Andromeda is the closest large galaxy to us, 2.5 million light-years from the sun.

Nasa has published the first images from its Wide-field Infrared Survey Explorer, or Wise, which has been scanning the skies since January.

"Wise has worked superbly," said the agency's Ed Weiler in Washington DC.

The images include a comet, a "star factory" 20,000 light years away in our Milky Way galaxy and our nearest large neighbour, the Andromeda spiral galaxy.

Wise will search on until October when its supplies of frozen coolant for chilling instruments will run out.

Comet Siding Spring could provide clues about the solar system's birth.

It's hoped it will find many more comets and, from them, provide information about the birth of our Solar System. It's also looking for asteroids and cool stars called brown dwarfs.

By the time the mission ends the explorer should have scanned the sky one-and-a-half-times with its "infrared goggles", revealing objects not visible to the naked eye.

"All these pictures tell a story about our dusty origins and destiny," said Peter Eisenhardt, Wise project director at Nasa in California.

"Wise sees dusty comets and rocky asteroids tracing the formation and evolution of our solar system. We can map thousands of forming and dying solar systems across our entire galaxy.

"We can see patterns of star formation across other galaxies, and waves of star-bursting galaxies in clusters millions of light years away," he explained.