The alien solar system looks just like ours.
The discovery by Dr Roberto Sanchis-Ojeda and his team at the Massachusetts Institute of Technology is reported in Nature journal.
Transits of the planets were analysed over spots on the star Kepler-30 and it was found their orbital planes mirror those round our Sun.
So similar are the alignments that, they conclude, this very distant cousin of our solar system was formed the same way â€“ from a single spinning disc of gas and dust.
Their discovery was described as â€˜fascinatingâ€™ by Prof Drake Deming of the University of Maryland, who reviewed it in the journal.
He said: â€˜The researchers deduce all three transiting planets in this system orbit in the same plane, to within one angular degree of inclination. This very tight arrangement in Kepler-30 immediately brings to mind the closely aligned orbits of the solar system.â€™
The observation sheds light on the conditions that determine the architecture of a planetary system.
â€˜The fact some planetary orbits can be neatly aligned with the plane of their starâ€™s equator, whereas others are wildly misaligned, shows we have much still to learn about the formation and orbital evolution of planets,â€™ Prof Deming added.