Astronomers have discovered a new type of red giant star near the centre of the galaxy.
A project led by the University of Hertfordshire has spent 10 years studying almost a billion stars in the Milky Way.
The scientists have now found hidden stars, including a new type of elderly giant star nicknamed "an old smoker".
The team said the stars looked dim for several years before they puffed out huge clouds of smoke into space.
Prof Philip Lucas of the University of Hertfordshire, who led the operation, said his global team also detected dozens of rarely seen newborn stars, known as protostars.
Most of these stars were hidden from view in visible light by large amounts of dust and gas in the Milky Way.
However the scientists used infrared light, which allowed the stars to be seen for the first time.
Mr Lucas said: "About two thirds of the stars were easy to classify as well-understood events of various types.
"The rest were a bit more difficult, so we used the European Southern Observatory's Very Large Telescope to get spectra of many of them individually."
Astronomers from the UK, Chile, South Korea, Brazil, Germany and Italy worked with Mr Lucas on the research. The team was helped by a British-built infrared telescope based in the Chilean Andes.
Mr Lucas said the discoveries could change what we know about the way elements were distributed across space.
He added: "Matter ejected from old stars plays a key role in the life cycle of the elements, helping to form the next generation of stars and planets.
"This was thought to occur mainly in a well-studied type of star called a Mira variable.
"However, the discovery of a new type of star that throws off matter could have wider significance for the spread of heavy elements in other galaxies."