OUR young sun may have been a late bloomer. The first reading of charged particles streaming from a younger solar twin shows that this constant particle flow, or wind, is rather wimpy. If our baby sun behaved like this, its timidity perhaps bought time for early Mars to play host to water.
Other young, sun-like stars are much more active than our middle-aged sun, blasting out more flares and high-energy radiation. For our sun, an increase in activity is often linked to a stronger wind, so astronomers suspected that these highly active stars would have very strong winds, and that our sun had a stormier youth too. That's why the latest find was a shock.
"Winds are hard to detect directly," says Brian Wood at the US Naval Research Laboratory in Washington DC. Instead, his team looked for the effect of stellar winds colliding with surrounding gas. That creates an ultraviolet glow which intensifies as winds get stronger (Astrophysical Journal Letters, doi.org/q33).
Using the Hubble Space Telescope, the team checked out a star that is almost exactly like our 5-billion-year-old sun but is just 500 million years old. The star shows lots of flares and other activity – but its wind is about half as strong as the sun's is today.
Other look-a-likes, about a billion years old, have much stronger winds, with around 10 times the oomph of the modern sun's output. This suggests a scenario where the stars start sleepy, ramp up and then settle back down by middle age.
If the young sun was sluggish, it might have given early Mars the time it needed for water, and perhaps life, to take hold. Evidence from NASA's rovers strongly supports the notion that the cold, dry Red Planet was once warm enough for rivers and oceans.
If so, it probably had a thicker atmosphere that vanished, perhaps stripped away by a strengthening solar wind, says Wood. NASA's MAVEN spacecraft is en route to Mars to study when and how the atmosphere was lost, including the possible influence of the sun.
This article appeared in print under the headline "Newborn sun's weak winds a boon to Mars?"
- New Scientist
- Not just a website!
- Subscribe to New Scientist and get:
- New Scientist magazine delivered every week
- Unlimited online access to articles from over 500 back issues
- Subscribe Now and Save
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
