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The Solar System's Missing Planet Has Only One Place Left to Hide

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Feb 21, 2024, 12:02:34 PMFeb 21

The Solar System's Missing Planet Has Only One Place Left to Hide
The Solar System's Missing Planet Has Only One Place Left to Hide

19 February 2024
Dark Planet In Space
Artist's illustration of Planet Nine. (ESO/Tomruen/nagualdesign)
A recently submitted study to The Astronomical Journal continues to
search for the elusive Planet Nine (also called Planet X), which is a
hypothetical planet that potentially orbits in the outer reaches of the
solar system and well beyond the orbit of the dwarf planet, Pluto.

The goal of this study was to narrow down the possible locations of
Planet Nine and holds the potential to help researchers better
understand the makeup of our solar system, along with its formation and
evolutionary processes.

So, what was the motivation behind this study regarding narrowing down
the location of a potential Planet Nine?

Dr. Mike Brown, who is a Richard and Barbara Rosenberg Professor of
Astronomy at Caltech and lead author of the study, tells Universe Today,
"We are continuing to try to systematically cover all of the regions of
the sky where we predict Planet Nine to be. Using data from Pan-STARRS
allowed us to cover the largest region to date."

Pan-STARRS, which stands for Panoramic Survey Telescope and Rapid
Response System, is a collaborative astronomical observation system
located at Haleakala Observatory and operated by the University of
Hawai'I Institute of Astronomy with telescope construction being funded
by the U.S. Air Force.

For the study, the researchers used data from Data Release 2 (DR2) with
the goal of narrowing down the possible location of Planet Nine based on
findings from past studies.

In the end, the team narrowed down possible locations of Planet Nine by
eliminating approximately 78 percent of possible locations that were
calculated from previous studies.

Additionally, the researchers also provided new estimates for the
approximate semimajor axis (measured in astronomical units (AU)) and
Earth-mass size of Planet Nine at 500 and 6.6, respectively.

So, what are the most significant results from this study, and what
follow-up studies are currently being conducted or planned?

"While I would love to say that the most significant result was finding
Planet Nine, we didn't," Dr. Brown tells Universe Today. "So instead, it
means that we have significantly narrowed the search area. We've now
surveyed approximately 80% of the regions where we think Planet Nine
might be."

In terms of follow-up studies, Dr. Brown tells Universe Today, "I think
that the LSST is the most likely survey to find Planet Nine. When it
comes online in a year or two it will quickly cover much of the search
space and, if Planet Nine is there, find it."

LSST stands for Legacy Survey of Space and Time, and is an astronomical
survey currently scheduled as a 10-year program to study the southern
sky and take place at the Vera C. Rubin Observatory in Chile, which is
presently under construction.

Objectives for LSST include studying identifying near-Earth asteroids
(NEAs) and small planetary bodies within our solar system, but also
include deep space studies, as well. These include investigating the
properties of dark matter and dark energy and the evolution of the Milky
Way Galaxy. But what is the importance of finding Planet Nine?

Dr. Brown tells Universe Today, "This would be the 5th largest planet of
our solar system and the only one with a mass between Earth and Uranus.
Such planets are common around other stars, and we would suddenly have a
chance to study one in our own solar system."

Scientists began hypothesizing the existence of Planet Nine shortly
after the discovery of Neptune in 1846, including an 1880 memoir
authored by D. Kirkwood and later a 1946 paper authored by American
astronomer, Clyde Tombaugh, who was responsible for discovering Pluto in

More recent studies include studies from 2016 and 2017 presenting
evidence for the existence of Planet Nine, the former of which was
co-authored by Dr. Brown.

This most recent study marks the most complete investigation of
narrowing down the location of Planet Nine, which Dr. Brown has
long-believed exists, telling Universe Today, "There are too many
separate signs that Planet Nine is there. The solar system is very
difficult to understand without Planet Nine."

He continues by telling Universe Today that "…Planet Nine explains many
things about orbits of objects in the outer solar system that would be
otherwise unexplainable and would each need some sort of separate

"The cluster of the directions of the orbits is the best know, but there
is also the large perihelion distances of many objects, existence of
highly inclined and even retrograde objects, and the high abundance of
very eccentric orbits which cross inside the orbit of Neptune. None of
these should happen in the solar system, but all are easily explainable
as an effect of Planet Nine."

Does Planet Nine exist and where will we find it in the coming years and
decades? Only time will tell, and this is why we science!

This article was originally published by Universe Today. Read the
original article.
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