Things Getting Windy on T Tauri Star

Things are stirring up around a T Tauri star, the infant equivalent of our own Sun, as astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have observed what may be the first-ever signs of windy weather around the small solar system. The finding may help explain why some T Tauri stars have disks that glow oddly in infrared light while others shine in a more expected fashion.

T Tauri stars are the equivalent of stars like our Sun, surrounded by the raw materials that make up both rocky and gaseous planets. Though nearly invisible in optical light, these disks shine in both infrared and millimeter-wavelength light.

"The material in the disk of a T Tauri star usually, but not always, emits infrared radiation with a predictable energy distribution," lead author Colette Salyk said in a press release. "Some T Tauri stars, however, like to act up by emitting infrared radiation in unexpected ways."

Astronomers believe that winds from within T Tauri stars' protoplanetary disks may explain these differing infrared signatures. However, these winds - which have important implications in planet formation - have thus far never been detected.

Using ALMA, Salyk and her colleagues looked for evidence of a possible wind in AS 205 N - a T Tauri star located 407 light-years away in the constellation Ophiuchus. They focused on the distribution of carbon monoxide around the star, an excellent tracer for the molecular gas that makes up stars and their planet-forming disks. The study confirmed that gas indeed was emanating from the disk's surface the first clear evidence that wind was present.

But the properties of the wind, however, did not exactly match expectations. Salyk and her team speculate that the discrepancy could be due to the fact that AS 205 N is actually part of a multiple star system, suggesting that the gas is leaving the disk's surface because it's being pulled away by the binary companion star rather than ejected by a wind.

"We are hoping these new ALMA observations help us better understand winds, but they have also left us with a new mystery," said Salyk. "Are we seeing winds, or interactions with the companion star?"

The research team plans to continue studying these winds using ALMA to figure it out. Their findings were published in the Astrophysical Journal.