October 12, 2012
Stellar Winds Of Two Massive Stars Tracked Using X-Rays
[Watch the Video: X-ray Satellites Monitor the Clashing Winds of a Colossal Binary]
[Watch the Video: Simulation of Colliding Stellar Wind Binary][Watch the Video: Simulation of Binary Star System]
Lee Rannals for redOrbit.com — Your Universe Online
Astronomers have X-rayed the stellar winds of two massive stars that are orbiting around one another.
Stellar winds can trigger the collapse of surrounding clouds of gas and dust to form new stars, and can also blast the clouds away before they have the chance to get started.
The European Space Agency (ESA) said astronomers used XMM-Newton and Swift to find a "Rosetta Stone" for these winds in a binary system known as Cyg OB2 #9. This system's radio emission could only be explained if the object was not a single star, but two.
At the time of the discovery, there was no evidence of stellar winds from the two stars colliding, despite the X-ray signature of this phenomenon being expected. This signature could only be found by tracking the stars as they reached their closest point on their 2.4-year orbit around each other.
As the telescopes viewed the event, the stellar winds slammed together at millions of miles per hour, creating hot plasma at a million degrees.
The telescopes were able to record a four-fold increase in energy compared with the normal X-ray emission seen when the stars were further apart on their elliptical orbit.
“This is the first time that we have found clear evidence for colliding winds in this system,” Yael NazÃ© of the UniversitÃ© de LiÃ¨ge, Belgium, and lead author of the paper reported in Astronomy & Astrophysics, said in a press release. “We only have a few other examples of winds in binary systems crashing together, but this one example can really be considered an archetype for this phenomenon.”
The style of the collision in Cyg OB2 #9 remains the same throughout the stars' orbit, despite the increase in intensity as the two winds meet.
“In other examples the collision is turbulent; the winds of one star might crash onto the other when they are at their closest, causing a sudden drop in X-ray emission,” NazÃ© said in the release.
“But in the Cyg OB2 #9 system there is no such observation, so we can consider it the first ℠simple´ example that has been discovered — that really is the key to developing better models to help understand the characteristics of these powerful stellar winds. ”