It's one of the Solar System's most intriguing questions in the last five years: Is there
a giant planet out there in the cold, dark reaches of our Solar System, orbiting at a
distance so great that it would take 20,000 years to complete?
The answer has eluded scientists, but a recent study has discovered what could be evidence
of the mysterious hypothetical object's existence.
Using data from the Infrared Astronomical Satellite (IRAS), the first infrared space
telescope, astronomer Michael Rowan-Robinson conducted a search for a proposed 10th planet
in 1983; Pluto was still a planet at the time.
Rowan-Robinson did not discover a new planet, and by 1991, he was very certain that such
a planet did not exist, at least not in the area of the sky where he looked.
However, since then, new regions of the sky have been proposed as possible homes for a
mysterious planet known as Planet Nine.
Rowan-Robinson reviewed the 38-year-old data after a recent study identified new potential
hiding sites for Planet Nine.
He discovered three potential infrared sources that he believes could be Planet Nine.
While he acknowledges that the chances of the object being Planet Nine are 'not overwhelming',
he believes it is worth checking.
If Planet Nine exists, it would be five to ten times the size of the Earth and orbit
the sun at a distance of up to 800 times that of the Earth.
To put things in perspective, the Earth is currently 92 million miles from the sun, or
one astronomical unit (AU), whereas Pluto, which was reclassified from a planet to a
dwarf planet in 2006, is 40 AU, or 3.7 billion miles away.
Its tremendous distance and small size make it difficult to find; it's too far from the
sun to be lighted by it, so it's only visible in blips, and it is theorized by the impact
its gravity has on objects beyond Neptune.
Caltech astronomers Mike Brown and Konstantin Batygin revived interest in the potential
'Super Earth' planet after discovering small objects in the Kuiper Belt that were orbiting
as though pushed about by the gravity of a larger object.
Several theories have been proposed to explain Planet Nine's peculiar behavior, including
the possibility that it is a grapefruit-sized black hole.
However, the idea of a 'Super-Earth', a type of planet found in many other solar systems,
is prevalent, attracting astronomers to the cause.
IRAS was a spacecraft that orbited for ten months starting in January 1983 and took a
far-infrared survey of 96% of the sky during that time.
This area of the electromagnetic spectrum is ideal for locating small, cool things like
Planet Nine, but the data was obtained long ago when scientists weren't looking for the
distant world.
As a result, Rowan-Robinson chose to re-analyze the data using parameters compatible with
Planet Nine.
Of around 250,000 point sources detected by the satellite, only three are of interest
as potential Planet Nine candidates.
In the months of June, July, and September of 1983, the satellite detected what appeared
to be a moving object across the sky, even though it was in a region of space near the
galactic plane.
This means that any data points from that location are affected by galactic cirrus,
which are filamentary clouds that shine in the far infrared.
And so, according to Rowan-Robinson, what could be Planet Nine could just as easily
be noise from these clouds.
If the IRAS data points are correct, Planet Nine is up to five times the mass of Earth
and orbits the sun at a distance of 225 AU.
Its orbital period, or how long it takes to go around the sun, may be determined by having
three-time points showing it moving across the sky.
This information can then be used to determine where it is today and seek it in other data
sources, such as the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), which
was launched in 2008.
Pan-STARRS data analysis hasn't yielded any encouraging outcomes so far.
In fact, scientists have been unable to locate the potential planet.
Dynamical research is needed to see if such an entity is consistent with the ephemerides
of other Solar System objects and if it may explain the clustering of the orbits of Kuiper
belt dwarf planets.
Although the IRAS detections are not of the best quality, it might be worthwhile to search
at optical and near-infrared wavelengths in an annulus of radius 2.5 to 4 deg centered
on the 1983 position.
This candidate may be ruled out if radio or other observations confirmed the actuality
and stationarity of the IRAS sources at the 1983 positions.