Hubble detects celestial 'string of pearls' star clusters in intergalactic collisions

When spectacular cosmic events such as interstellar collisions occur, it sets off a reaction to the formation of new stars, and new planets that would not have formed otherwise. The gravitational force that drives the collisions between these galaxies creates tails – long thin strips of stars and interstellar gas.

The Hubble Space Telescope's field of vision is so sharp that clusters of newborn stars can be seen in these tidal tails. They form under the gravitational pull of gas knots to form about 1 million newborn stars per cluster.

In particular, NASA's Hubble Space Telescope is home to 12 interacting galaxies with long, tadpole-like tidal tails of gas, dust, and abundant stars. Hubble's exquisite sharpness and sensitivity to ultraviolet light have detected 425 clusters of newborn stars in these tails that look like strings of holiday lights.

Each cluster contains 1 million blue, newborn stars.

Clusters in wave tails have been known for decades. When galaxies interact, gravitational forces pull out long streamers of gas and dust. Two famous examples are the Antennae and Maize galaxies with their long, narrow, finger-like projections.

In a recently published study Monthly Notices of the Royal Astronomical Society Astronomers used the infrared capabilities of NASA's Hubble Space Telescope to study the tidal tail clusters and study their ages and masses, along with the properties of the merging galaxies.

Michael Rodruck of Randolph-Macon College is lead author of the study, along with co-authors including Arizona State University scientists Sanjayeda Porthakur and Karen Kinnerman of the School of Earth and Space Exploration.

A team of astronomers used a combination of new observations and archival data to derive the ages and masses of tidal comet clusters. They found that these clumps are very young – 10 million years old. And they form at the same rate in tails that stretch for thousands of light-years.

“These observations tell us how stars form and what regulates those processes. This knowledge is critical to understanding how stars form in our own galaxy,” said Associate Professor Sanjaeeta Porthakur, an observational astronomer specializing in extragalactic astronomy in ASU's School of Earth Sciences. and space exploration.

Tails are like taking the spiral arm of a galaxy and stretching it out into space. The outer part of the arm is pulled from the gravitational pull between a pair of interacting galaxies.

Before the merger, the galaxies were filled with dusty clouds that may have simply been dormant. But during the meetings the clouds rumbled and collided with each other. This compressed the hydrogen, fueling the firestorm of star birth.

The fate of these constellations is uncertain. They can remain gravitationally intact and evolve into globular clusters, such as orbiting outside the plane of our Milky Way Galaxy. Or they may disperse to form a halo of stars around their host galaxy or become wandering intergalactic stars.

“It is very exciting to use Hubble's data from different periods and data from other telescopes to provide the culmination of more than two decades of work on star clusters in tidal tails,” said assistant author Professor Karen Kinierman. “I started working on this project as an undergraduate at Penn State in 1999, and the same data and results are used here. When I came to ASU in 2007 (principal investigator) we got more data from the Hubble project. .”

This string-of-pearl star formation may have been more common in the early universe, when galaxies collided more frequently. These nearby galaxies observed by Hubble are a proxy for what happened a long time ago, and therefore allow us to see into the distant past.

“It's surprising to see so many young objects in the tails. It tells us a lot about the clustering ability,” Rodruck said. “With tidal tails, you create a new generation of stars that otherwise wouldn't have existed.”