Dying Galaxy Bleeds Fireballs into Space During its Death Throes

Scientists have discovered some amazing things in our universe. Now, they've uncovered a bright dwarf galaxy relatively close to Earth's Milky Way in its death throes as it trails fireballs across the sky.

Many galaxies in our universe have stopped creating stars, essentially rendering them lifeless. Star formation is at the heart of galactic vitality, and many galaxies are veritable star factories. Yet this dying galaxy, known as IC3418, is now almost completely out of gas and, in consequence, is no longer forming stars at its core.

The galaxy is located deep inside the Virgo Cluster, a mass of about 1,000 galaxies and the nearest large galaxy collection to the group that includes the Milky Way. Researchers estimate that the core of the studied galaxy stopped making stars between 200 and 300 million years ago. While the galaxy may have run out of gas and stopped forming stars at its core long ago, though, researchers found that its distinctive fireball-dotted trail shows evidence of recent star formation--a surprising phenomenon.

In fact, these trails of fireballs are probably the result of the process that's killing the galaxy, called "ram pressure stripping." In this process, the interaction of gases in the space between galaxies generates an enormous pressure that can force out an individual galaxy's interior gas while leaving existing stars untouched. Ram pressure essentially pushes gas away from the galaxy and forms stars that are left behind.

"If you hold popcorn and unpopped kernels of corn in your hand and stick it out the car window as you drive, the wind caused by the car's motion through the air will blow away the popcorn but leave the denser, unpopped kernels in your hand," said Jeffrey D.P. Kenney of Yale University, the principal researcher, in a news release. "This is like the gas clouds in galaxies being blown out of the galaxy by the wind of cluster gas, while the denser stars remain behind."

In order to examine this galaxy a bit better, the researchers used WIYN 3.5-meter telescope in Arizona and the twin Keck 10-meter telescopes in Hawaii to perform both optical imaging and spectroscopy techniques.  They found that the galaxy is actually very near death. Star formation is occurring at the heads of the fireballs, yet gas is quickly being stripped away; this, in turn, is killing the galaxy.

"It's gratifying to find a clear example of an important process in galaxy evolution," said Kenney in a news release.

The findings have shown researchers a bit more about the death of galaxies. In addition, they reveal a bit more about the universe and how it works, showing what events are responsible for the present state of galaxies.

The findings are published in The Astrophysical Journal.