Our Unneighborly Neighborhood: New Technique to Reveal Solar System’s Secrets

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The observable universe is a ginormous realm, whose 42.3 billion light year radius is riddled with galaxy filaments and voids. Suspended in one of the trillions of galaxies is an infinitesimal speck, a speck consisting of what humans may refer to as our neighborhood: the . Juxtaposed to the cosmic scale, the solar system does indeed seem speck-like; however, this approach fails to acknowledge the mysteries lurking in our own territory. The ’s oceans, and even more so the outer regions of our solar system, are largely unknown, which is in part a limit of current technology but even more a consequence of the immensity of these areas. The solar system is truly a large spectacle.

Recognized in this way, the solar system presents itself as a playground for Sherlock Holmes, a village with features so suspicious they warrant thorough analysis. And indeed, one of the more elusive areas compelling astronomers to begin a Sherlockian investigation would be trans-Neptunian objects, or TNOs. This acronym is a designation assigned to any member of our solar system whose orbit is beyond that of Neptune. would be a TNO, for instance, as would Sedna. Due to their sheer distance from the Sun, their relatively small size, and lengthy orbital periods, most have successfully evaded our catalogues. These objects are faint in both the infrared and optical spectra; and while their orbits tend to be highly elliptical, meaning their closeness to the Earth undergoes fluctuations of a few AU (one AU is around 150 million kilometers), one fluctuation cycle may require 100s of years to complete. A patient astronomer may construct a backyard observatory and survey the skies for “wandering stars” each evening, but he will likely be reduced to dust before he detects any noticeable movement.

The outer solar system is all the more intriguing in the midst of tentative conclusions formed by interpretation of the sparse data currently available. The supposed clustering of perihelia, which denotes the point of an object’s orbit where the object is closest to the Sun, of a variety of TNOs, as well as the nature of these particular objects’ orbital eccentricities, have led to a hypothesis. This clustering occurring by chance, argue and , would mean a probability of 0.007%. Some sort of massive gravitational influence would be likelier to perturb these TNOs into their current configuration. The research pair then utilizes the approximate properties of the TNOs to determine ranges for Nine properties, such as mass and orbital period. The task now is to search for cosmic entities with these characteristics, better refining the state of the catalog, and searching for new TNOs that may also be clustered in this manner.

With plenty of prompts to encourage the TNO search, a group of astronomers consisting of , , and tried concocting a new method to find TNOs, fine-tuning it with data already collected. The group created an that, with only one parameter input ( distance), could identify TNO candidates by computing the object’s geocentric coordinates (position relative to the Earth) and heliocentric coordinates (position relative to the Sun). A relatively close cosmic object in Earth’s evening sky will exhibit what is known as parallax as Earth completes its orbit around the Sun. As a consequence of this parallax, a nearby star may appear to wobble during a period of one year, and a moving object may have  “loop-de-loops” in its path. These precise loops are what inspired Ptolemy’s “epicycle” model of the universe, but contemporary astronomers are aware that this strange change in an object’s movement is simply a product of our moving planet. Converting these coordinates into a heliocentric form will generate a linear curve, as there are no actual wobbles in TNO’s orbit, and with this new structure of the data the algorithm effectively creates a best-fit distance of the object in question.

Using data from the Wide-Field Infrared Survey Explorer () data, the group applied their algorithm to search for the TNO Makemake, which was discovered by Brown et. al in 2005 and has an average orbital distance of 45 AU. The authors note the initial number of data points to be scanned was 280515, and they managed to reduce this number to 4836 following the use of a velocity filter (which discriminates objects with angular velocities consistent with TNOs) and “mean coordinate” computations. Thereafter executing the code, the results consisted of “all detections of Makemake from the data set. We therefore conclude that our approach allows for the discovery of Makemake based on WISE data alone” (7).

While the authors report no detection of Planet Nine within the WISE data catalog, given the ranges of this hypothetical planet’s physical properties, they hope their code will supplement the search for any TNO amidst background noise Planet Nine included. My only hope is, if the investigation proves a success, that the finders name it Pluto, thus reviving the nostalgic elementary school acronym of the solar system planets. At the least, Sherlock would be proud.





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Post Author: Kim Conger

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