Sara Seager, a planetary theorist at the Massachusetts Institute of Technology, said astronomers hunt for planets by detecting telltale wobbles they induce in their host stars, a method that selectively nets the too big or too near. Nevertheless, she said, “the fact is, as soon as astronomers started looking for low-mass planets, they found a whole bunch, and that’s a real breakthrough.” Just imagine the orgy of moderation that a more inclusive scan would reveal.

To some theorists, the new results virtually guarantee the existence of other Earthlike worlds.

“Suppose you have a tribe, and the most noticeable members are the warriors, because they’re adventuresome, they roam around, they’re the first to be spotted,” said Douglas N. C. Lin, a professor of astronomy and astrophysics at the University of California, Santa Cruz. “But you know that for every warrior, there’s a family behind the warrior.”

Dr. Lin continued, “Just as you can extrapolate from the warriors you see what the size of the larger population deep in the woods may be, so the presence of these short-period, super Earths implies that there are clusters of other planets farther out.” Potentially pleasant planets at that. “I would imagine that a significant fraction of ordinary Sunlike stars, maybe more than 10 percent, have habitable planets around them,” Dr. Lin said.

Whether habitable or abominable, planets are inescapable. “You make a star, you’re probably going to get planets,” said Seth Shostak, a senior scientist at the SETI Institute in Mountain View, Calif. “They’re like those knives that get thrown in for free when you order a Veg-o-matic.”

When a cloud of dust and gas collapses to make a new star, spinning faster and faster as it shrinks, competing forces of gravity, pressure and rotation cause some of its midriff to flatten into a disk, rather as the skirt of a skater flies into a circle as she pulls in her arms for a twirl. The planets in turn condense from the dust, gas and ice of that central disk, in sequences that researchers have just begun to model. In Dr. Lin’s view, planetary evolution is a kind of Darwinian affair, as embryonic planets compete to enlarge themselves with heavy metal “food” from the disk, while struggling not to be consumed by a sibling or pulled into the mother star.