Illuminate a path to find planet nine

The search for Planet Nine – a hypothetical ninth planet in our solar system – could eventually identify the faintest orbital trails in an incredibly dark corner of space.

This is exactly what Yale astronomers Malena Rice and Gregory Laughlin are attempting with a technique that collects scattered light from thousands of space telescope images and identifies orbital paths for previously undetected objects.

“You can’t really see them without using this kind of method. If Planet Nine is out there, it’s going to be incredibly weak, ”said Rice, lead author of a new study that was accepted by the Planetary Science Journal.

Rice, a Ph.D. astronomy student and graduate researcher of the National Science Foundation, presented the findings on October 27 at the annual meeting of the American Astronomical Society’s division for planetary sciences.

The possibility of a ninth planet in Earth’s solar system, located beyond Neptune’s orbit, has gained momentum among astronomers in recent years as they have examined the curious orbits of a cluster of small icy objects in the Kuiper belt. Many astronomers believe that the alignment of these objects – and their trajectories – indicate the influence of an invisible object.

Although the vast majority of the light observed by planets in the solar system is reflected light, the amount of reflected sunlight drops dramatically for a distant planet like Planet Nine, probably 12 to 23 times farther from the Sun than Pluto.

If it exists, planet nine would be a so-called super-Earth. It would have 5 to 10 times the mass of the Earth and be located hundreds of times farther from the Sun than the Earth is and 14 to 27 times farther from the Sun than Neptune, said Laughlin, senior author of the new study and professor. of astronomy in the Faculty of Arts and Sciences.

This is an almost entirely unexplored region of space.

Gregory Laughlin

“This is a region of space that is almost entirely unexplored,” Laughlin said.

To detect otherwise undetectable objects, Rice and Laughlin use a method called “move and stack”. They “move” images from a space telescope – like moving a camera while taking pictures – along predefined series of potential orbital paths. They then “stack” hundreds of these images together in a way that combines their faint light.

Occasionally, light reveals the path of a moving object, such as an asteroid or planet.

Rice said moving and stacking have been used in the past to discover new moons in the solar system. This is the first time it is being used on a large scale to search a large area of ​​space. The images she and Laughlin used came from the Transiting Exoplanet Survey Satellite, a space telescope normally used to search for planets outside our solar system.

The researchers tested their method by successfully searching for light signals from three known trans-Neptunian objects (TNOs). Next, they conducted a blind search of two sectors in the outer solar system that could reveal Planet Nine or any previously undetected Kuiper belt object and detected 17 potential objects.

“If even one of these candidate objects were real, it would help us understand the dynamics of the outer solar system and the likely properties of Planet Nine,” Rice said. “This is compelling new information.”

He is currently working with former Yale Songhu Wang postdoc, a faculty member at Indiana University, to check the 17 candidates using ground-based telescopes.

Laughlin said the successful use of limited-scale displacement and stacking will pave the way for a larger-scale investigation of the outer solar system, which is particularly compelling given the possibility of finding a new planet.