from NASA Hubble space telescope has revealed a celestial phenomenon that illustrates the impressive consequences of galaxy collisions. Through his keen and sensitive vision, Hubble has tracked a “string of pearls” cluster of newborn stars along tidal tails formed from the interactions of 12 galaxies.
This discovery sheds light on the dynamic processes that give rise to new generations of stars during such cosmic encounters.
When galaxies collide
Galaxy collisions are vast, slow-moving events that occur over millions to billions of years, where two or more galaxies interact gravitationally with each other. Despite the dramatic name, these collisions are not as chaotic as one might expect due to the enormous distances between stars within galaxies.
It is rare for stars within colliding galaxies to actually collide. Instead, gravitational forces significantly alter the shapes and structures of galaxies.
While it may seem like galaxy collisions would destroy stars, the reality is that these encounters trigger explosive star formation. The collisions catalyze the birth of new stars and, presumably, the planets that accompany them.
“String of Pearls” Star Clusters
The gravitational tug-of-war between interacting galaxies draws up gas and dust in long streams, setting the stage for the creation of star clusters. These clusters, each containing up to a million newborn blue stars, are strung along the tails like luminous beads, forming a spectacular “string of pearls.”
The Hubble Space Telescope, which is particularly sensitive to ultraviolet light, has been instrumental in discovering 425 of these star clusters. The interactions stretch the galaxies’ material into long, tadpole-like tails that look like strings of Christmas lights.
A firestorm of star birth
These phenomena, although they have been known for decades through examples such as the Antennae and Mouse galaxies, have never been observed with such clarity and detail.
Before their encounters, the galaxies were rich in clouds of molecular hydrogen dust that, without the violent interactions, might have remained dormant. However, collisions push these clouds, compressing the hydrogen and causing a storm of star birth.
Very young star clusters
A team of astronomers, led by Michael Rodruck of Randolph-Macon University in Ashland, Virginia, analyzed a combination of new observations and archival data to determine the ages and masses of these tidal tail star clusters.
Surprisingly, the clusters are very young, only about 10 million years old, and appear to form at a constant rate along tails that stretch for thousands of light years.
“It is a surprise to see many young objects in the queues. It tells us a lot about the efficiency of cumulus formation,” Rodruck said. “With tidal tails, new generations of stars will be built that otherwise would not have existed.”
Processes that shaped the universe.
However, the future of these star clusters remains uncertain. They could evolve into globular star clusters, similar to those orbiting the Milky Way, disperse to form a stellar halo around their host galaxy, or even become wandering stars thrown into the intergalactic medium.
This observation not only provides information about the mechanisms of star formation, but also serves as a window to the past. In the early universe, when galaxy collisions were more common, this “string of pearls” star formation may have played a crucial role in the cosmic landscape. The galaxies observed by Hubble act as surrogates for these ancient events, offering a unique opportunity to study the processes that shaped the universe.
More about galaxy collisions
When galaxies collide, their gas and dust can be compressed, causing bursts of star formation that illuminate the merging galaxies. This process can lead to the creation of stellar nurseries, where new stars are born at an accelerated rate compared to the more constant rate observed in solitary galaxies.
Over time, the gravitational attraction between galaxies entangles them, forming a new galaxy, often larger and irregular in shape. The Milky Way itself is on a collision course with the Andromeda galaxy, an event that is predicted to occur in about 4 billion years.
These cosmic encounters are not only visually impressive but also scientifically invaluable, offering insights into the evolution of galaxies, the distribution of dark matter, and the cosmic web that structures the universe. The resulting galaxies can be elliptical, spiral or irregular in shape, depending on the mass and composition of the colliding galaxies and the dynamics of their interaction.
Through the study of galaxy collisions, astronomers can better understand the life cycle of galaxies, from their formation to their eventual merger, shedding light on the future of our own galaxy within the ever-expanding universe.
Image credit: NASA, ESA, STScI, Jayanne English (University of Manitoba)
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