All of these planets orbit stars. But a very few, if any, have been deemed potential candidates for life.
New work by an international team of astrobiologists suggests a few hundred thousand billion free-floating life-bearing Earth-size planets may exist in the space between stars in the Milky Way.
The research team is led by Professor Chandra Wickramasinghe, Director of the Buckingham Centre for Astrobiology at the University of Buckingham, UK. Their findings are published online in the Springer journal Astrophysics and Space Science.
The scientists have proposed that these life-bearing planets originated in the early universe within a few million years of the Big Bang.
In fact, the researchers note, these planets make up most of the so-called “missing mass” of galaxies.
The scientists calculate that such a planetary body would cross the inner solar system every 25 million years on the average. Furthermore, during each transit, zodiacal dust — including a component of the solar system’s living cells — becomes implanted at its surface.
Therefore, the team argues, the free-floating planets would then have the added property of mixing the products of local biological evolution on a galaxy-wide scale.
In their paper, Wickramasinghe and the team have increased this grand total of planets to a few hundred thousand billion — a few thousand for every Milky Way star — each one harboring the legacy of cosmic primordial life.
Free-floating planets in the Milky Way, they contend, outnumber stars by factors of thousands.
For more information, go to:
Wickramasinghe, N. C. et al. (2012), “Life-bearing primordial planets in the solar vicinity,” Astrophysics and Space Science.
By Leonard David