A semiotic puzzle.
A candidate for a planet in a Trojan orbit - that is, in a position sixty degrees ahead of or behind an planet in the same orbit.
View: https://www.youtube.com/watch?v=Wfrf1qSmKsY
It would be at the Lagrange point L5 of the star.
en.wikipedia.org
There are numerous Trojan-type objects in our own Solar System, most famously the eponymous Trojan asteroids locked with Jupiter.
en.wikipedia.org
This is one notable for being potentially a planet-like object rather than a group of asteroids. Now, an object at an L4 or L5 point would not be rigidly fixed at a point sixty degrees ahead or behind the more massive body but rather orbit a point that is in that position. This could explain why the planet GJ 3470 b, or 'Phailinsiam', is seen to transit its primary while the hypothetical Trojan planet is not - it doesn't stay strictly in the same orbital plane but only orbits a point that is on that plane.
If it exists, is it a planet? Is Phailinsiam? The problem is that this potential object is significantly massive (terrestrial mass at least), as is Phailinsiam (Neptune-like mass).
Pluto was disqualified as a planet by the International Astronomical Union (IAU) because met only two of three criteria: 1) It orbits a star, not a planet; 2) it is a spheroid - but it has
not 3) 'cleared its orbit of other bodies.' This last is very controversial as Jupiter's (and other planet's) Trojan and Greek bodies appear to contradict this and would deprive even Jupiter of planetary status.
So, if this object exists, Phailinsiam may still be a planet and if it is, this object might be too, or may have to be classified as a 'quasi-moon', which will upset a lot of pedants. Earth does itself have 'quasi-moons' which are small, non-spheroidal asteroids that orbit the sun in approximately the same orbit but are bound by their interactions with Earth, at least temporarily.
Now, we can think of Pluto as a large Kuiper-belt object (KBO), like Eris
et al, but that definition depends on their formation and history, not current orbital status. For example, there is strong evidence that Triton, a 'moon' of Neptune, is a sibling of Pluto and originated as a KBO too. As an analogue, evolutionary biology went through a crisis provoked by 'cladistics' when the history of extant species was considered versus their evolutionary history.
evolution.berkeley.edu
For example, consider the class 'pachyderm.' It used to mean a large, mostly hairless grey-skinned mammal living in Africa - hippos, elephants and rhinos. We now know that they are not closely related at all (hippos are in fact more related to whales than rhinos).
Whether this potential 'GJ 3470 c' exists is not the point. If it is
not impossible, current categories need to be reconsidered.
So, is Pluto a planet, is Phailinsiam, is Jupiter?
What is a planet?
Wait and see.
www.telegraph.co.uk
www.iflscience.com
www.nature.com
www.iflscience.com
theconversation.com
arxiv.org
www.space.com
www.iflscience.com
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