Thread: Are Free-floating Planets 'Planets'?

In 2011, an article on the Nature News site stated:

"They concluded that there could be as many as 400 billion of these wandering planets [planets wandering around the Galaxy's core instead of orbiting host stars], far outnumbering main-sequence stars such as our Sun."

However, if we look in an online dictionary, we read:

Planet:

(1) : any of the large bodies that revolve around the sun in the solar system
(2) : a similar body associated with another star
(Merriam-Webster)

Does this mean we have to extend our definition of the word 'planet'; or do we have to invent a new term for these wandering celestial objects?



Source:
So many lonely planets with no star to guide them : Nature News

I shall repeat my recently posted comments from the Planets thread. They seem apposite.

The thing to keep in mind is that this talk of planets and asteroids an dwarf planets and Kuiper Belt objects and comets and minor planets and satellites is all a reflection on the innate tendency of humans to classify and categorise things. This aids understanding and in a complex world increases survival odds. Nature, on the other hand, does not classify. She produces. She produces a variety of accreted, bombarded, disaggregated, compacted, differentiated bodies, covering a wide spectrum of compositions, origins, shapes, histories, etc. Distinctions are thus, for the most part, arbitrary.

Curiously, I almost added 'free floating planets' to the list of types.

As scientists are researching more about the planets, the theories has also been changing. When the scientists get any conclusion, they expose their research as the theory, which every person accepts. When scientist again discovers something new, they changes the theory again. Like in case of planet, the older theory told that there were 9 planets, but according to new theory 8 planets are considered. So, it can also be possible that after some time definition of ‘planet’ may be change.

So what do we call a solid body 8000 miles in diameter that we find several light years from the nearest star? Is it a planet or something else?

Planet is a word we have invented, and have been using to communicate about certain things we see, it means whatever we agree it should mean. There's not much difference between a moon and a planet, if the Earth orbited Saturn, or if Mars was knocked off orbit and eventually orbited Jupiter, we would use the label "moon" to describe the same object.


Off the top of my head/hat, I would prefer using asteroid for rocks (round or not) without sufficient mass to crumple into a sphere, a planetoid for planets/moons with sufficient mass to crumple into a sphere but without sufficient mass to trigger fusion, and star for planets with sufficient mass to trigger fusion, and black hole for a planet/star with sufficient mass to create a black event horizon. (And use proto-planetoid, proto-star, proto-blackhole for objects that are on the edge of the next label).
But Im not an astronomer.

Originally Posted by The Wiki

A rogue planet — also known as an interstellar planet, nomad planet, free-floating planet or orphan planet — is a planetary-mass objectwhich has either been ejected from its system or was never gravitationally bound to any star, brown dwarf or other such object, and that therefore orbits the galaxy directly.^[1][2][3] Astronomers agree that either way, the definition of planet should depend on its current observable state and not its origin.

And then there's more, this part;

Originally Posted by The Wiki

Larger planetary-mass objects which were not ejected, but have always been free-floating, are thought to have formed in a similar way to stars, and the IAU has proposed that those objects be called sub-brown dwarfs

The word 'planet' initially described 'wanderers' across the heavens, as distinct from stars which, from a mortal terrestrial's point of view, don't move. By that definition, free-floaters would be 'planets'.

Was not the whole reason to de-classify Pluto as not being a planet... because of its irregular shape?

It is too small to be a planet, so now it is a dwarf planet. It is smaller then Earth's moon.

Sure the earth is not completely round either. But (not looked this up),... wasnt their some classification for roundness for space dwelling bodies,... based on the accumalation of mass and such?

What is round anyway?

Cosmic, hell, when I read the question and I thought ...hmmm free floating planet...does that mean a planet not in an orbit? I was right! Dang! *dancing*...ok I am learning!

Originally Posted by Estheria Quintessimo

Was not the whole reason to de-classify Pluto as not being a planet... because of its irregular shape?

It is too small to be a planet, so now it is a dwarf planet. It is smaller then Earth's moon.

Sure the earth is not completely round either. But (not looked this up),... wasnt their some classification for roundness for space dwelling bodies,... based on the accumalation of mass and such?

What is round anyway?

