Australasian Science: Australia's authority on science since 1938

Huge Solar Storms to Impact Earth

By David Reneke

Dave Reneke brings news from the space and astronomy communities around the world.

Huge Solar Storms to Impact Earth
Beware the solar maximum – that’s the dire warning from senior space agency scientists. They believe the Earth will be hit with unprecedented levels of magnetic energy from solar flares after the Sun wakes from a deep slumber sometime around 2013. National power grids could overheat and air travel could be severely disrupted while electronic items, navigation devices and major satellites could stop working.

Severe solar flares, the strongest in 100 years, could result in widespread power blackouts and leave cities without critical communication signals for long periods of time, warns Dr Richard Fisher, director of NASA’s Heliophysics Division.

The solar storms that will cause the Sun to reach temperatures of more than 10,000°F occur only a few times over a person’s life. Every 22 years the Sun’s magnetic energy cycle peaks while the number of sun spots and solar flares hits a maximum level every 11 years. This is the solar maximum you hear so much about. And of course there is a solar minimum – that’s what we’re in now.

Nasa said the super storm would hit like “a bolt of lightning”, causing catastrophic consequences for the world’s health, emergency services and national security unless precautions are taken. Communication devices such as satellites and SatNavs through to air travel and our banking system will be at risk. Anything we rely on that is sensitive to magnetic fields, like computers and iPods, could be affected.

“We know it is coming but we don’t know how bad it is going to be,” Fisher said. “Systems will just not work. The flares change the magnetic field on the Earth and it’s rapid, just like a lightning bolt. That’s the solar effect.”

A space weather conference in Washington DC attended by Nasa scientists, policy-makers, researchers and government officials was told of similar warnings. One thing is certain, large areas will be without power and essential services, and to repair that damage will be hard as it takes time. The Sun has plenty of that, another five billion years worth in fact!

Planetary Misfit or Par for the Course?
Astronomers are technically trained, pragmatic people, constantly prepared to expect the unexpected. It’s a logic honed from many years peering through telescopes at strange things in the night sky. They’ve seen and photographed some of the most indelible sights in the heavens – colliding galaxies, magnetars, hypervelocity stars and many more examples of nature’s quirkiness. Now they say they’ve spotted a planet with a tail.

But hang on, planets don’t have tails! Well, they didn’t, until the 21st century rolled around. We’ve got new technology now, much better telescopes, and have come to expect the unforeseen. But this discovery was like nothing anybody had ever dreamed of ever seeing – a planet with a distinct and definitive tail.

Astronomers using NASA’s Hubble Space Telescope have confirmed the existence of a baked object that could be called a “cometary planet”. The giant gas planet, named HD 209458b, is orbiting so close to its star that its heated atmosphere is escaping into space. While it’s been speculated that stars can blast away planets’ masses, this is the first confirmation that atmospheric stripping is a real phenomenon. And since HD 209458b is a pretty typical “hot Jupiter” – the nickname for close orbiting gas giants – it’s almost certain that all hot Jupiters have comet-like tails.

Observations taken with Hubble’s Cosmic Origins Spectrograph (COS) suggest that powerful stellar winds are sweeping the cast off atmospheric material behind the scorched planet, funnelling it into a previously assumed comet-like tail. The planet, located 153 light years from Earth, weighs slightly less than Jupiter but orbits 100 times closer to its star than the Jovian giant. This roasted, rocky world zips around its star in a short 3.5 days; for comparison, our fastest planet, Mercury, orbits the Sun in 88 days.

This extrasolar planet is one of the most intensely scrutinised because it is the first of the few known alien worlds that can be seen passing in front of, or transiting, its star. Jeffrey Linsky, an astronomer at the University of Colorado, and his team used COS to analyse the planet’s atmosphere during transiting events to determine its structure and chemical makeup by sampling the starlight that passes through it.

The dip in starlight is usually very small, about 1.5%. But when the planet’s atmosphere is added, the dip jumps to a whopping 8%, indicating a bloated atmosphere. Early results show the presence of the heavy elements carbon and silicon in the planet’s super-hot 2000°F atmosphere. This is assumed to be a by-product of the star’s heat dredging up the heavier elements, allowing them to escape the planet.

The COS data also showed gas escaping at high velocities, with a large amount of it flowing forward at more than 35,000 km/h. Now, like a thrilling dime store novel, the mystery is starting to untangle. It’s likely that this large gas flow is swept up by the stellar wind to form the comet-like tail trailing the planet. It’s simply the most logical conclusion.

Hubble’s newest spectrograph has the ability to probe a planet’s chemistry at ultraviolet wavelengths not accessible to ground-based telescopes. An earlier scan in 2003 showed an active, evaporating atmosphere, and a comet-tail-like structure was suggested as a possibility. But back then Hubble wasn’t able to obtain the spectroscopic detail necessary to show a tail, or an Earthward-moving component of the gas, during transits. The instrumental sensitivity just wasn’t available back then.

Although this extreme planet is being roasted by its star, it won’t be destroyed anytime soon. “It will take about a trillion years for the planet to evaporate,” Linsky said. It’s unclear how long the superheated alien world’s “tail” is or how long it’s been losing mass, but it’s almost certain that the erosion process has been happening for at least several million years.

Among the more than 400 planets found beyond our solar system there are volcanic super-Earths, gas giants that dwarf Jupiter, and worlds with multiple sunsets. Astronomers think that massive hot Jupiters are born far away from their stars and approach them gradually during eons of orbiting.

Many unanswered questions remain about the properties of exoplanets, such as the details of their composition and their likelihood of possessing moons. Another question is whether they might support life. Several large planets do have orbits in their parent star’s habitable zone, where it should be possible for Earth-like conditions to prevail. If these planets also have large moons, the moons might be a more plausible location for life.

Are Comets Wanderers from Another Star System?
Comets, long-lost members of the solar system’s fragmentary birth, have always been a mystery. In the Middle Ages they were seen as portents of disaster, invoking dire warnings of fire, flood, disease and pestilence. Some religious groups even believed they were the dearly departed souls of their loved ones making their way to Heaven.

These days we know them more as a fascination to look up at in the night sky, to photograph and marvel at. But, where did they come from? That’s a good question, and the answer may not be from where you think.

Along with asteroids they make up the flotsam and jetsam of our solar system. Astronomers believe that they originated great distances away, travelling to the inner solar system from that frozen region outside Pluto called the Oort cloud, halfway to the nearest star. They are the icy counterparts of asteroids impregnated with life-giving water-ice, and perhaps the building blocks of life.

New computer simulations show that many comets – including some famous ones – came from even farther out. They may have been born in other solar systems. Many of the most well-known comets, including Hale-Bopp, Halley, and most recently McNaught, may have formed around other stars before becoming gravitationally captured by our Sun when it was still in its birth cluster.

Computer simulations by scientists like Dr Hal Levison from the Southwest Research Institute in Boulder, Colorado, show that the Sun may have captured small icy bodies from its sibling stars while still in its star-forming nursery cluster.

The researchers investigated what fraction of comets might be able to travel from the outer reaches of one star to the outer reaches of another. The simulations imply that a substantial number of comets can be captured through this mechanism, and that a large number of Oort cloud comets come from other stars.

The results may explain why the number of comets in the Oort cloud is larger than models predict. “We can conclude that more than 90% of the observed Oort cloud comets have an extra-solar origin,” Levison said.

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