Invalid and gigantic, a galaxy shaped like a tadpole

A team of Israeli, American and Russian researchers has identified a huge but deeply damaged galaxy.

The galaxy, which looks a lot like a tadpole, is over 300 million light years from Earth. Noah Brosch, principal investigator of the Florence Observatory and George Wise of Tel Aviv University, described it as being "disturbed" because it was clearly subjected to enormous external forces.

Usually, disturbed galaxies are relatively small, because their stars have been incorporated into a nearby more massive galaxy or ejected en masse in space as a result of a titanic collision between two star systems.

The latest discovery, however, will most likely prompt a reconsideration of the constraints for the survival of such systems.

"We found an exceptional relic of a disturbed galaxy," says Brosch.

The structure, which is part of a group of small galaxies called Compact Group 98 of Hickson, is huge. From a total length of about one million light years, it is ten times larger than the Milky Way.

"What makes this object extraordinary is that the tail alone is nearly 500,000 light-years long," says Michael Rich, co-author of the University of California Los Angeles.

"If it was at the distance from the Andromeda galaxy, which lies about 2.5 million light years from Earth, it would reach one-fifth of the way to our own milky way." . "

Brosch and his colleagues suggest that the galactic tadpole formed as a result of destruction by a previous star-filled dwarf galaxy by the gravitational force of two larger galaxies and a dramatic redistribution of its components.

"The extragalactic tadpole contains a system of two very close" normal "galaxy discs, each about 40,000 light years away," explains Brosch. "Together with other nearby galaxies, galaxies form a compact group."

Scientists remain, this group is far from being an established system. All members of Hickson's Compact 98 group are expected to merge into a giant galaxy within a billion years or so. At this point, the extragalactic tadpole will likely become a cosmic frog.

The research is published in the Monthly Notices from the Royal Astronomical Society.