Scientists Drastically Underestimate the Number of Planets in the Milky Way

The presumption in the scientific community has been that planet’s are like rare little gems, serendipitous collections of mass around those stars lucky enough to have them. Our solar system was unusually lucky, housing eight (or nine if you grew up prior to 2000) of these fantastic solar satellites. Recent evidence, however, seems to point to planets being a much more ubiquitous occurrence in the universe than previously thought. In fact, on average every sun has at least one planet, unveiling a Milky Way galaxy that is home to somewhere in the neighborhood of a trillion planets.

These new findings are from a six-year survey of millions of stars. Each star was investigated using a network of professional and amateur astronomers using telescopes in our southern hemisphere. They locate the planets using a detection method called gravitational microlensing. Planets are not necessarily visible, even to today’s powerful telescopes. However, the light of their host stars are, and the impact of gravitational fields on that light is very telling. A star’s solar output is amplified by the star’s own gravitational field. The distorted array of that light is evidence of the star’s own gravitational field, but if there are extrasolar planets orbiting that star, their gravitational fields will further widen that lens. Researchers examined 100 million stars every night during the lifespan of the study, and noted those with promising light-curve amplifications. Between 2002 and 2007, Popular Science notes, 500 stars were found to have these kinds of light amplifications and in ten such stars it was possible to actually see the planet’s gravitational effect on the star’s output. Statistically, one in six had a planet with Jupiter-like mass, three had Neptune-like planets, and two-thirds had a super earth, or large rocky planets.

Senior astronomer at the SETI Institute, Seth Shostak used the following simile to illustrate just how proliferous planets actually are: “Planets are like bunnies; you don’t just get one, you get a bunch, so really, the number of planets in the Milky Way is probably like five or 10 times the number of stars. That’s something like a trillion planets.” The sheer number of planets within our galaxy, although not a guarantee that many will be habitable by human colonists, nonetheless place the odds in our favor. “It’s not unreasonable at this point to say there are literally billions of habitable worlds in our galaxy,” Shestak says. However, other astronomers are not so sure, according to Popular Science, saying that increasing the number of planets does not necessarily increase the odds that those planets are habitable.