24 January 2016

Planet X found

The term "Planet X" has a variety of meanings and uses.  After the discovery of Neptune, Percival Lowell "proposed the Planet X hypothesis to explain apparent discrepancies in the orbits of the giant planets, particularly Uranus and Neptune, speculating that the gravity of a large unseen ninth planet could have perturbed Uranus enough to account for the irregularities."
Today, the astronomical community widely agrees that Planet X, as originally envisioned, does not exist, but the concept of Planet X has been revived by a number of astronomers to explain other anomalies observed in the outer Solar System. In popular culture, and even among some astronomers, Planet X became a stand-in term for any undiscovered planet in the outer Solar System, regardless of its relationship to Lowell's hypothesis.  
This week, good evidence was reported for the existence of such a previously-undiscovered planet.  I've seen it referred to as Planet X or as Planet IX.

The embedded video gives a broad overview.  This article in Science provides more details.  Even more amazing than the existence of the planet is its extraordinary orbit:

In the schematic, the entire known solar system is represented by the small blue circle in the center (magnified in an offset in the upper part of the image).
The orbit of the inferred planet is similarly tilted, as well as stretched to distances that will explode previous conceptions of the solar system. Its closest approach to the sun is seven times farther than Neptune, or 200 astronomical units (AUs). (An AU is the distance between Earth and the sun, about 150 million kilometers.) And Planet X could roam as far as 600 to 1200 AU, well beyond the Kuiper belt, the region of small icy worlds that begins at Neptune’s edge about 30 AU.
Mind-boggingly awesome.


  1. 1. is planet x 'really' in our solar system, or just happens to be a random chunk of space junk that is around? depending on how how look at, you could start finding planet xi, xii, etc.

    2. the 15k year orbital period and the time when this puppy is closet to earth - does that time period correspond to any 'anomalies' that have occurred - ice ages, magnetic pole reversals, massive earthquakes, etc.


    1. 1) If it orbits our sun, it is in the solar system - that's how the term is defined.

      2) At its closest it is out way further than Neptune or Pluto. Don't expect anomalies.

  2. "Finding" will happen when the planet is observed. The team who have narrowed down its size and orbital options don't expect it to be found for years.

    1. I also remain skeptical, but will be more than happy to be proven wrong. The search space is incredibly large. We will see.

  3. Not a planet.
    The definition is a body massive enough to collapse itself into a sphere (probably true here--check), orbit the Sun (check), and be in a stable, long-term orbit so that it has cleared any other large objects (not a check). Kuiper Belt Objects--like Pluto--are only in temporary, irregular orbits which have not cleared other objects away.

    1. When you're talking 14,000 year plus orbits, clearing the path of their orbit may be an unrealistic expectation for a defining characteristic. By the time they clear a full orbit, new junk may have taken up position. They may have to re-address this requirement for planetary definition.

      For those that hope this would get Pluto back as a planet, you're out of luck. It's too small too and I don't think they'll ever change that as it would jump our current planets from 8 to, I beleive, 39 if they defined "planet" as Pluto's size or larger. The count doesn't take "planet 9" into account as it is not yet confirmed or anything else they've found over the last year.


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