1976, Helios 2, the second spacecraft to be launched by the space agency to study the Sun, flew as close as around 43 million km to the surface of the Sun. In contrast, Nasa's new mission will delve a lot deeper.

Nasa's new mission is slated to launch in the summer of 2018. The probe will fly past Venus seven times over the course of almost seven years as it gradually settles into its orbit around the Sun. Although the spacecraft will be protected with a 4.5in-thick carbon composite shield, it will face temperatures as high as nearly 2,500F (1,377C).

More details about the mission are likely to be revealed soon, when Nasa officially announces the Solar Probe Plus mission.