Astronomers have discovered a mysterious group of giant old stars at the center of the Milky Way that are releasing clouds of dust and gas the size of our solar system. These stars, named "Smoking Guns," sleep quietly for many years, disappear almost without a trace, and then suddenly emit huge clouds of smoke. The discovery was made while monitoring infrared light from nearly a billion stars during a 10-year survey of the night sky.
Professor Philip Lucas from the University of Hertfordshire said: "They are ejecting material suddenly. This is a new type of star and they all appear to be clustered in the same area of the sky, very close to the center of the Milky Way."
Astronomers aimed to capture rare newborn stars - called protostars - going through a period equivalent to the peak of stellar growth. During this time, the young star rapidly gains mass by gobbling up surrounding star-forming gas, causing a sudden increase in luminosity.
The research team tracked hundreds of millions of stars and found 32 exploding protostars whose brightness increased by at least 40 times, and some even increased by more than 300 times.
However, another group of red giant stars near the center of the Milky Way unexpectedly appeared in the analysis. Researchers used the European Southern Observatory's Very Large Telescope to study these stars in more detail. Seven of the stars are believed to be a new type of red giant, which the researchers named "Smoking Gun." Lucas believes that convection and instabilities within the star could trigger the release of huge plumes of smoke.
"These clouds are the size of the solar system," Lucas said. "We hypothesize that these are dust ejected in one direction, possibly from a region on the star's surface."
The findings have broader implications because material released into interstellar space from dying stars seeds the next generation of stars.