I could answer these questions, but C.G.P. Grey and Henry Reich explain it better than I ever could:
Is Pluto a planet? - YouTube
Round Triangles! - YouTube

I like Pluto....he will always be a planet to me!! *sigh*

Originally Posted by Estheria Quintessimo

Was not the whole reason to de-classify Pluto as not being a planet... because of its irregular shape?

Pluto is more than adequately round. The problem is the other objects discovered in the outer reaches of the solar system: Sedna, Quaoar, Eris, Makemake, etc. These objects are within the Kuiper Belt and the scattered disc. They approach, and in one case, exceed the size of Pluto. Either Pluto needed to be downgraded, or we would have had to declare these objects as planets - and then doubled back and done the same with Ceres at the very least, in the asteroid belt.

Originally Posted by John Galt

Originally Posted by Estheria Quintessimo

Was not the whole reason to de-classify Pluto as not being a planet... because of its irregular shape?

Pluto is more than adequately round. The problem is the other objects discovered in the outer reaches of the solar system: Sedna, Quaoar, Eris, Makemake, etc. These objects are within the Kuiper Belt and the scattered disc. They approach, and in one case, exceed the size of Pluto. Either Pluto needed to be downgraded, or we would have had to declare these objects as planets - and then doubled back and done the same with Ceres at the very least, in the asteroid belt.

PLUTO will always be a planet to me! *GLARE*

Update:

Astronomers have found a little drifting planet, perhaps the very lowest free-floating planet ever found.
The provisionary name is PSO J318.5-22.

From ScienceDaily:

"By regularly monitoring the position of PSO J318.5-22 over two years with the Canada-France-Hawaii Telescope, the team directly measured its distance from Earth. Based on this distance, about 80 light-years, and its motion through space, the team concluded that PSO J318.5-22 belongs to a collection of young stars called the Beta Pictoris moving group that formed about 12 million years ago."

(cf. A strange lonely planet found without a star)

Given the fact that this little planet is not orbiting a star, it is an unique chance for astronomers to learn more about gas giants.

Originally Posted by cogito ergo sum

update:

astronomers have found a little drifting planet, perhaps the very lowest free-floating planet ever found.
The provisionary name is pso j318.5-22.

From sciencedaily:

"by regularly monitoring the position of pso j318.5-22 over two years with the canada-france-hawaii telescope, the team directly measured its distance from earth. Based on this distance, about 80 light-years, and its motion through space, the team concluded that pso j318.5-22 belongs to a collection of young stars called the beta pictoris moving group that formed about 12 million years ago."

(cf. a strange lonely planet found without a star)

given the fact that this little planet is not orbiting a star, it is an unique chance for astronomers to learn more about gas giants.

very cool!

Originally Posted by babe

very cool!

It would be, on account of it not being near a star to warm it up.

It's only 1160 K
PSO J318.5-22 - Wikipedia, the free encyclopedia

(T)	1,160 ± 30/40 K

1160 kelvin = 886.85° Celsius
1160 kelvin = 1628.33° Fahrenheit

I've always thought of a planet as an object that is large enough to be rounded by gravity and who's primary orbit is around a star and it is not itself a star. From that POV this new object is a planet. My take on free planets is that they formed around a star in the usual way and then something happened which forced it out of orbit.

So IMO a failed star should never be called a planet if it meets the size requirements for a brown dwarf category, and if it's in orbit around a primary star that would make it a binary system composed of a star and brown dwarf. If they don't want to call this object a planet, then they need to revise the size requirement for brown dwarfs.

Originally Posted by Bad Robot

I've always thought of a planet as an object that is large enough to be rounded by gravity and who's primary orbit is around a star and it is not itself a star. From that POV this new object is a planet. My take on free planets is that they formed around a star in the usual way and then something happened which forced it out of orbit.

So IMO a failed star should never be called a planet if it meets the size requirements for a brown dwarf category, and if it's in orbit around a primary star that would make it a binary system composed of a star and brown dwarf. If they don't want to call this object a planet, then they need to revise the size requirement for brown dwarfs.

I love when we have meteor nights...it's awesome!

