A ‘planetary mass object’ may lurk in the outer reaches of our solar system

Planet beyond Solar System

Reports of unknown celestial bodies (read planets) beyond the Kuiper Belt continue to flow in with a new study suggesting presence of a ‘planetary mass object’ in the outer reaches of our solar system.

According to a study published in the Astronomical Journal, this particular object is different from the Planet Nine and is possibly much closer. The study is the result of the work carried out by scientists at University of Arizona who in their paper have presented compelling evidence of a yet-to-be-discovered planetary body that has mass somewhere between that of Mars and Earth.

Astronomers say that this particular ‘planetary mass object’ hasn’t been observed directly but its presence was felt through its influence in controlling the orbital planes of space rocks known as Kuiper Belt objects, or KBOs. Unlike most KBOs, the orbit of these space rocks is tilted away from the invariable plane by about eight degrees. In other words, something unknown is warping the average orbital plane of the outer solar system.

According to the lead author of the study the most likely explanation behind this tilt is the presence of an unseen ‘planetary mass object’ – something as massive as Mars. For the study researchers analyzed the tilt angles of the orbital planes of more than 600 objects in the Kuiper Belt in order to determine the common direction about which these orbital planes all precess. Precession refers to the slow change or “wobble” in the orientation of a rotating object.

The Kuiper Belt lies beyond the orbit of Neptune and extends to a few hundred astronomical units, or AU, with one AU representing the distance between Earth and the Sun. Like its inner solar system cousin, the asteroid belt between Mars and Jupiter, the Kuiper Belt hosts a vast number of minor planets, mostly small icy bodies (the precursors of comets), and a few dwarf planets.

Because a planet, by definition, has to have cleared its orbit of minor planets such as KBOs, the authors refer to the hypothetical mass as a planetary mass object. The data also do not rule out the possibility that the warp could result from more than one planetary mass object.

So why haven’t we found it yet? According to the team, we haven’t found it because we haven’t yet searched the entire sky for distant solar system objects. The most likely place a planetary mass object could be hiding would be in the galactic plane, an area so densely packed with stars that solar system surveys tend to avoid it.

A possible alternative to an unseen object that could have ruffled the plane of outer Kuiper Belt objects could be a star that buzzed the solar system in recent (by astronomical standards) history, the authors said.

Humankind’s chance to catch a glimpse of the mysterious object might come fairly soon once construction of the Large Synoptic Survey Telescope is completed. Run by a consortium that includes the UA and scheduled for first light in 2020, the instrument will take unprecedented, real-time surveys of the sky, night after night.


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