PARIS: Nearing the end of their life, they sit quietly for long periods of time, barely noticeable, before suddenly puffing out a cloud of smoke.

A ‘mysterious new type’ of star, nicknamed old smoker, has been discovered hiding in the heart of our Milky Way galaxy, astronomers revealed on Friday.

The “peculiar” puffing behaviour of these stars has never been seen before in such red giants, according to astrophysicist Philip Lucas.

The international team of scientists behind the discovery had not been looking for such old stars during their 10-year survey, which took in hundreds of millions of stars across the sky.

Instead they were using the VISTA telescope in the Chilean Andes to search for newborn stars — called proto-stars — which are prone to frequent, exuberant eruptions.

They spotted 32 proto-stars, “the largest number anyone has ever found before in one batch”, said Lucas, a professor at the UK’s University of Hertfordshire and lead author of a new study.

But lingering in the background was a “nice surprise”, he added.

‘We don’t fully understand

The old smokers were puffing right in the centre of the Milky Way, a densely packed and metal-rich region called the Nuclear Stellar Disc.

“What was surprising about this new discovery is that we’re seeing stars that were just sitting doing nothing at all,” Lucas said.

Then abruptly the stars would become between 40 and 100 times dimmer, sometimes so faint that the telescope’s infrared vision could barely spot them.

A couple of years later, seemingly without warning, they would return to their former brightness.

Published in Dawn, January 27th, 2024