Mathematical calculations and computer simulations disprove current dogma regarding the formation of Earthlike planets around binary stars, meaning sunsets like that witnessed on Luke Skywalker’s mythical home planet may be more common than we thought.
Researchers from the University of Utah set out to demonstrate that despite current beliefs, rocky planets like our own Earth could in fact form encircling two stars, creating the kind of twin sunsets witnessed in ‘Star Wars.’ Previously, only gas-giants, devoid of life, were thought capable of forming under such conditions, yet these new findings suggest solid planets in this arrangement are not only out there, but may exist in abundance.
In a statement, Ben Bromley, an astrophysicist with the University of Utah, and Scott Kenyon from the Smithsonian Astrophysical Observatory, said their study concluded that “Tatooine sunsets may be common after all,” and that according to their scenario, “planets are as prevalent around binaries as around single stars.”
A spinoff of initial work with the reclassified dwarf planet Pluto and its major moon Charon, the pair’s interest was sparked by the binary arrangement of the four additional planets orbiting each. In this study, the team used mathematical models to work out the story of how planetesimals, rocks the size of asteroids that bind together to make planets, form around binary stars.
What they found was that these growing rock clusters rely on oval orbits to avoid collisions that would otherwise destroy the budding planet. This is in contrast to the orderly, concentric circles followed by planetismals circling a single star, naturally positioned to avoid crashes.
“Planets form like dust bunnies under your bed, glomming together to make larger and larger objects. When planets form around a binary, the binary scrambles up the dust bunnies unless they are on just the right orbit,” explained Kenyon.
Though they say their findings didn’t extend to full star formation, the study showed that oval-orbits could allow planetesimals to exist for tens of thousands of years.
“The planets, when they are small, will naturally seek these oval-shaped orbits and never start off on circular ones…their orbits can be nested and they won’t bash into each other. They can find orbits where planets can form,” added Bromley.
More than 1,000 planets encircling other stars have been found using NASA’s Kepler space telescope, but none quite like Tatooine. Seven gas giants were found near binary stars, but rocky planets in the same setup will be harder to find.
Bromley says their study does something “everyone else says is impossible,” proving these observed giants could have actually formed where they are, as opposed to forming further out from their center stars and later migrating to their current location.
Submitted for review to Astrophysical Journal, the paper is currently available online on the preprint website ArXiv.
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