Planets Might Orbit Backward around Odd Star

TOP VIEW: A huge star-forming region is rotating globally in the direction shown by the white arrow. This large region can give birth to multiple stellar systems. MIDDLE VIEW: A detailed view inside the large star-forming region shows three protostars forming as the region collapses. The collapse process is chaotic and can cause eddies, allowing newly-forming stars to rotate in different directions and at different speeds, as shown by the arrows. BOTTOM VIEW: One protostellar cloud collapses further into a disk-like structure that rotates counter-clockwise (white arrows) about the newly-formed protostar. In addition, the protostar siphons off material from a second, passing protostellar cloud rotating in the opposite direction. Because of this, the outer part of the disk rotates clockwise (yellow arrows). Eventually, planets will form from the material in this disk, with the outer planets orbiting the star in the opposite direction from the inner planets. IMAGE CREDIT: Bill Saxton, NRAO/AUI/NSF

A developing star has been found to have two disks of material rotating in opposite directions. The discovery hints at a future solar system with planets going this way and that.

"This is the first time anyone has seen anything like this, and it means that the process of forming planets from such disks is more complex than we previously expected," said Anthony Remijan, of the National Radio Astronomy Observatory.

When stars form, they collapse from a cloud of gas and dust. A ring of leftovers generally develops and rotates in the same direction as the star. From the disk, planets form.

"The solar system that likely will be formed around this star will include planets orbiting in different directions, unlike our own solar system in which all the planets orbit the Sun in the same direction," said study co-leader Jan M. Hollis, of the NASA Goddard Space Flight Center.

The discovery, announced today, suggests the star was born in an unconventional manner. The whole setup sits within a large, star-forming region where chaotic motions cause clouds to rotate in different directions.

"We think this system may have gotten material from two clouds instead of one, and the two were rotating in opposite directions," Remijan said.

There is enough material to form planets from both parts of the disk, Remijan said.

The finding was made with the National Science Foundation's Very Large Array radio telescope. Material moving toward or away from the telescope emits radiation at different frequencies, just as the siren of an ambulance changes pitch when it moves toward and then away from you in what's known as a Doppler shift.

The counter-rotation is not entirely surprising, "since the phenomenon has been previously reported in the disks of galaxies," Hollis said.

The results will be detailed in the April 1 edition of the Astrophysical Journal.

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