Here's a new way to find planet 9 if it exists
Artist's rendering of Planet 9, a hypothetical world. Credits: Caltech/R. Hurt (IPAC)
In a recently published article, an astronomer describes a new way to unearth the elusive planet 9 if it exists. The only condition is that this hypothetical object be surrounded by several moons. Explanations.
An elusive world
The search for Planet 9 began as early as 2016. At the time, two Caltech astronomers presented evidence that six objects beyond Neptune's orbit were clustering together in strange ways. The furthest points of their orbits were indeed located much further from the Sun than the closest points of their orbits. According to calculations, the gravitational pull of an invisible planet about four times larger and about ten times more massive than the Earth could then explain the eccentricity of these orbits.
Despite everything, this hypothetical planet 9 remains elusive. Some also point out that its supposed presence mentioned in several studies could be the result of a statistical anomaly or a selection bias on the part of astronomers. Others have even speculated that this mysterious object may in fact be a primordial black hole the size of a grapefruit .
The main challenge of this hunt for planet 9 remains its theoretical distance. In 2016, the authors of the study had estimated that it could evolve anywhere between 400 and 800 AU from the sun (one AU equals the Earth-sun distance). At such a distance, the surface of this object would be around -233°C. For comparison, Pluto is positioned between 30 and 50 AU from our star.
Even so, some are still looking for ways to locate this planet. In a new paper posted on the arXiv preprint server , astronomer Man Ho Chan suggests isolating the presence of this object by detecting the heat signatures of all its potentially captured moons.
Use heat signatures
According to the astronomer, such a large planet nestled somewhere between the inner Oort cloud and the Kuiper belt, beyond Neptune , would indeed have no great difficulty in capturing smaller objects. Remember that in our solar system, only Mercury and Venus do not have a moon. Even non-planetary bodies have them, like Pluto or some asteroids.
That being said, satellites captured by a planet tend to have elliptical and irregular orbits , which means that the gravitational forces acting on the moons change as they move closer or farther apart. But these ever-changing stresses warm the moons from within. This is called tidal warming . This heat is then dissipated in the form of thermal radiation.
According to the astronomer's calculations, some of these moons could be heated up to 100 Kelvin at certain points in their orbit. If so, their heat signatures could be detectable by the powerful ALMA radio telescope array, located in Chile.
Also according to calculations, based on what we know of objects moving in the supposed region of planet 9, it should capture a reasonable number of moons, perhaps as many as twenty with a diameter of 140 kilometers or more . . What facilitate the search for thermal signatures.
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