Planet-forming disks of material typically orbit around the equators of stars, but now scientists have discovered such rings can go dramatically awry and encircle the poles of stars instead.
The new study suggests that worlds could exist with polar orbits around pairs of stars, potentially leading to seasons extraordinarily different than Earth’s.
Stars are born within clouds of gas and dust. The gravitational pull of each star draws such material into spiraling orbits around it.
Although clumps of this cloud start off moving in random directions at random speeds, as the cloud collapses, the clumps collide and merge.
The result over time is a flattened disk called a protoplanetary disk that usually spins in the same direction as its star and surrounds the star’s equator.
The planets that emerge from such a disk also typically orbit around the star’s equator, as is the case with the worlds of our solar system.
Prior work found that nearly all young stars are initially surrounded by protoplanetary disks.
In the case of protoplanetary disks around single stars, at least a third go on to form planets, said lead study author Grant Kennedy, an astronomer at the University of Warwick in England.
However, computer simulations have previously suggested that after protoplanetary disks have formed, any extra material they collect can knock them off-kilter.
This could explain why astronomers have detected exoplanets with relatively crooked orbits around stars.
Kennedy and his colleagues focused on so-called circumbinary planets, which orbit around binary stars.
Scientists had suspected that planets around binary stars could become misaligned — instead of orbiting the stars in the same plane in which the stars orbit one another, these worlds could orbit around their poles instead.
Now, Kennedy and his colleagues have detected the first example of a misaligned circumbinary protoplanetary disk. “It’s one of those examples that nature manages to be more creative than we expect,” Kennedy said.
The scientists focused on the quadruple-star system HD 98800, located about 146 light-years from Earth. “If planets were born here, there would be four suns in the sky,” study co-author Daniel Price of Monash University in Australia said in a statement.
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