Lots Of Them
Scientists often see farther by standing on the shoulders of their tallest colleagues , but the latest extension of astronomical insight comes from an arid but remarkably un-dusty mountaintop in Chile called La Silla ,which hosts what can only described as a telescope theme park, sporting glass giants that are outliers of the world's great observatories
In recent years, a Swiss group headed by Michel Mayor of the University Of Geneva has used the 3.6 meter instrument of The European Organisation for Astronomical Research in the Southern Hemisphere to gather light for 'HARPS.' The High Accuracy Radial Velocity Planet Searcher detects the small wobbles in star motion that signal orbiting planets
At a conference in Nantes ,France, the group has announced finding a triple system of super-Earths - planets intermediate in mass between ours and Neptune- orbiting the star HD 40307.
Looking at HARPS scans to date , they count a total of 45 such objects with orbital periods shorter than 50 days, implying s that one sun-like star star out of three harbors such planets.
"Does every single star harbor planets and, if yes, how many?" wonders Mayor "We may not yet know the answer but we are making huge progress towards it."
Since the discovery of a planet around the star 51 Pegasi in 1995, more than 270 exoplanets have been found, the majority around solar-like stars. Most are hot , Jupiter sized giants of a sort current statistics suggest can be found orbiting 1 out of 14 stars. "With the advent of much more precise instruments such as the HARPS spectrograph on ESO's 3.6-m telescope at La Silla, we can now discover smaller planets, with masses between 2 and 10 times the Earth's mass," says Stéphane Udry,adding that "“Detection of planets with masses of about 2 Earth-masses --maybe less-- is possible,”
To do much better, astronomers will have to look through the next generation of NASA deep space telescopes- the first of which, the Webb Telescope, should be orbited within a decade.
There is a double irony in where the Swiss group announced its confirmation of the once-heretical doctrine of the Plurality Of Worlds. At Nantes in 1598 was declared the Edict granting freedom of religion to the French Protestant followers of John Calvin of Geneva. Two years later, putting too much faith in freedom of conscience , Giordano Bruno foolishly voiced the belief that ours might not be the only world riven by wars of religion, and was burnt at the stake for his trouble.This had a chilling effect on further speculation, despite the rapid advance of astronomical instruments in the decades that followed.
in 1624, Gallileo died under house arrest , his persecution by The Inquisition preceding by several decades the excommunication from his synagogue of Dutch lens grinder, Benedictus Spinoza, purveyor of telescope objectives to Christian Huygens and the Royal Society and author of the explicit phrase ' the plurality of worlds.' Thirteen years after he died in poverty,the Edict Of Nantes was revoked, and St Augustine's condemnation of scientific curiousity was restored to the reverence it still enjoys in some quarters to this day.