Interstellar civilizations may thrive in globular clusters

KISSIMMEE, FLORIDA—If you want your civilization to reach the stars, you need to live somewhere special: tranquil enough for your culture not to be wiped out by some cosmic catastrophe, yet close enough to other stars to make interstellar travel possible. A pair of astronomers say they may have found the perfect place: deep inside a globular cluster. These densely-packed clutches of many thousands or millions of stars—of which there are around 150 in our Milky Way galaxy, like the cluster UKS1 above—were previously thought to be one of the worst places to look for an advanced civilization. First, because stars are so closely packed together they can potentially disrupt the orbits of planets around neighboring stars, and also because their stars are seriously old, forming before the universe was seeded with the heavier elements needed to make planets and life. But here today at a meeting of the American Astronomical Society, the team told attendees that we shouldn’t discount globular clusters so quickly. Of the thousands of exoplanets discovered by NASA’s Kepler mission, many are around stars with less heavy elements than the sun. Globular clusters are also typically made of small red slow-burning stars, all the hot and bright ones having long burned out. Such small stars give a civilization many billions of years of unchanging illumination so it can develop, and star’s size means its habitable zone is close in, where planets are less prone to disruption by neighboring stars. And having near-by neighbors means that any message takes months to travel between stars rather than years. So, when the Search for Extraterrestrial Intelligence (SETI) is deciding where to point their telescopes, they say, now they know where to look.