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Magnetars and Exoplanets

By Dave Reneke

News from the space and astronomy communities around the world.

“Impossible” Magnetar Found

A new star has been discovered that almost defies description. It has a magnetic field 20,000 times stronger and a mass 35 times than that of the Sun. That’s nearly 10 times stronger than what has been detected around any other high mass star! It’s no surprise that astronomers call it a “magnetar”.

Magnetars are characterised by their extremely powerful magnetic fields, which can reach the order of 10 GT. These magnetic fields are hundreds of millions of times stronger than any man-made magnet and quadrillions of times more powerful than the field surrounding Earth.

Magnetars are the most magnetic objects ever detected in the universe. At a distance halfway to the Moon, a magnetar could strip information from the magnetic stripes of all the credit cards on Earth.

The newly discovered star, NGC 1624-2, lies about 20,000 light years from Earth in the constellation Perseus. It’s extreme mass makes it bright and hot and likely to burn out relatively quickly after a lifetime of about 5 million years. That’s a mere one-tenth of 1% of the Sun’s current age at midlife!

While the discovery will almost certainly shed light on the role that a star’s magnetism plays in the evolution of stars and their galaxies, the fundamental processes that produce the magnetic fields of massive stars still remain poorly understood. “Magnetic fields of this strength are extremely rare,” said Gregg Wade, lead author and astronomer at the Royal Military College of Canada. “It’s remarkable. It’s more than four times wider than that of any other comparable massive star, and around 80 times larger.”

The star is both distant and surrounded by dust. To study its light in detail, the team of astronomers monitored the star with the immense light-gathering power of the mirror at the Hobby-Eberly Telescope at the University of Texas.

Observations suggest that the star is rotating quite slowly, taking about 160 Earth days to spin once on its axis. In comparison, it takes the Sun about 25 days. “We think that the star has slowed down because it has to drag its wind around, being bound to the magnetic field,” Wade said. “This is something that has to be tested, but it looks very likely.”

No doubt the most important question astronomers seek to answer is: “What’s the origin of magnetism in massive stars, and where do the fields come from?”

Oddball Exoplanets

Astronomers have discovered a veritable “rogues gallery” of odd and unusual exoplanets, from scorching hot worlds with molten surfaces to frigid ice balls. While the hunt continues for the elusive “twin Earth”, new research reveals that life may actually be able to survive on some of the many exoplanetary oddballs that exist.

“When we’re talking about a habitable planet, we’re talking about a world where liquid water can exist,” explains Stephen Kane, a scientist with the NASA Exoplanet Science Institute in California. “A planet needs to be the right distance from its star: not too hot and not too cold.” Astronomers commonly call this the “habitable zone” around a star.

Kane and fellow scientist Dawn Gelino have created a resource called the Habitable Zone Gallery (www.hzgallery.org), which calculates the size and distance of the zone for each exoplanetary system that has been discovered and shows which exoplanets orbit in this so-called “Goldilocks” zone.

Not all exoplanets have Earth-like orbits that remain at a fairly constant distance from their stars. One of the unexpected revelations of planet hunting has been that many planets travel in very oblong, eccentric orbits that vary greatly in distance from their stars.

“Planets like these may spend some but not all of their time in the habitable zone,” Kane says. “You might have a world that heats up for brief periods in between long, cold winters, or might have brief spikes of very hot conditions.”

Although planets like these would be very different from Earth, this might not preclude them from being able to support alien life. Scientists have found microscopic life forms on Earth that can survive all kinds of extreme conditions.

Kane and Gelino’s research suggests that the habitable zone around stars may be larger than once thought, and that planets that might be hostile to human life might be the perfect place for extremophiles, like lichens and bacteria, to survive.

Many life-harbouring worlds may not be planets at all, but rather moons of larger gas giants like Jupiter in our own solar system. “A moon of a planet that is in or spends time in a habitable zone can be habitable itself,” Kane said.

Kane is quick to point out that there are limits to what they can presently determine about the habitability of already discovered exoplanets. Still, the research suggests that habitability might exist in many forms in the galaxy, not just on planets that look like our own.

David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at www.davidreneke.com