Goofy galaxy spins in wrong direction

NGC 4622 is more than 100 million light-years from Earth.

By Richard Stenger
CNN Sci-Tech

(CNN) -- A galaxy captured by the camera of the Hubble Space Telescope seems to be rotating in the direction opposite of what it should, astonished astronomers announced this week.

Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy, known as NGC 4266, has two leading outer arms that point toward the direction of the galaxy's rotation, according to Hubble researchers.

"NGC 4622 suggests that maybe people do not know all that there is know about spiral structure yet. Our study may lead to a new understanding of spiral arm production in galaxies," scientists Ron Buta and Gene Byrd said in an e-mail to CNN. A Hubble observatory photo shoot indicated which edge of the galaxy tilts closer to the Earth, allowing the astronomers to determine the spin of the galactic oddball.

"I believe this kind of structure is rare, if not unique, among the relatively small number of galaxies we can see with sufficient detail that we could detect it," said Keith Noll, another Hubble scientist.

This high-resolution image, besides showing the reverse spin of the galaxy, unveils the blue bursts of recently formed stars in the outer pair of galactic arms.

A closer inspection reveals another enigma: a trailing inner arm that wraps around the galaxy in the opposite direction of its rotation, just like conventional arms of spiral galaxies.

"It is pretty clear that there are both clockwise and counter-clockwise spiral arms, so something funny is going on," Noll said.

What could make it comport itself so strangely? That its two outer arms are lopsided suggests that something major disturbed it. It could have hit and ingested a much smaller galaxy, the astronomers theorized.

"What caused us to suspect that a collision or merger might be involved in this galaxy is that we found a strong, sharp dust lane right across the nucleus of the galaxy. We suspect a companion was destroyed in the merger and that the dust lane is the surviving evidence," Buta and Byrd said.

NGC 4622 resides 111 million light-years away in the direction of the constellation Centaurus.

Galaxies, which consist of stars, gas and dust, rotate extremely slowly. Our sun, located in one of the spiral arms of the Milky Way, goes around the galactic center about once every 250 million years.