London, Dec 2 : A new study has suggested that by looking at the cosmic microwave background (CMB), which is the first radiation emitted in the universe after the big bang, will help scientists find the birthplace of comets.
Comets that take longer than 200 years to orbit the Sun come from all directions in the sky.
That has long led scientists to believe that they were nudged out of a bubble-like halo of icy objects that surrounds the solar system - the Oort Cloud.
The objects probably formed from the same disc of material that gave rise to the planets, but were scattered outwards by Jupiter and Saturn a few hundred million years after their birth.
The Oort Cloud is too dim to be seen by telescopes, but astronomers believe it has two components.
Based on observations of long-period comets, an outer portion seems to extend from 20,000 to 200,000 astronomical units from the Sun.
Solar system models also predict the existence of an inner shell that stretches some 3000 to 20,000 AU from the Sun.
But, there is less evidence for this shell. Most passing stars are too distant to jostle the inner halo and dislodge comets.
Only a few recently spotted objects, such as the icy bodies 2006 SQ372 and Sedna, point to its existence.
Now, according to a report in New Scientist, a new study suggests that the inner Oort Cloud might be detectable by looking at all-sky surveys of the cosmic microwave background - the first radiation emitted in the universe after the big bang.
The inner Oort Cloud objects are dense enough at their orbital distance to block a significant portion of the cosmic radiation, and since the icy debris is roughly -268 degrees Celsius, about twice as warm as the CMB, it should show up in maps of the radiation.
The inner cloud would not be detectable if it formed a perfect sphere, since that would leave the same imprint on the CMB in all directions.
However, if a star passed close enough to the Sun to rearrange objects in the inner cloud, the distortions might be visible in the CMB, according to Daniel Babich and Avi Loeb of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
"A star that passes there would actually kick the cloud," said Loeb. "In principle, that would leave a signature that is detectable on the CMB," he added.
Maps made with the European Space Agency's Planck telescope, set to launch in April 2009, might reveal the signal, which could be used to determine the inner Oort Cloud's distance, shape and the distribution of its icy bodies.