BBC Sky at Night Magazine
Debate over solar bubble’s shape deepens
Is the heliosphere shaped like a bulging croissant?
Space scientists have been arguing over whether the heliosphere – the bubble created by the solar wind – is shaped like a comet, a croissant or a ball for several years. Now, new simulations suggest the real shape could actually be a hybrid.
Astronomers have long assumed the heliosphere is swept back by the Sun’s motion through the Galaxy, forming a comet-like tail. However, when Voyager 1 passed through the outer Solar System in 2015, its readings suggested the ‘comet’ is actually a crescent with two tails. Then, scientists using Cassini measurements suggested it was spherical.
The new paper by astronomers from Harvard and the University of Michigan combines the two spacecraft measurements to create a new view of the heliosphere as a bulging croissant, halfway between crescent and sphere. The view is controversial though, and debate over the true shape of the Solar System continues. www.bu.edu/csp