By Dr David Whitehouse
BBC News Online science editor
Astronomers working in Chile think they may have taken the first direct image of a planet circling another star.
The small, red object tested the Yepun unit to its limits
The star, called 2M1207, is 230 light-years away and is very much smaller and fainter than our own Sun.
The pictured companion is 100 times fainter still and tested the technical limits of the Yepun telescope.
Astronomer Christophe Dumas said: "It is a strange feeling that it may indeed be the first planetary system beyond our own ever imaged."
Benjamin Zuckerman, of the University of California, in Los Angeles, added: "If the candidate companion of 2M1207 is really a planet, this would be the first time that a gravitationally bound exoplanet has been imaged around a star or brown dwarf."
And Anne-Marie Lagrange, from the Grenoble Observatory, France, said: "Our discovery represents a first step towards opening a new field in astrophysics: the imaging and spectroscopic study of planetary systems.
"Such studies will enable astronomers to characterise the physical structure and chemical composition of giant and, eventually, terrestrial-like planets."
At the limit
The observations were made with the 8.2m Yepun unit, part of the Very Large Telescope (VLT) facility operated by the European Southern Observatory (Eso) on Cerro Paranal in the Atacama Desert.
In April, a team of European and American astronomers used Yepun to detect a faint and very red point of light near the brown-dwarf star 2M1207.
The star has a mass of about a few per cent of our Sun's mass and is not able to sustain nuclear fusion reactions in its core to produce energy in the same way as our Sun does.
2M1207 is thought to be about eight million years old. The star is a member of the TW Hydrae stellar association.
The VLT has four 8.2m telescopes
Working at the limits of its ability, the Yepun telescope was able to obtain a spectrum of the faint red object seen alongside 2M1207.
The spectrum showed the signatures of water molecules and confirms that the object must be small and light.
The researchers are not completely certain the object is an associated planet but they believe that further observations will prove this.
These observations will take a year or so. In the meantime, the astronomers are referring to the object as a "giant planet candidate companion".
On several occasions during the past few years, astronomical images have revealed objects that appear to be exoplanets. After further study, however, none of these candidates has proved to be convincing.
During its TW Hydrae association survey, the Yepun telescope was operating in its adaptive optics mode. This flexes the mirror to compensate for the Earth's atmospheric turbulence - to produce a much sharper image.
"If these images had been obtained without adaptive optics, the object would not have been seen," said Gael Chauvin of Eso.
"The thrill of seeing this faint source of light in real-time on the instrument display was unbelievable," said Christophe Dumas, also of Eso.
A series of exposures was made through various optical filters.
The researchers say the spectrum obtained is probably that of a "young and hot planet" that will cool down to become a gas-giant world like Jupiter.
A detailed paper concerning the discovery has been submitted to the journal Astronomy and Astrophysics.