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Galaxy’s Arms are Rotating Backwards

10 Jan , 2008 by

As galaxies rotate, their spiral arms usually sweep back, trailing behind the rotation of the galaxy. But astronomers have found a galaxy that defies this convention, with its arms opening outward in the same direction as the rotation of the galaxy’s disk.

The galaxy, known as NGC 4622, lies 200 million light years away in the constellation Centaurus. A team of American astronomers analyzed images of the galaxy, and discovered that it has a previously hidden inner counter clockwise pair of spiral arms.

“Contrary to conventional wisdom, with both an inner counter-clockwise pair and an outer clockwise pair of spiral arms, NGC 4622 must have a pair of leading arms,” said Dr. Gene Byrd from the University of Alabama. “With two pairs of arms winding in opposite directions, one pair must lead and one pair must trail. Which way is which depends on the disk’s rotation. Alternatively, the inner counter clockwise pair must be the leading pair if the disk turns counter clockwise.”

This isn’t the first time the team announced their findings that NGC 4622 had a leading pair of spiral arms. Other astronomers were skeptical of the result, since the galaxy disk is only tilted 19 degrees from face-on, and clumpy clouds of dust could confuse the results.

The researchers came back and used two different independent techniques to verify the direction the arms are spinning.

Further observations are coming, since images from the Hubble Space Telescope revealed a dark dust lane in the centre of the galaxy. This suggests that NGC 4622 may have consumed a smaller companion galaxy, and this could help explain where the additional spiral arms came from.

Original Source: University of Alabama News Release


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dustin
Guest
dustin
January 11, 2008 8:14 AM

Two quich questions please, When do you think that galaxy NGC 4622 may have consumed another galaxy? And if it did consume another galaxy how would it have gained additional spiral arms?

Rick Eyerdam
Guest
Rick Eyerdam
January 11, 2008 8:20 AM

So which rules of gravity and motion apply and which are being discarded in this scenario?

John Mendenhall
Member
John Mendenhall
January 11, 2008 8:35 AM

Say, fellow posters, take a look at this week’s articles, starting with this one and working back. If this keeps up, Fraser can shut down the ATM section, the mainstreamers are doing ATM themselves, including ideas that would have been laughed off ATM. And the mainstreamers have the observations to back up their claims. Now for some independent verification.

My favorite so far is the intermediate black holes from globular clusters.

RUF
Guest
RUF
January 11, 2008 9:38 PM

It is a beautiful, delicate looking galaxy. A merger probably happened long ago. Knowing if there are rapid star-forming areas in the galaxy may answer how long ago a merger took place. Are there any Spitzer images of NGC 4622?

John Tomassoni
Guest
John Tomassoni
January 15, 2008 1:53 PM
For me, I have to take the position that it is impossible for a galaxy to have two sets of arms that are connected, to be rotating in opposite directions. If the opposing spin of one set of arms was really due to an assumed collision with another (unknown) body, as suggested by the U of Alabama team, it would be most likely that the resulting motion of the contacted arm would be very unlike the opposing arm — but in reality, the arm motion of each side are quite similar to each other (nearly symmetrical). It would be most likely that the resulting motion of one arm, if contacted by an alien body, would be, at least,… Read more »
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