Telstra has revealed the addition of almost one million new mobile services in the six months to December 2011, but Sensis revenues plummeted 24 percent in 12 months.
Herbig stars - large stars emitting X-rays even though our understanding of their structure suggests they shouldn't - have been known for a couple of decades. One theory was that the X-rays come from companion stars in orbit around them.
Data collected by XMM-Newton has allowed an international team led by Manuel Güdel and Alessandra Telleschi of the Paul Scherrer Institut in Switzerland to suggest a neater solution.
Observations of AB Aurigae, a Herbig star in the Taurus-Auriga cloud - showed that its X-ray emissions have the same periodicity as the optical and ultraviolet light coming from it. "Finding the same periodicity confirms that the X-rays are coming from AB Aurigae and not from a companion star," says Güdel.
The data also showed that the gas emitting the X-rays was much cooler than expected.
An important clue came from XMM-Newton's spectrometer, which showed the X-rays were coming from high above the star. Güdel, Telleschi and the team suggest that a magnetic field within the star funnels its stellar winds together, and the resulting collisions create the X-rays.
The next job is to study other Herbig stars to see if this model also fits them.
David Bass
| For the fourth year in a row, IDC has placed content security provider Websense (NASDAQ: WBSN) at the top of the IDC Worldwide Web Security 2011 –…
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