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by Paul Ratner
18
February, 2021
from
BigThink Website
Backwards planets
in
double star system.
Illustration: Christoffer Grønne.
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Astrophysicists find a very rare system with two
exoplanets orbiting their star backwards.
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The star system K2-290 is 897 light years away.
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In our Solar System, all the planets revolve in the
same direction as the rotation of the Sun.
A unique
star system
where exoplanets
orbit their star
backwards
located by
researchers...
Astrophysicists
discovered a very rare planetary system 897 light years away which
features two
exoplanets orbiting their star
backwards...
This unexpected
arrangement is due to the tilting of the protoplanetary disk in
which the planets were formed.
The researchers found that the two planets in the
K2-290 system orbit around the star
in almost the opposite direction as the star's rotation around its
own axis.
In our Solar System, by
comparison, all the planets revolve in the same direction as the
rotation of the Sun. K2-290 A's rotational axis is tilted by
approximately 124 degrees in contrast to the orbits of the planets.
The international research team was led by Maria Hjorth and
Simon Albrecht from the Stellar Astrophysics Centre of
Aarhus University in Denmark, and also involved scientists from
Princeton University, Pennsylvania State University, University of
Toronto, and Tokyo Institute of Technology.
This actually isn't the first time a "backwards" planetary system
like this has been spotted. One was sighted over 10 years ago.
But, as one of the
study's authors Joshua Winn from Princeton University
explained in a
press release,
"this is a rare case
in which we think we know what caused the drastic misalignment,
and the explanation is different from what researchers have
assumed might have happened in the other systems."
A protoplanetary disc was
twisted almost 180° before planet formation.
Illustration:
Christoffer Grønne.
The unusual formation of the planets was caused by the
protoplanetary disk - a disk of
material that spins around a young star for several million years
after the star's birth.
Normally, this spin is
going in the same direction as the star but the gravitational force
from a neighboring star can tilt the disk, which is what happened in
this case.
Another author, PhD student Emil Knudstrup from Aarhus
University, shared what drew him to this work:
"The idea that
planets travel on wildly misaligned orbits has fascinated me
throughout my graduate study.
It is one thing to
predict the existence of these crazy orbits, so very different
from what we see in the Solar System. It is quite another thing
to participate in actually finding them...!"
Check out the paper "A
Backward-spinning Star with two Coplanar Planets"
published in the Proceedings of the National Academy of Sciences
(PNAS).
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