Ice world with insane 20,000-year orbit discovered in solar system

The wide-field view of the sky around the bright star Alpha Centauri © Wikipedia
An icy planet with a staggering 20,000-year orbit has been discovered passing through our solar system, leading to the re-emergence of theories touting the existence of the fabled and mystical Planet 9.

L91, as the icy rock is called, is an enigma defying previously established gravitational patterns, and its discovery has added to mounting evidence that there are gravitational disruptions going on beyond what we can see, according to scientists working on the Outer Solar System Origins Survey.

Although L91 orbits our solar system’s sun, it never comes closer than 50 astronomical units, and at its farthest extreme it is a whopping 1,430 AU away. Each AU equals the distance between the Sun and Earth.

“It’s right at the limit of what we can detect,” said Michele Bannister, an astrophysicist at Queen’s University, Belfast, who introduced L91 to the world at the American Astronomical Society’s Division for Planetary Science meeting held there on Monday.

Wandering bodies like L91 have contributed to the idea that planetary systems aren’t static. It used to be the common school of thought that every celestial body in our solar system has followed a relatively unchanged path for the more than four billion years since its birth.

It has only been in the past decade that scientists have learned that even Jupiter and Saturn constantly wobble in distance from the sun.

At present, scientists still can’t determine L91’s size, and have conflicting views on what is disrupting its orbit. One theory is that it is influenced by Neptune.

L91 is believed to have been born with a far less exotic orbit, but current knowledge of Neptune’s trajectory, when taken together with L91’s, shows the orbit might have evolved over time to pass through the Oort cloud, then change again from interacting with something in our galaxy at large. This over time nudged L91 into its current orbit, the Neptune theory goes.

Other scientists from places as prestigious as Caltech still insist on a more mysterious explanation, but one they maintain is no less plausible than Neptune. Konstantin Batygin believes the Neptune analogy “is not needed,” and points to the arcane Planet 9 – a supposed ice giant with an orbit far more distant than Neptune’s.

Batygin and another Caltech astronomer, Mike Brown, believe Planet 9’s gravitational pull is behind the trajectories of the minor planets orbiting beyond Neptune. They jointly published their hypothesis in January of this year.

The discovery of L91 comes amid a whole series of recent scientific revelations about space – from our plans to colonize Mars in the near future, to the discovery of Earth-like and potentially habitable planets within our galactic reach.

Perhaps even more exciting is the next step, which involves photographing these worlds and learning more about their climates and chemical compositions. The privately-funded Project Blue – the first telescope that hopes to photograph planets in the habitable zone of our space neighborhood – may play a key role in this. Our nearest hope is in the Alpha Centauri constellation, which is a modest 4.22 light years from Earth and home to the most recently discovered potentially habitable planet.