``This is the first planet we have been able to verify is real,'' he said. The sighting by the human eye validates the existence of other planets that astronomers have located by deduction over the years, Marcy said. ``This lends credibility to all the other planets we have found, and which may harbour life,'' he said. ``It is very exciting. This ties directly to the possibility of life on other planets and the existence of planets for humans to colonise.'' Macy and a colleague, Paul Butler of the Department of Terrestrial Magnetismat the Carnegie Institution of Washington, D.C., led the team that made the discovery.

An official name has yet to be given to the planet, which is nearly 18 times the size of the Earth and has a surface temperature of about 3,500 degrees Fahrenheit. Marcy wants it to bear the name ``Silhouette'' or ``Shadow'' in tribute to the image captured by telescopes on Monday, November 7.

The planet revolves around a sun similar to the Earth's, but about five percent larger. The planet circles its sun in 3.5 Earth days, a voyage that the Earth makes around its sun in a year. The planet's orbit is 20 times closer to its sun than the earth is to its sun. There is almost certainly water on the planet, but it would be in the form of vapour because of the heat, Marcy said. ``We will be studying this thing like crazy for the next year,'' Marcy said. The shadow planet is 150 light years from the Earth, virtually next door in cosmic terms. The Milky Way galaxy is 100,000 light years across.

``For astronomers, this is notjust in your back yard, it is on your back porch,'' Marcy said. Marcy and his colleagues will scour the night sky to ascertain whether other planets revolve around the shadow planet's sun.

Marcy and Butler specialise in pinpointing stars that appear to wobble. The astronomers figured that star wobbling was the result of gravitational tugging by orbiting planets. ``For the first time in history, we have direct observation,'' Marcy said. ``We never saw a planet albeit a shadow until now.''