Astronomers from SRON have discovered mysterious pulses that are being emitted by an extremely magnetic star. The magnetic star, a magnetar, emits the pulses as very high energy X-rays. The astronomers made their observations using the ESA space telescopes INTEGRAL and XMM-Newton and the NASA satellite RXTE.

Magnetars zijn de sterkste magneten in het heelal (beeld: ESA)

Lighthouse

Magnetars are small compact neutron stars with a magnetic field that is one billion times stronger than what can be artificially made on Earth. They are the strongest magnets in the universe. They have a mass one-and-a-half times that of the Sun but this is squeezed into a sphere with a radius of 10 kilometres. How they form exactly is a mystery. As they emit enormous quantities of energy in the form of X-rays, they have a lifespan of only 10,000 years. The magnetars rotate like mad around their axes, as a result of which they regularly sling a bundle of radiation into space like a lighthouse emitting a beacon of light. Although these X-rays to not reach the Earth's surface, they are nevertheless visible in space with the aid of an X-ray telescope.

INTEGRAL is sinds oktober 2002 operationeel in de ruimte (beeld: ESA)

Film

‘By converting the observations from INTEGRAL, XMM-Newton and RXTE into a type of short film, we could see how the characteristics of the X-rays changed over the course of time,’ explains Den Hartog. The characteristics of the radiation were found to drastically change during the rotation of the magnetar. Den Hartog: ‘Three different processes were found to be taking place in the magnetar that gave rise to three different pulses’. For the time being, the meaning of this Morse code remains a mystery. This is why astronomers look with high expectations forward to the first data of space observatory GLAST due for launch by NASA on the 2nd of June. GLAST will study the high energy radiation from the universe in detail.

Een Delta II raket wordt gereed gemaakt voor de lancering van GLAST (beeld: NASA)

Peter den Hartog defended his PhD thesis entitled ‘Non-thermal X-ray emission from Anomalous X-ray Pulsars’ on Wednesday 21 May 2008 at the Universiteit van Amsterdam.