Free Astronomy Magazine September-October 2022

38 SEPTEMBER-OCTOBER 2022 ASTRO PUBLISHING T he images that allowed the dis- covery of the dwarf planet Sedna. This object could be the most mas- sive of those most directly per- turbed by the hypothetical large planet that would exist at the outer borders of our solar system. [Palomar Observatory] T hese images from November 5, 2012, spaced about 2 hours apart from each other, allowed for the discovery of 2012 VP113, the most distant TNO known to date, with aphelion at 446 AU and an orbital period of 4274 years. 2012 VP113 appears to move slowly between the stars and galaxies in the background. [Scott Sheppard/Carnegie Institution for Science] known giant planets in our solar sys- tem. It is reasonable to expect that the flux peak of the hypothetical Planet Nine would also fall within that range. But why start a search of this type if, as mentioned above, the positions in the sky of the known planets are now harmonizing with those calcu- lated? One would assume that the existence of a large planet on the outer borders of the solar system would no longer seem necessary. In reality, this is not the case. Since 2012, astronomers have known that a non-negligible number of discov- ered Trans-Neptunian objects (TNOs, a category that includes dwarf plan- ets, large asteroids and cometary nuclei) share the properties of hav- ing their perihelion near the ecliptic and on the same side of the Sun, or- bits oriented in the same direction and inclined by about 30°, and they are physically grouped. In short, at least a dozen TNOs, including the dwarf planet Sedna, are concen- trated in a statistically very unlikely way. Supercomputer simulations performed in 2015 by Konstantin Batygin and Mike Brown (California Institute of Technology) show that there is only one chance in nearly 15,000 that the orbital clustering of those TNOs is random. That scenario could instead be explained by one January to November 1983, and by the AKARI Space Telescope, opera- tional from February 2006 to No- vember 2011. In addition to the temporal separation, these two data- bases were chosen for the relative homogeneity of the data they con- tain: both cover far-infrared wave- lengths close to the flux peaks of