The search for Earth-like planets will take a leap forward tomorrow with the launch of a powerful new space telescope.
The Kepler telescope will offer the first chance of discovering whether habitable planets orbit distant stars.
Astronomers claim that if the 3.5 year mission is successful it will change humanity's view of the universe forever.
Some experts believe our galaxy, the Milky Way, could be teeming with Earth-like worlds, and the new telescope will help to investigate this.
NASA is due to blast the Kepler telescope into space from Cape Canaveral in Florida at around 3.45am Irish time tomorrow.
Carried on top of a Delta II rocket, it will be placed in an orbit trailing the Earth around the Sun.
The 5 metre telescope will keep its single eye fixed on a patch of sky equivalent to the size of a human hand held at arm's length.
At its heart is a 55-inch wide mirror and 95 megapixel camera which will measure the brightness of around 100,000 stars in the constellations Cygnus and Lyra every 30 minutes.
Target stars will vary in distance from tens of light years to around 3,000 light years.
Planets will be found by detecting almost imperceptible 'winks' - the dimming that occurs as they move across the face of their parent stars.
Whether or not a planet is suitable for life depends on how distant it is from its parent star.
A planet that occupies the so-called 'Goldilocks zone' - an orbital band where conditions are not too hot and not too cold, but 'just right' - could have liquid water on its surface in the form of oceans, seas, lakes and rivers.
Ground-based telescopes measure the way stars 'wobble' as they feel the tug of gravity from orbiting planets, but this technique cannot easily find Earth-sized planet orbiting stars at Earth-like distances.
The 'transit' method used by Kepler is much more suited to this task.
Once detected, the size of a planet's orbit can be established from the mass of the star and the length of time between each wink. The planet's size is calculated from the amount of dimming and the size of the star.
Scientists believe that even at a conservative estimate Kepler could discover around 500 Earth-like planets.
Astronomer Dr Alan Boss, a member of the Kepler team from the Carnegie Institute in Washington DC, believes there might be as many habitable Earth-like planets in the Milky Way as there are Sun-like stars - roughly 100 billion.
