If the alignment is especially perfect, any big planets attending the nearer star will get into the act, adding their own little bumps to the more distant starlight.

That is exactly what started happening on March 28, 2006, when a star 5,000 light years away in the constellation Scorpius began to pass in front of one 21,000 light years more distant, causing it to flash. It was picked up by the Optical Gravitational Lensing Experiment, or Ogle, a worldwide collaboration of observers who keep watch for such events.

Ogle in turn immediately issued a worldwide call for continuous observations of what is now officially known as OGLE-2006-BLG-109L. The next 10 days, as Andrew Gould of Ohio State said, were “extremely frenetic.”

Among those who provided crucial data and appeared as lead authors of the paper in Science were a pair of amateur astronomers from Auckland, New Zealand, Jennie McCormick and Grant Christie, both members of a group called the Microlensing Follow-Up Network, or MicroFUN. Ms. McCormick, who described herself as “an ordinary New Zealand mother,” said she had done her observing with a 10-inch Meade telescope from a shed in her back yard.

Somewhat to the experimenters’ surprise, by clever manipulation they were able to dig out of the data not just the masses of the interloper star and its two planets but also rough approximations of their orbits, confirming the similarity to our own system. David Bennett of Notre Dame, said, “This event has taught us that we were able to learn more about these planets than we thought possible.”

As a result, microlensing is poised to become a major new tool in the planet hunter’s arsenal, “a new flavor of the month,” in the words of Dr. Seager. The new system, she said, is just the tip of the iceberg and the odds are that a lot of the ones that will be discovered could be like ours.

Only six planets, including the new ones, have been discovered by microlensing so far and the Scorpius event was the first in which the alignment of the stars was perfect enough for astronomers to detect more than one planet at once. Their success at doing just that on their first try bodes well for the future, astronomers say.

Alan Boss, a theorist at the Carnegie Institution of Washinton, said: “The fact that these are hard to detect by microlensing means there must be a good number of them  solar system analogues are not rare.”