While 1,900 planets have been discovered outside our solar system, these are the first to be seen that are still forming.
The discovery, reported in the journal Nature, has provided scientists with direct evidence of how gas and dust particles coalesce to create planets.
"We have found a clear case where we can join all of the dots showing how planets are forming by accreting the gas and dust left over from the formation of their star," said one of the study's authors, Professor Peter Tuthill of the University of Sydney.
The team of astronomers made the discovery while examining a distant star called Lick-Calcium 15 (LkCa 15), which is located about 450 light-years away in the constellation of Taurus.
The young star is only two million years old and is still surrounded by the circumstellar disk of gas and dust from which it formed.
Over a period of five years the astronomers focused on a large gap in the circumstellar disk that was being cleared out by the newly forming planets as they swept up material that would have otherwise fallen onto the star.
The astronomers identified light emissions caused by very hot gas falling onto the newly forming planet which they named LkCa 15 b.