STAR-STRUCK astronomers from the University of Hertfordshire have discovered what is possibly the coolest sub-stellar body ever found outside the solar system.

The discovery, a so-called brown dwarf known as SDSS1416+13B, has an estimated temperature of 500 Kelvin, or 227 degrees Celsius.

It was seen through the United Kingdom Infrared Telescope (UKIRT) in Hawaii and is in a wide orbit around a brighter object known as SDSS1416+13A.

What has excited astronomers are the peculiar colours, which make the brown dwarf appear either very blue or very red depending on how it is viewed.

Dr Philip Lucas, from the school of physics, astronomy and mathematics, said: “Even if it turns out that the low temperature is not quite record breaking, the colours are so extreme that this object will keep a lot of physicists busy trying to explain it.

“The colours are so different than anything seen before we don't really understand it yet.”

The brown dwarf is located between 15 and 50 light years from the solar system, which is quite close in astronomical terms, some galaxies have been spotted up to 13 billion light years from Earth.

Brown dwarfs are smaller than stars but larger than giant gas planets, such as Jupiter. Due to their low temperature they are very faint in visible light, and are detected by their infrared glow.

UKIRT, which opened in 1979, is the world's largest dedicated infrared telescope, at 12.5-feet, and sits at an altitude of 13,760 feet above sea level.