Originally Posted by Harold14370

It's only 1160 K
PSO J318.5-22 - Wikipedia, the free encyclopedia

(T)	1,160 ± 30/40 K

1160 kelvin = 886.85° Celsius
1160 kelvin = 1628.33° Fahrenheit

IF it formed only 12 million years ago, one would expect these kinds of temperatures. Very interesting.

Why do we worry about free floating planets, while we know that our galaxy is freely floating in universe.

All matter in universe is going in same direction no matter free - floating or bound! And we dont know which direction.

So everything is relative. Every motion is relative in this very big frame of reference.
Am I wrong?

Originally Posted by KALSTER

Originally Posted by Harold14370

It's only 1160 K
PSO J318.5-22 - Wikipedia, the free encyclopedia

(T)	1,160 ± 30/40 K

1160 kelvin = 886.85° Celsius
1160 kelvin = 1628.33° Fahrenheit

IF it formed only 12 million years ago, one would expect these kinds of temperatures. Very interesting.

while we know temperature , for sure, of planets so far, so accurately, why cant we get life signatures? Is there any conspiracy of scientists?
(Dont take it serious)

Are free-floating planets 'planets'?

When you name something, you claim ownership over it. When you rename something, you also invalidate the former ownership. There has been a long tradition of people - including scientists - refusing to acknowledge things named and known by others, until renamed. Typically in English, or Latin, or more recently in technical jargon. Then the thing belongs to the namer, it becomes real to him, and he'll defend its existence.

That's why the reclassification of Pluto upset so many people. Who presumes to claim the Solar System? Is it the domain of astronomers, to be obscured by jargon from the common people?

The term "planet" I believe should serve the minds and meanings of common people as well as astronomers. Therefore it shouldn't be hyphenated with qualifiers of a technical nature. Astronomers may quietly divide planets into classes instead, and reclassify to their heart's content which class of planet Pluto belongs in.

To common people a planet worthy of the name is something we might imagine walking on, or if that's impossible at least it's a place we might want to visit. So if it doesn't deserve an orbiting hotel for its own sake, it's not a planet. That's not really useful to astronomers.

Free-floating planets, I'd prefer a less-stilted term. Floaters? Lonelies? Rogues? Milkers?

Originally Posted by sir ir r aj

Why do we worry about free floating planets, while we know that our galaxy is freely floating in universe.

All matter in universe is going in same direction no matter free - floating or bound! And we dont know which direction.

So everything is relative. Every motion is relative in this very big frame of reference.
Am I wrong?

My knowledge of modern physics is not sufficient to confirm or to reject your statements involving relative motion.

Besides, that is not the subject of my thread.
I was simply pointing out that the current definition of the word "planet" does not entail these free-floating planets and I wanted to know if we should invent a new term that groups these objects together or just extend the definition of the word "planet".

Originally Posted by sir ir r aj

while we know temperature , for sure, of planets so far, so accurately, why cant we get life signatures? Is there any conspiracy of scientists? (Dont take it serious)

Scanning for life (on exoplanets) is quite difficult, as it is not entirely clear what we need to detect.

I have already asked this question in another thread:

Originally Posted by river_rat

Right now I don't think we can scan for life, at a bare minimum you would need to be able to do direct spectroscopy of the planet in question to pick up the tell-tail signs in the atmosphere. There were plans a while ago for an array of telescopes in space where one could use interferometry to resolve the exoplanets but I don't think it got very far beyond the planning stage.

Originally Posted by Sealeaf

So what do we call a solid body 8000 miles in diameter that we find several light years from the nearest star? Is it a planet or something else?

I would think its make up would classify it to one or the other.

May I point out that free floating bodies will comprise a large range of sizes. Dwarf planets (say 1000-1500 miles across) are more easily ejected from young stars and their associated planetary systems and so there will be a larger proportion of dwarf planets in the free-floating state. However, the surface temperature of such objects will be so low (no internal source of heat) possibly 10-20K that they are undetectable by any direct methodologies at our disposal. How much mass might be tied up in such free floating bodies and how much of the mass present as 'dark mattter' exists in such a form?

