Behold six galactic collisions, masterfully captured by Hubble

The mergers can teach us about how stars are born.

By Jessica Boddy

Published

Interacting galaxies seen among stars through a telescope
This image, taken with the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS), both installed on the NASA/ESA Hubble Space Telescope, shows the peculiar galaxy NGC 3256. ESA/Hubble, NASA

To ring in the new year, NASA and the European Space Agency (ESA) dropped six captivating images of galaxies smashing into one another. The vistas were taken by the Hubble Space Telescope as part of the recent HiPEEC (Hubble imaging Probe of Extreme Environments and Clusters) survey, a project that aims to study how fast stars can form in systems like these.

Mergers like the ones depicted aren’t very common, and they’re quite valuable for learning more about how stars are born. “These systems are excellent laboratories to trace the formation of star clusters under extreme physical conditions,” ESA said in a statement.

When these rare collisions happen, shockingly dense and bright patches of stars crop up—you can see those bright spots in this collection of images, almost as if they’re glimmering badges of honor born from violent mergers. For comparison, here in the Milky Way, these bright patches known as star clusters pop up with masses that are 10 thousand times that of our Sun. But in these energy-packed galactic collisions, the clusters can clock in at millions of times the mass of our Sun.

And those super luminous clusters stick around. As the ESA puts it, “even after the collision, when the resulting galactic system begins to fade into a more quiescent phase, these very massive star clusters will shine throughout their host galaxy, as long-lasting witnesses of past merging events.”

By observing these clusters with ultraviolet and near-infrared cameras, Hubble scientists can discern their ages and masses, which helps them understand how quickly or slowly stars form there. It’s just one piece of the puzzle when it comes to understanding how star systems are born as a whole.

You can check out all of the collisions below, and older images of colliding galaxies captured by Hubble here.

The galaxy system NGC 1614 has a bright optical centre and two clear inner spiral arms that are fairly symmetrical. It also has a spectacular outer structure that consists principally of a large one-sided curved extension of one of these arms to the lower right, and a long, almost straight tail that emerges from the nucleus and crosses the extended arm to the upper right. The galaxy appears to be the result of a tidal interaction and the resulting merger of two predecessor systems. The system has a nuclear region of quasar-like luminosity, but shows no direct evidence for an active nucleus. It is heavily and unevenly reddened across its nucleus, while infrared imaging also shows a "ridge" of dust. The linear "tail" to the upper right and extended arms to the lower right are likely the remains of an interacting companion and the tidal plume(s) caused by the collision. NGC 1614 is located about 200 million light-years away from Earth in the constellation of Eridanus, the River.
Located 200 million light-years from earth, the galaxy system NGC 1614 has an extra bright center. It can be found in the constellation of Eridanus, known as the River. NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
The galaxy pictured in this Hubble Picture of the Week has an especially evocative name: the Medusa merger.  Often referred to by its somewhat drier New General Catalogue designation of NGC 4194, this was not always one entity, but two. An early galaxy consumed a smaller gas-rich system, throwing out streams of stars and dust out into space. These streams, seen rising from the top of the merger galaxy, resembles the writhing snakes that Medusa, a monster in ancient Greek mythology, famously had on her head in place of hair, lending the object its intriguing name.  The legend of Medusa also held that anyone who saw her face would transform into stone. In this case, you can feast your eyes without fear on the centre of the merging galaxies, a region known as Medusa's eye. All the cool gas pooling here has triggered a burst of star formation, causing it to stand out brightly against the dark cosmic backdrop. The Medusa merger is located about 130 million light-years away in the constellation of Ursa Major (The Great Bear).
This galaxy is known as the Medusa merger—or the less exciting name, NGC 4194. It formed when a young galaxy consumed a smaller gas-rich system and threw out streams of stars and dust into space. Those streams resemble the writhing snakes that Medusa, a monster in ancient Greek mythology, had on her head in place of hair. The Medusa merger is located about 130 million light-years away in the constellation of Ursa Major (The Great Bear).  ESA/Hubble & NASA, A. Adamo
This system consists of a pair of galaxies, dubbed IC 694 and NGC 3690, which made a close pass some 700 million years ago. As a result of this interaction, the system underwent a fierce burst of star formation. In the last fifteen years or so six supernovae have popped off in the outer reaches of the galaxy, making this system a distinguished supernova factory.
This system consists of a pair of galaxies, dubbed IC 694 and NGC 3690, which made a close pass some 700 million years ago. As a result of this interaction, the system underwent a fierce burst of star formation. In the last fifteen years or so six supernovae have popped off in the outer reaches of the galaxy, making this system a distinguished supernova factory. NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
Located in the constellation of Hercules, about 230 million light-years away, NGC 6052 is a pair of colliding galaxies. They were first discovered in 1784 by William Herschel and were originally classified as a single irregular galaxy because of their odd shape. However, we now know that NGC 6052 actually consists of two galaxies that are in the process of colliding. This particular image of NGC 6052 was taken using the Wide Field Camera 3 on the NASA/ESA Hubble Space Telescope.
Located in the constellation of Hercules, about 230 million light-years away, NGC 6052 is a pair of colliding galaxies. ESA/Hubble & NASA, A. Adamo et al.
Appearing within the boundless darkness of space, the NASA/ESA Hubble Space Telescope’s snapshot of NGC 34 looks more like an otherworldly, bioluminescent creature from the deep oceans than a galaxy. Lying in the constellation Cetus (The Sea Monster), the galaxy’s outer region appears almost translucent, pinpricked with stars and strange wispy tendrils. The main cause for this galaxy’s odd appearance lies in its past. If we were able to reverse time by a few million years, we would see two beautiful spiral galaxies on a direct collision course. When these galaxies collided into one another, their intricate patterns and spiral arms were permanently disturbed. This image shows the galaxy's bright centre, a result of this merging event that has created a burst of new star formation and lit up the surrounding gas. As the galaxies continue to intertwine and become one, NGC 34’s shape will become more like that of an peculiar galaxy, devoid of any distinct shape.  In the vastness of space, collisions between galaxies are quite rare events, but they can be numerous in mega-clusters containing hundreds or even thousands of galaxies.
NGC 34 lies in the constellation Cetus, or “The Sea Monster.” This image shows the galaxy’s bright center, a result of a galactic collision that created a burst of new star formation and lit up the surrounding gas. ESA/Hubble & NASA, A. Adamo et al.
 

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Jessica Boddy

Associate Editor of Special Projects

Jess Boddy started at PopSci as an Editorial Assistant back in 2019. Since then, she’s helped edit the science section, produced the wellness series Test Dummy, and now, as Special Projects Editor, she leads audio projects.