Galaxy colliding, stars waking up: Hubble's astonishing discovery

A long trail of clustered stars follows galaxy interactions

When galaxies collide at night, they cook up new generations of stars that might never have been born. These close encounters between galaxies cause a gravitational tug of war, and gas and dust are pulled into large streams. the Hubble Space TelescopeTheir vision is so sharp that they can see clusters of newborn stars suspended along these tidal tails. They form when clusters of gas collapse under gravity to form about a million newborn stars in each cluster. These “string of pearls” features were likely more common in the early universe when galaxies collided frequently.

Galaxy AM 1054-325 has been distorted into an S shape from a regular, pancake-like spiral due to the gravitational pull of a nearby galaxy, as seen in this image taken by the Hubble Space Telescope. As a result, clusters of newborn stars form along a tidal tail extending thousands of light-years, resembling a string of pearls. They form when clusters of gas collapse under gravity to form about a million newborn stars in each cluster. Image source: NASA, ESA, STScI, Jayanne English (University of Manitoba)

The Hubble Space Telescope tracks “string of pearls” star clusters in galactic collisions

Contrary to what you might think, galactic collisions do not destroy stars. In fact, the fluctuating dynamics trigger new generations of stars, and potentially their accompanying planets.

now NASAThe Hubble Space Telescope focused on 12 interacting galaxies that have long, tadpole-like tidal tails made up of gas, dust, and a large number of stars. Hubble's remarkable resolution and ultraviolet sensitivity have revealed 425 clusters of newborn stars along these tails, which look like strings of holiday lights. Each cluster contains up to a million blue newborn stars.

Detecting new star clusters

Populations in the tidal tails have been known for decades. When galaxies interact, gravitational tidal forces pull in long streams of gas and dust. Two common examples are the antennae and mice with their long, narrow, finger-like projections.

A team of astronomers used a combination of new observations and archival data to obtain the ages and masses of tidal star clusters. They found that these clusters are very young, only 10 million years old. They appear to form at the same rate along tails extending thousands of light-years.

The future of tidal tail star clusters

“It's a surprise to see so many small things in the tails. It tells us a lot about the efficiency of mass formation,” said lead author Michael Rudrack of Randolph-Macon College in Ashland, Virginia. “Using tidal tails, you will build new generations of stars that were not It would not exist otherwise.”

The tails appear to take the galactic spiral arm and extend it out into space. The outer part of the arm is pulled like candy from a gravitational tug of war between a pair of interacting galaxies.

Before the mergers, galaxies were rich in dust clouds of molecular hydrogen, which may have remained inert. But the clouds crowded together and collided with each other during the encounters. This compressed the hydrogen to the point that it triggered a firestorm of star birth.

The fate of these suspended star clusters is uncertain. They may remain gravitationally intact and evolve into spherical star clusters – such as those orbiting outside the plane of our planet. milky way galaxy. Or they may scatter to form a halo of stars around their host galaxy, or be jettisoned to become intergalactic wandering stars.

String-of-pearl star formation may have been more common in the early universe when galaxies frequently collided with each other. These nearby galaxies observed by Hubble are a proxy for what happened a long time ago, and are therefore laboratories for looking into the distant past.

Reference: “Star Clusters in Tidal Debris” by Michael Rudrak, Jane Charlton, Sanchaita Borthakur, Aparna Chhetri, Patrick R. Dorrell, Debra Elmegren, Jayne English, Sarah C. Gallagher, Karel Gronwall, Karen Knerman, Iraklis Konstantopoulos, Yuexing Li, Mopia Maggie Brendan Mullan, Gillies Trenshaw and William Vacca, September 29, 2023, Monthly Notices of the Royal Astronomical Society.
doi: 10.1093/manras/stad2886

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, operates the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts science operations on Hubble and Webb. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, DC