A joint team from University of Arizona and University of Texas in the US has found that the sun periodically leaves Earth open to assaults from interstellar nasties in a way that most stars do not, the 'New Scientist' reported.
The sun protects humans from cosmic rays and dust from beyond the solar system by enveloping in the heliosphere -- a bubble of solar wind that extends past Pluto. These rays would damage the ozone layer and interstellar dust can dim sunlight and trigger an ice age.
However, when the solar system passes through very dense gas and dust clouds, the heliosphere can shrink until its edge is inside Earth's orbit. So, in their research, the team, led by David Smith, has calculated the squeezing of various stars' protective "astrospheres".
