ALMA spots newborn star with growing circumstellar disk

TOKYO, March 3 (UPI) -- Astronomers in Japan have identified a newborn star enveloped by a growing blanket of gas.

Using the Atacama Large Millimeter Array, an observatory in Chile, a team of Japanese researchers were able to observe gas accumulating around TMC-1A.

Astronomers detailed their observations this week in the Astrophysical Journal.

The baby star and its newly formed circumstellar disk are located 450 light-years from Earth in the constellation Taurus.

Stars are born within thick clouds of interstellar gas, and the growth of newborn stars is fueled by surrounding gas. But gas cannot directly feed a star, it first circles into a disk-like formation. The disk then nurtures the star to maturity.

Like planet formation, star formation is only partially understood. Astronomers aren't entirely sure when and how circumstellar disks begin to form during the star formation process.

Researchers hope that as radio telescope technology continues to advance, they will be able to hone in more intimately on the star formation process.

"The disks around young stars are the places where planets will be formed," lead researcher Yusuke Aso, a grad student at the University of Tokyo, said in a press release. "To understand the formation mechanism of a disk, we need to differentiate the disk from the outer envelope precisely and pinpoint the location of its boundary."

For the first time, astronomers were able to identify the transition region that forms the boundary between the fast-rotating inner disk of gas and the outer gas envelope. The outer "infalling" envelope accrues gas from the cosmic surroundings, while the faster spinning inner disk feeds the star.

By calculating the speed of the inner disk's rotation, scientists were able to calculate the mass of TMC-1A. The baby star is 0.68 times the mass of our sun.

The ALMA data also showed that gas on the outside the transition region moved faster toward the center of the star -- drawn by the baby star's gravity -- while the inner gas' descent was slowed. Researchers believe the pull of gravity is diminished by the star's magnetic field.

"We expect that as the baby star grows, the boundary between the disk and the infall region moves outward," Aso said. "We are sure that future ALMA observations will reveal such evolution."