Until Pluto was downgraded to a dwarf planet (something that still rankles many people), some scientists were of the view there is a tenth planet in the solar system. With the change to the status of Pluto, the same considerations continue in relation to the mystery of ‘planet nine’.
Planet Nine?
Planet Nine is possible planet located in the outer region of the Solar System. The reason why astronomers have speculated that the planet exists for decades is due to unexplained gravitational effects. These effects may account for an unusual clustering of orbits for a group of extreme trans-Neptunian objects (eTNOs). These are bodies located out past Neptune, which orbit the Sun. These objects are positioned at distances averaging more than 250 times that of the Earth.
Among the extreme trans-Neptunian objects are three high-perihelion objects classified as sednoids: 90377 Sedna, 2012 VP113, and 541132 Leleākūhonua. These are Pluto-like objects far out in the Kuiper Belt, a ring of icy rocks out past Neptune.
Black hole?
Now the possibility has been raised that the ‘ninth planet’ may not be a planet at all. Harvard University scientists have described the possibility that the observed orbital evidence for Planet 9 is actually a primordial black hole, one with a horizon size no larger than a grapefruit, and possessing a mass 5 to 10 times that of Earth.
Most black holes develop when stars exhaust their nuclear fuel and collapse into a singularity. However, in the early time of universe it is theorized that high-density regions of space may have formed smaller singularities without beginning as a star – and such a space could exist on the fringe of the Solar System.
This would not be possible to detect directly, because it would be completely dark. However, it could be detectable via the Vera C. Rubin Observatory, when it runs the Legacy Survey of Space and Time (LSST) project.
Vera C. Rubin Observatory
The Rubin Observatory has a wide-field reflecting telescope with an 8.4-meter primary mirror that will photograph the entire available sky every few nights. This is coupled to a 3.2-gigapixel camera, which is the world’s largest digital camera ever fabricated for optical astronomy.
New evidence
The new method to search for black holes in the outer solar system, and which might resolve the planet nine conundrum, is based on examining the flares that result from the disruption of intercepted comets.
The process will be able to detect, or conversely, to rule out trapped planet-mass black holes to around one hundred thousand astronomical units.
According to one of the researchers, Amir Siraj: “If the existence of Planet Nine is confirmed through a direct electromagnetic search, it will be the first detection of a new planet in the solar system in two centuries, not counting Pluto.”
Alternatively, the evidence might point to the existence of a proto-black hole.
Research paper
The research has been published in The Astrophysical Journal Letters, and the paper is titled “Searching for Black Holes in the Outer Solar System with LSST.”
Essential Science
This article forms part of Digital Journal’s long running Essential Science column, where a topical science subject is examined each week.
Last week we continued with coronavirus news, looking at whether there was sufficient evidence to indicate whether SARS-CoV-2 was becoming more infectious through a mutation of its spike protein.
The previous week we considered new climate change evidence into the South Pole. With this, researchers have discovered that the South Pole is warming at a rate three times above the global average. This has occurred across the past 30 years.
