University of Hertfordshire scientist finds hidden stars

Professor Philip Lucas, of the University of Hertfordshire, led a team to researchers to detect dozens of rarely seen new-born stars, known as protostars.

They also discovered a new type of elderly giant nicknamed an 'old smoker', which can exist quietly for decades, before fading almost to invisibility and suddenly puffing out clouds of smoke.

The newly spotted stars are hidden in visible light by large amounts of dust and gas in the Milky Way, but infrared light allowed scientists to see them for the first time.

Professor Lucas made the ground-breaking discovery after surveying almost a billion stars in the night's sky over a decade-long period.

"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 ESO’s Very Large Telescope to get spectra of many of them individually.

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The research found stars never seen before in the Milky Way. (Image: PA Images/PA Wire)

"A spectrum shows us how much light we can see at a spread of different wavelengths, giving a much clearer idea of what we are looking at."

As well as 32 erupting protostars - some of which increased in brightness by more than 300-fold - the research discovered 21 red stars near the centre of the Milky Way.

These were a completely unexpected find and showed changes in brightness during the 10-year survey, puzzling Professor Lucas.

"We weren’t sure if these 21 stars were protostars starting an eruption, squalling new-borns if you will, or recovering from a dip in brightness caused by a disc or shell of dust in front of the star," he said.

"A third option was that they were older giant stars throwing off matter in the late stages of their life, puffing out gas like old smokers."

Analysis revealed they were actually a new type of red giant star, with Professor Dante Minniti, from Andres Bello University in Chile, saying: "These elderly stars sit quietly for years or decades and then puff out clouds of smoke in a totally unexpected way.

"They look very dim and red for several years, to the point that sometimes we can’t see them at all."

And Professor Lucas believes the discoveries could change what we know about space, continuing: "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 the Nuclear Disc and metal-rich regions of other galaxies."