When galaxies collide, their stars are not actually destroyed. These turbulent dynamics actually trigger the formation of new generations of stars, and potentially even planets to accompany them.
[Related: Behold six galactic collisions, masterfully captured by Hubble.]
Astronomers using the Hubble Space Telescope took a closer look at 12 of these interacting galaxies. These galaxies all have long tails of gas, dust and a multitude of stars. Hubble can detect ultraviolet light and has discovered 425 clusters of newborn stars located along these galactic tails that resemble a necklace of lights or pearls. Each of these clusters contains up to a million newborn blue stars. The results were described in a study published in the Monthly Notices of the Royal Astronomical Society in September 2023. A new image of the pearl necklace galaxy (Galaxy AM 1054-325) was released by NASA February 8.
Galactic collisions and high pressure
When galaxies interact with each other, gravitational tidal forces extract long streams of gas and dust from the materials that make up each galaxy. THE Antennas And Mouse galaxies have long, narrow finger-like tendrils and are common examples of what these galactic tails look like.
“As galaxies merge, clouds of gas collide and collapse, creating a high-pressure environment in which stars could form,” said Jane Charlton, co-author of the study and astronomer at Penn State University. said in a statement. “The interiors of these mergers have been well studied, but less is known about possible star formation in the debris resulting from these mergers, such as in tidal tails.”
Cocks of young stars
In their study, a team of scientists used new observations and archival data to estimate the age and mass of tidal tail star clusters. Only 10 million years old, these clusters are very young and appear to form at the same rate along tails that extend thousands of light years.
“It’s a surprise to see so many young objects in the queues. This tells us a lot about the efficiency of cluster formation,” Michael Rodruck, study co-author and astronomer at Randolph-Macon College. said in a statement. “With tidal tails, you will build new generations of stars that otherwise might not have existed.”
The tails appear to take the spiral arm of a galaxy and stretch it further out into space. The outer arm is pulled in a gravitational tug of war between the two interacting galaxies.
Galaxies as a time capsule
Even before these galactic mergers occurred, galaxies were rich in dusty clouds of molecular hydrogen. These clouds may have just been unable to move, but eventually they jostled and started colliding. This activity then compressed the hydrogen to such an extent that it created a massive star birth storm.
[Related: How do you make cosmic sausage?]
Scientists still don't know exactly what the fate of these star clusters will be. They could remain gravitationally intact and eventually transform into globular star clusters. It is possible that they will also disperse to form a halo of stars around their host galaxy, or even be rejected and become wandering intergalactic stars.
Nearby galaxies observed by Hubble like these can be used as an indicator of what happened in our universe millions of years ago and provide a way to peer into the distant past.
“We think star clusters in tidal tails may have been more common in the early universe.” Charlton said.“When the universe was smaller and galaxy collisions more frequent.”