An international team of astronomers has discovered 96 star clusters hidden by dust in the Milky Way galaxy.
The new clusters were identified using data from the VISTA infrared survey telescope, which operates under the auspices of the European Southern Observatory (ESO) in Chile.
”This discovery highlights the potential of VISTA for finding star clusters, especially those hiding in dusty star-forming regions in the Milky Way’s disc,” said Jura Borissova, lead author of the star cluster study which will appear in the journal Astronomy & Astrophysics.
According to Dante Minniti, lead scientist of the Via Lactea program (VVV), the majority of stars with more than half of the mass of our Sun form in groups known as open clusters. These clusters are the building blocks of galaxies and vital for the formation and evolution of galaxies such as our own.
However, stellar clusters form in very dusty regions that diffuse and absorb most of the visible light emitted by young stars – making them invisible to most sky surveys, but not to the 4.1-m infrared VISTA telescope.
“In order to trace the youngest star cluster formation we concentrated our search towards known star-forming areas. In regions that looked empty in previous visible-light surveys, the sensitive VISTA infrared detectors uncovered many new objects,” he explained.
Indeed, by using carefully tuned computer software, the team was able to remove the foreground stars appearing in front of each cluster in order to count the genuine cluster members. Afterwards, scientists conducted visual inspections of the images to measure cluster sizes, distance, age and the effects of interstellar dust.
“We found most of the clusters are very small and only have about 10-20 stars,” said Radostin Kurtev, another member of the team.
“Compared to typical open clusters, these are very faint and compact objects – the dust in front of these clusters makes them appear 10,000 to 100 million times fainter in visible light. It’s no wonder they were hidden.”
Since antiquity, only 2,500 open clusters have been found in the Milky Way, but astronomers estimate there might be as many as 30,000 still hiding behind the dust and gas. While bright and large open clusters are easily spotted, this is the first time that so many faint and small clusters have been positively identified at once.
Of course, the new 96 open clusters is likely only the tip of the iceberg for additional discoveries.
“We’ve just started to use more sophisticated automatic software to search for less concentrated and older clusters. I am confident that many more are coming soon,” added Borissova.