A mysterious, deep red point of light that might turn out to be by far the most distant object ever seen has astronomers baffled.
The object, dubbed HDFN-JD1 by its discoverers, has been found in a corner of the sky that was picked out by the Hubble space telescope for its deepest images of the distant universe in 1995.
However, it is invisible at optical wavelengths and has only been seen in the infrared with Hubble's Nicmos camera and with telescopes at the Kitt Peak National Observatory and the Keck Observatory.
No other object in the Hubble Deep Field has appeared so deeply red.
One possible explanation for its colour being explored by scientists is that it has an unprecedented high red shift - an indication of how fast it is moving away from the Earth and hence how far away it is.
While most observed galaxies have a red shift of up to 4, initial calculations by Mark Dickinson and colleagues at the Space Telescope Science Institute in the US put HDFN-JD1's at 12.5. If confirmed, this would dwarf the newly announced discovery by the Sloan Digital Sky Survey of a quasar with a red shift of 5.8. Scientists would be looking at one of the first objects to form in the infant universe. Dr Dickinson said there was as yet no proof of this colossal red shift.
"It is a possible explanation of the object's strange colours but one can come up with others, though all are relatively exotic," he said. "A red shift of 12.5 pushes far enough beyond the boundary of anything that we know today that I would have to have better proof before I could really be terribly confident about that."
Nevertheless, in a paper to be published in the Philosophical Transactions of the Royal Society, reported by PhysicsWeb, he concludes that it "remains an exciting possibility" that one of the first galaxies to have formed has just been glimpsed.
Alternative explanations include a distant quasar or galaxy with a particularly heavy shroud of dust; an unusually old galaxy filled with cool stars, which in itself implies star formation dates back further than presently believed; or even an exotic star, of a type not seen before, drifting through intergalactic space.
The matter may have to wait until 2008 when the Next Generation Space Telescope could get a better image of the object.