It has been described as hiding
in plain sight, a planet 10 times as massive as Earth and orbiting
the Sun beyond Neptune. Predicted in a series of studies over the last few
years, Planet Nine of the solar system — if it exists — continues to elude, and
yet intrigue, with clues suggesting that it is indeed out there.
The latest pointer comes
from another object in the outer Solar System, called 2015 BP519.
This one is certain: it was discovered during the international project Dark
Energy Survey. In a paper on a preprint archive reporting the discovery, a
large team of scientists has concluded that 2015 BP519 “adds to the
circumstantial evidence for the existence of this proposed new member of the
Solar System”.
The object orbits the Sun at
an extreme tilt — its orbital plane is inclined at 54° to that of the eight
planets. This, the researchers believe, is probably because of the influence
of the gigantic Planet Nine. Otherwise, the extreme inclination of the
BP519 orbit did not make sense in simulations of the known Solar System.
“The computer simulations we use
takes all objects in the Solar System and evolves them forward or backwards in
time, and looks at how the orbits of the objects change over time,” lead author
Juliette Becker, a PhD student at the University of Michigan, told The Indian
Express by email. “When we ran a simulation without Planet Nine, we found it
was very hard to make objects like BP519. When we ran a different simulation
including Planet Nine, we found that it was very easy to make objects like
BP519,” she said.
Over the years, scientists have
sought to explain other puzzling aspects of the solar system by attributing
these to the influence of Planet Nine. In a 2016 paper in The Astronomical
Journal, California University of Technology researchers Konstantin Batygin and
Michael Brown made out a case for the existence of the planet by arguing that
it could be responsible for the peculiar alignment of objects in the Kuiper
belt, an expansive field of icy debris on the outskirts of the Solar
System.
The same year, another Caltech
team attributed a well-known feature of the Solar System to Planet Nine. The Sun’s
equatorial plane is aligned six degrees off from the orbital plane of the
planets, something that had long puzzled scientists. According to the
Caltech team, it is not the Sun that is out of alignment but the eight
planets; Planet Nine’s mass has caused their orbital plane to wobble.
Batygin and Brown had predicted
that Planet Nine’s gravity would push Kuiper belt objects into higher
inclinations. Asked about the latest findings, Batygin said by email: “The
discovery of Becker et al is a fantastic result — they have detected the
first highly inclined Kuiper belt object that securely resides in the Planet
Nine-dominated domain of the Solar System. I could not be happier about
their detection.”
All the evidence, however strong,
does not prove conclusively that Planet Nine exists. How much longer will that
take? Batygin said: “The false-alarm probability with the current set of
objects is about 0.1%. Additional findings will lower this value even further.”
But Becker felt: “The only way to prove the existence of Planet Nine is to
directly detect it (to take a picture and see it there). All these pieces of
indirect evidence will help us figure out where to look for it, though!”
Credit: Indian Express Explained (http://indianexpress.com/article/explained/planet-nine-new-evidence-strong-but-not-proof-solar-system-5193774/)
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