People across Suffolk reported seeing a strange glowing triangle in the sky last night, with many jumping to the conclusion that it was a UFO.

At around 10pm stargazers began to post on social media about the mysterious object in the sky.

One Facebook user asked if it "could have been the spotlight of an Apache helicopter through the clouds", while others checked flight radar to see if they could identify the object.

But now it has been confirmed that the mysterious triangle was a NASA rocket slowing down before it re-entered the atmosphere.

East Anglian Daily Times: The Rocket was sighted across SuffolkThe Rocket was sighted across Suffolk (Image: Nick Lingard)

The American Atlas V Rocket had been launched from Vanderberg Space Force base in California earlier that day.

The 590 ton, 58 meter tall rocket was designed by Lockheed Martin and operated by United Launch Alliance.

On board the rocket was Landsat 9, a NASA satellite launched into orbit to observe the land surface of the Earth.

The satellite is used for monitoring landscapes across the world, including observing deforestation, urban expansion and glacial retreat. It is the latest in a 50 year history of the program.

According to the mission website: "Landsat 9 will extend our ability to measure changes on the global land surface at a scale where we can separate human and natural causes of change.

"When land use and resource availability issues arise, Landsat 9 will help decision makers make informed management decisions.

"Landsat 9 will thus contribute a critical component to the international strategy for monitoring the health and state of the Earth."

East Anglian Daily Times: The engine plume of the centaur upper stage from the Landsat mission was seen as it deorbited itself to avoid becoming space junk seen over East AngliaThe engine plume of the centaur upper stage from the Landsat mission was seen as it deorbited itself to avoid becoming space junk seen over East Anglia (Image: Aaron Fickling)

The satellite was successfully delivered into orbit — the photographs show the rocket's upper stage burning its engines in order to bring itself back into the atmosphere, where it can be safely burnt up.

NASA does this with spacecraft to avoid space junk, which can be dangerous for both satellites and manned missions.