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EI2GYB > ASTRO 08.10.21 09:33l 71 Lines 3770 Bytes #999 (0) @ WW
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Subj: This may be the first exoplanet found orbiting three stars
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Sent: 211008/0728Z @:EI2GYB.DGL.IRL.EURO #:15689 BPQ6.0.22
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This may be the first exoplanet found orbiting three stars
Thanks to disruptions in the disk around a young star system, astronomers think
they've uncovered the first planet orbiting a stellar trio.
Residing 1,300 light-years away in the famous constellation Orion the Hunter is
the triple-star system GW Orionis. Of its three stars, two closely orbit each
other, while a third orbits the pair. These stellar triplets are young, still
surrounded by a disk of dust, gas, and debris left over from their formation.
And this disk, called a protoplanetary disk, has caught astronomers' attention
for several reasons - not least of which because it might harbor the first
known exoplanet orbiting a trio of stars.
The disk around GW Orionis consists of three concentric rings of material, none
which align with any of the orbits of the system's three stars. Furthermore,
the innermost ring doesn't even align with the other rings, and it strangely
tilts and wobbles as it orbits. And finally, there's a big gap carved in the
disk, which indicates that most the material there has been cleared out.
Of course, researchers want to know what's going on in GW Orionis. And a new
paper published Sept. 17 in Monthly Notices of the Royal Astronomical Society
may hold the answer: There's a so-called circumtriple planet (or planets)
forming within the disk, orbiting all three stars at once.
Making space
Gaps in protoplanetary disks are well known for hinting that planets are
forming within them. As planets pull in nearby gas and dust to grow, they
naturally clear out their surroundings. But in this case, researchers weren't
sure whether the disk's strange behavior should be attributed to a fledgling
planet or to the whirling activity of the three stars within.
As it turns out, based on 3D modeling of the system, those three stars can't
produce enough torque to clear out the gap in the disk we see. Instead, the
researchers say, that gap is most likely due to at least one Jupiter-sized
planet forming there. If confirmed, it would be the first ever exoplanet found
to orbit three stars. (Although planets have been discovered in just over 30
triple systems to date, none of these worlds orbits all three stars.)
The supposed planet or planets would orbit the system about 100 astronomical
units (AU) from the center (1 AU is the average Earth-Sun distance). The stars
themselves are much closer together. The tightly orbiting pair are separated by
just 1 AU, while the third star orbits some 8 AU from the center of the system.
Because this research only provides indirect evidence for the first
circumtriple planet, the next step will be actually spotting the strange world.
Unfortunately, the authors conclude, that's tricky when dealing with a system
as complex as GW Orionis. Still, more observations are coming down the pike.
And just maybe they will reveal a glimpse at a truly unique young world.
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