The Hubble Space Telescope has made an astonishing discovery, revealing the presence of shining diamonds in the form of star clusters within interacting galaxies. Scientists have compared this phenomenon to cosmic “strings of pearls,” as these clusters are found in the long “tails” formed when spiral galaxies interact.
When two spiral galaxies come close to each other, their gravitational forces cause their spiral arms to unravel and form tidal tails that can stretch for thousands of light-years. These tidal tails become intense regions of star formation due to the gas and dust present in the spiral arms. The stirring up of this gas and dust ignites a firestorm of star formation, resulting in the creation of young star clusters.
A team of astronomers, led by Michael Rodruck of Randolph-Macon College in Virginia, used Hubble images to study 12 interacting galaxies across seven different systems. They identified 425 massive star clusters within the tidal tails of these galaxies. Each cluster contains approximately a million young, blue stars that emit significant amounts of ultraviolet light.
To determine the age of these star clusters, the team consulted archival ultraviolet observations from NASA’s Galaxy Evolution Explorer and the Swift mission. They found that the clusters still contained gas, evidenced by strong emission lines in their spectra. This indicated that the clusters must be younger than 10 million years, as negative feedback from young stars would have blown the gas out of the cluster by that time.
“It’s a surprise to see lots of the young objects in the tails,” said Rodruck. “It tells us a lot about cluster formation efficiency. With tidal tails, you will build up new generations of stars that otherwise might not have existed.”
These star clusters within tidal tails are significantly more massive than young star clusters found in our own galaxy. They resemble ancient and compact globular clusters found in the Milky Way’s halo. This raises intriguing questions about whether Hubble is witnessing events similar to how globular clusters formed long ago or if these modern clusters will eventually disperse.
The findings of this study were published in the Monthly Notices of the Royal Astronomical Society last year. This discovery sheds light on the fascinating processes of star formation and cluster formation within interacting galaxies. The Hubble Space Telescope continues to provide us with awe-inspiring images and valuable insights into the mysteries of our universe.
