Scientists Reopen 360-Million-Year-Old Galaxy-on-Galaxy Violence Cold Case

Some say it was NGC 5291’s fault for not properly yielding to the oncoming galaxy.


About 200 million light-years away, a hazy elliptical galaxy called NGC 5291 was involved in an interstellar collision with another galaxy. Some say it was NGC 5291’s fault for not properly yielding to the oncoming galaxy; others say NGC 5291 did nothing wrong. But regardless of who’s to blame, the crash resulted in a huge amount of gas and matter being flung out and slowly accreting into a ring around NGC 5291. Some of that material shaped up into dwarf galaxies of their own.

Scientists at the European Southern Observatory’s Very Large Telescope, located at the Paranal Observatory, have just made public a slew of new images they’ve collected that show off this one-of-a-kind region of the universe — including the first high-detail glimpse of the largest dwarf galaxy created by the harrowing collision: NGC 5291N.

Galaxies around the universe, including our very own Milky Way, are thought to have formed in the early days of the universe through the conglomeration of smaller dwarf galaxies. A lot of these smaller dwarf galaxies, if they haven’t already been eaten up by larger stellar bodies, are usually home to very old stars.

Because NGC 5291N was birthed by a cosmic crash of two normal galaxies, however, it only has new stars. It’s not a remnant of the old, dark days of the universe. Moreover, the ESO astronomers observed the dwarf galaxy doing some pretty unique things rarely found elsewhere — including interacting gently with the nearby Seashell Galaxy and emitting unusual amounts of oxygen and hydrogen near its outskirts.

Although systems like NGC 5291 exist elsewhere, most are situated so far off that they’re insanely hard to study. “The characteristics and the proximity of these newly formed dwarf galaxies around the ring allowed us to get insight on the star-formation processes at play inside far-away galaxies,” says astronomer and research lead Jeremy Fensch, based at Paris Diderot University. “The MUSE observation [which revealed the oxygen and hydrogen emissions] was specifically aimed at investigating the ionization state of the gas, which is excited by photoionization from the new stars and maybe also strong shocks.”

Wide-field view of the sky around the galaxy NGC 5291

ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin

“This system might prove to be of interest for the study of the Milky Way, because it was alike this galaxy around 10 billions years ago,” says Fensch. “But strong constraints on the formation of the Milky Way cannot yet be drawn from this study.”

The team hopes to continue a follow up study of the strange gas activity using the Atacama Large Millimeter Array located in Chile.

In the meantime, feast your eyes on more of what the astronomers found when gawking on NGC 5291.