Originally Posted by Astromiles

May I point out that free floating bodies will comprise a large range of sizes. Dwarf planets (say 1000-1500 miles across) are more easily ejected from young stars and their associated planetary systems and so there will be a larger proportion of dwarf planets in the free-floating state. However, the surface temperature of such objects will be so low (no internal source of heat) possibly 10-20K that they are undetectable by any direct methodologies at our disposal. How much mass might be tied up in such free floating bodies and how much of the mass present as 'dark mattter' exists in such a form?

Welcome to the forum

That is a good question, but probably estimates of it have been included in the mass models of the galaxies, when calculating the extra dark matter needed to make galaxies work as they really do.

Asking if "free floating" planets are planets is getting into the politics of it instead of the science. they're planets without a host star. that's it.

I liked Pluto too, however it was "declassified" like stated earlier, due to us finding other bodies like it.

I think the reason was because it could not clear its own orbit. Which means either couldn't clear asteroid belt or it crossed into Neptune's orbit.

[In 2006,] the IAU (International Astronomical Union) ... resolved that planets and other bodies in the Solar System be defined into three distinct categories in the following way —

(1) A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
[1] The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
[2] An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
[3] These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

Well, this is a "short-sighted definition," seeing as how a "planet" must orbit our local star, the Sun.

The IAU is the organization that demoted Pluto — just don't tell babe! On the other hand, Pluto received the distinction of being the archetype of a new class of objects called "Plutoids".

Leave it to scientists to define objects in the solar system thusly —

Those big guys always kick us little folks out of their galaxies!!!

I understand why they removed pluto. However, considering it was due to politics & not wanting to fill text books with all the new bodies we discover...Pluto should of been grandfathered in. That would of been a much better solution

They could of grandfathered pluto.

Originally Posted by GoldenRatio

I understand why they removed pluto. However, considering it was due to politics & not wanting to fill text books with all the new bodies we discover...Pluto should of been grandfathered in. That would of been a much better solution

They could of grandfathered Pluto.

Pluto correlates more with Kuiper Belt objects and has an out of plane orbit (below). Also it is classed as a dwarf planet. (See link below)



Pluto* l* Pluto facts, pictures and information.

yeah. I get that. Im just saying up till a few years ago it was considered a planet. the other kuiper belt objects were not.

Thus, it could of been grandfathered in Grandfather clause - Wikipedia, the free encyclopedia


edit: Also, if you want to get truly technical. Pluto would be defined as a binary dwarf planet with its sister, charon. As the barycenter is not within either bodies mass.

Since planet is derived from the Greek word planetai meaning wanderer, I submit that free floating planets are more entitled to be called planets than those which are restricted to orbiting a star. Free floating planets are the hippies of the universe.

Originally Posted by John Galt

Since planet is derived from the Greek word planetai meaning wanderer, I submit that free floating planets are more entitled to be called planets than those which are restricted to orbiting a star. Free floating planets are the hippies of the universe.

MY KIND OF PLANETS!!!!! THEY MARCH to their OWN orbit!!!

Originally Posted by John Galt

Since planet is derived from the Greek word planetai meaning wanderer, I submit that free floating planets are more entitled to be called planets than those which are restricted to orbiting a star. Free floating planets are the hippies of the universe.

Why do you say they are entitled, is it because of the word free? I don't think you mean the make up of the planet, or do you?

The planets of the solar system move in well defined orbits around the sun. (Or more precisely, the barycentre of the solar system.) They wandered, from an Earth bound perspective, around the sky, unlike the fixed stars. The free floating planets have no such constraint. They are true wanderers, ejected from their birthplace by a larger sibling and condemned to wander the firmament for eons, bereft of the warmth of a parent sun. True wanderers; true planets.

Originally Posted by John Galt

The planets of the solar system move in well defined orbits around the sun. (Or more precisely, the barycentre of the solar system.) They wandered, from an Earth bound perspective, around the sky, unlike the fixed stars. The free floating planets have no such constraint. They are true wanderers, ejected from their birthplace by a larger sibling and condemned to wander the firmament for eons, bereft of the warmth of a parent sun. True wanderers; true planets.

I like your explanation, it reminds me of some patterns we also practice on our planet earth with people. Some children become orphans and wonder off to find a life of their own, others are rejected for one reason or the other. Thanks for your answer.

Yeah beware of those Rogue planets though.