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Stars' X-Ray Super Flares Believed to Aid Planet Formation

Astronomers say violent solar x-ray outbursts that would scorch Earth today paradoxically could have protected the planet billions of years ago while it was forming. A survey of very young stars by an orbiting NASA observatory finds that many like the Sun produce massive flares that help planets survive destruction during their emergence.

Without a time machine as a tool, astronomers observe other stars like the Sun at various stages of their existence to guess what might have occurred in our solar system's early years or what its future might be like.

An international team used the U.S. Chandra X-Ray Observatory to peer at several young suns in the constellation Orion. They saw 27 of them about the same mass as our Sun, ranging in age from one to 10 million years, an age when planets form from the disks of gas and dust that swirl around the stars.

During a two-week period, these young stars displayed enormous x-ray eruptions that Pennsylvania State University astronomer Eric Feigelson says dwarf anything seen from the Sun today in size, energy, and frequency.

"These flares are really incredibly strong. Even the faintest of the x-ray events seen with Chandra is more powerful than the strongest event seen on the contemporary Sun today. They also occur incredibly frequently. Every few days, there is a big flare in the baby sun while similar events occur on the Sun today once every few years," he explained.

Some flares extended 10 times the radius of the stars, reaching the inner edge of the planet forming disks around them.

Astronomers infer that our Sun was just as energetic in its youth, but say it's a good thing it is far less so in middle age. Today's comparatively mild solar flares can create havoc if they reach our planet by damaging electrical circuits aboard satellites and aircraft and shutting down parts of the electrical grid on the ground. But much more powerful ones would be incinerating.

Yet theorists believe they were useful at the time of planet formation. Their recent work suggests that huge x-ray flares can create turbulence when they strike the gaseous planet-forming disks. According to Scott Wolk of the Harvard-Smithsonian Center for Astrophysics, such turbulence is thought to have influenced the position of Earth and its sister rocky planets Mars, Venus and Mercury as they formed billions of years ago, keeping them at a safe distance from the Sun.

"Such flares would have had a profound effect on the material in the solar system and could even have helped protect Earth from rapidly spiraling in towards the Sun and being destroyed," he noted.

NASA scientist Michael Salamon likens the process to a boat being cast away by waves in a storm.

"It's really remarkable how the early x-ray history of the Sun could have played a very profound role in our existence today," he explained.

Even giant gas planets like Jupiter benefited, because the turbulence is thought to have given their inner rocky cores time to accumulate their surrounding gaseous outer layers.

The astronomers found during their Chandra study that young Orion constellation stars with smaller masses than our Sun produced less energetic flares than the bigger sun-like stars. Does this mean the smaller suns inhibit the development of their planets?

Again, Eric Feigelson of Pennsylvania State University.

"I think that is a good question, but this more theoretical interpretation has not been addressed yet in a study," he added.