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Tom Mazanec
2017-Dec-18, 02:42 PM
What would be a good word for:
An object large enough to be in hydrostatic equilibrium, but not large enough to generate nuclear fusion?
So I could ask a question like "How many --------s are there in the Milky Way Galaxy?" as opposed to
"How many planets, dwarf planets, exoplanets, rogue planets, really big satellites and really big exosatellites are there in the Milky Way Galaxy?"

Trebuchet
2017-Dec-18, 03:56 PM
"Jupiter"? "Big round things"?

antoniseb
2017-Dec-18, 11:24 PM
Substellar objects constrains the high end. Not sure there is yet a term that gets all forms of the low end.
I assume you have a creative writing need for such a term.

swampyankee
2017-Dec-19, 12:29 AM
What would be a good word for:
An object large enough to be in hydrostatic equilibrium, but not large enough to generate nuclear fusion?
So I could ask a question like "How many --------s are there in the Milky Way Galaxy?" as opposed to
"How many planets, dwarf planets, exoplanets, rogue planets, really big satellites and really big exosatellites are there in the Milky Way Galaxy?"

Well, until the IAU redefined "planet," we could have used that word.

Jens
2017-Dec-19, 01:33 AM
This sounds pretty good: planetary body (https://en.wikipedia.org/wiki/Planetary_body).

grant hutchison
2017-Dec-19, 01:59 AM
Well, until the IAU redefined "planet," we could have used that word.Not for the large natural satellites on Tom's list.
As Jens says, Stern & Levinson's definition of "planetary body" fits Tom's criteria exactly, but I don't think it has been widely adopted as a term of art. Their original 2002 paper, with quite an extensive discussion, is here (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?2002HiA....12..205S&data_type=PDF_H IGH&whole_paper=YES&type=PRINTER&filetype=.pdf) (1MB pdf).

Grant Hutchison

mapguy
2017-Dec-19, 04:09 AM
How about "planetary-mass object", or the shortened form "planemo". From Wiki (https://en.wikipedia.org/wiki/Planet#Planetary-mass_objects): "...massive enough to achieve hydrostatic equilibrium (to be rounded under its own gravity), but not enough to sustain core fusion like a star. By definition, all planets are planetary-mass objects, but the purpose of this term is to refer to objects that do not conform to typical expectations for a planet. These include dwarf planets, which are rounded by their own gravity but not massive enough to clear their own orbit, the larger moons, and free-floating planemos, which may have been ejected from a system (rogue planets) or formed through cloud-collapse rather than accretion (sometimes called sub-brown dwarfs)."

Tom Mazanec
2017-Dec-19, 04:11 AM
And here is a proposed classification of "planetary bodies" by mass, in orders of magnitude:
http://www.astronist.co.uk/astro_ev/_docs/Ashworth_planet_nomenclature.pdf

grant hutchison
2017-Dec-19, 01:32 PM
How about "planetary-mass object", or the shortened form "planemo". From Wiki (https://en.wikipedia.org/wiki/Planet#Planetary-mass_objects): "...massive enough to achieve hydrostatic equilibrium (to be rounded under its own gravity), but not enough to sustain core fusion like a star. By definition, all planets are planetary-mass objects, but the purpose of this term is to refer to objects that do not conform to typical expectations for a planet. These include dwarf planets, which are rounded by their own gravity but not massive enough to clear their own orbit, the larger moons, and free-floating planemos, which may have been ejected from a system (rogue planets) or formed through cloud-collapse rather than accretion (sometimes called sub-brown dwarfs).""Planemo" originated with Gibor Basri, and again fits Tom's criteria. For reasons best known to themselves, he and Mike Brown published a paper in 2006 in which they discussed the problems of planetary nomenclature, and then disagreed with each other about the solution. It's here (https://arxiv.org/abs/astro-ph/0608417). Basri's discussion is at the end.

Grant Hutchison

Tom Mazanec
2017-Dec-21, 06:18 PM
"Planemo" originated with Gibor Basri, and again fits Tom's criteria. For reasons best known to themselves, he and Mike Brown published a paper in 2006 in which they discussed the problems of planetary nomenclature, and then disagreed with each other about the solution. It's here (https://arxiv.org/abs/astro-ph/0608417). Basri's discussion is at the end.

Grant Hutchison

THANKS! I favorited/bookmarked (whichever Apple calls it) that report.