Giant eruption reveals

dead star

BY DR EMILY BALDWIN

ASTRONOMY NOW

Posted: 17 June, 2009

X-rays from an enormous stellar eruption which arrived at the Earth in August last year originated from a rare group of dead star known as a magnetar.

Magnetars are the most intensely magnetized objects in the Universe, boasting magnetic fields some 10,000 million times stronger than our planet Earth. To put that in context, if a magnetar existed half way between the Earth and the Moon, its magnetic field would wipe the details off every credit card on Earth.

Magnetars are the most intensely magnetised objects in the Universe. Image: NASA.

“Magnetars allow us to study extreme matter conditions that cannot be reproduced on Earth,” says Nanda Rea from the University of Amsterdam, who led the team that performed the research.

Fortunately magnetar SGR 0501+4516 lies 15,000 light years away, presenting no danger to us. Traveling through space for many thousands of years, its X-rays were felt by the NASA-led Swift satellite on 22 August 2008. Along with ESA’s XMM-Newton and Integral space observatories, an intense observation campaign began to record the four month long outburst, during which many smaller bursts were also detected.

Outbursts from a magnetar are thought to occur when its intense magnetic field becomes unstable and pulls the star’s crust apart, allowing matter to spew out and tangle up in the magnetic field lines. This can result in an even more unstable configuration of the magnetic field lines, releasing even more energy. Integral detected one such outburst five days after the main eruption, which persisted for 10 days and beyond the energy range that XMM-Newton can see, the first time such transient X-ray emission was detected during the outburst.

High energy X-ray emission from SGR 0501+4516 was observed by Integral. Image: Credits: ESA/INTEGRAL/IBIS-SIGRI (Rea et al. 2009).

Since magnetars are extremely rare – just 15 are known in our Galaxy – there is no conclusive evidence for how they form. There are two prevailing theories, however, one is that it is the tiny core left behind after a highly magnetic star has died; the other is that during the death of a normal star, its tiny core is accelerated, providing a dynamo that strengthens its magnetic field, turning it into a magnetar.

“If we could just find a magnetar in a cluster of highly magnetic stars, that would prove it [the first idea],” says Rea. The hunt is on, and in the case of SGR 0501+4516, the team will use XMM-Newton to observe this curious object again next year, when they hope to see it in a quiescent state so they can study the calm after the storm.

Our latest 132-page Astronomy Now special edition is an extravaganza of astronomy for the year ahead, with a complete 30-page guide to observing the planets, moon, meteor showers, two solar eclipses, and the deep sky in 2010.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

This special publication features the photography of British astro-imager Nik Szymanek and covers a range of photographic methods from basic to advanced. Beautiful pictures of the night sky can be obtained with a simple camera and tripod before tackling more difficult projects, such as guided astrophotography through the telescope and CCD imaging.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

Explore the Universe with these new versions of the award-winning Starry Night Software. Available now from the Astronomy Now Store.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

Astronomy Now is pleased to announce the publication of Exploring Mars. The very best images of Mars taken by orbiting spacecraft and NASA's Spirit and Opportunity rovers fill up the 98 glossy pages of this special edition!
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

This new poster features some of the best pictures from NASA's amazing Mars Exploration Rovers Spirit and Opportunity.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE