Rogue planets: How wandering bodies in interstellar space ended up on their own

[Admin]

Finding more and more exoplanets to study has, as we might have expected, widened our understanding of what a planet is.

Rogue planets: How wandering bodies in interstellar space ended up on their own : Read more

 

[Mergatroid]

Considering we don't know the origin of all these bodies, nor whether or not they cleared their orbits before being ejected. how can they possibly be called planets?
Wondering bodies at best.
Pluto is more of a planet than any of these.

 

[p3orion]

Don't subtitle an article "How wandering bodies... ended up on their own" if you AREN'T going to tell us "how." There were a couple of lines about 10% of rogues being escapees from their original systems (which seems obvious) but not even any speculation about how the other 90% end up alone, or even why scientists don't believe all of them would have originated in star systems.

How about "Rogue planets: here's how we find them, but not much else" for your title?

 

[p3orion]

Considering we don't know the origin of all these bodies, nor whether or not they cleared their orbits before being ejected. how can they possibly be called planets?
Wondering bodies at best.
Pluto is more of a planet than any of these.

I think the thrust of it is that "planet" is a description more of the mass and structure than of where it's found. (But I agree: Pluto is still a planet. Damn you, Neil Tyson!)

 

[rod]

I note the article states, "However, detecting planets via a single, unique event comes with the disadvantage that we can't ever observe that planet again. We also don't see the planet in context with its surroundings, so we’re missing some vital information. To observe FFPs directly, the best strategy is to catch them while they are young. That means there is still a reasonable amount of heat left over from their formation, so they are at their brightest. In the recent study, researchers did just that."

A previous report on this find is Astronomers uncover largest group of rogue planets yet, https://phys.org/news/2021-12-eso-telescopes-uncover-largest-group.html

Reference paper, A rich population of free-floating planets in the Upper Scorpius young stellar association, https://www.nature.com/articles/s41550-021-01513-x, 22-Dec-2021. "Abstract The nature and origin of free-floating planets (FFPs) are still largely unconstrained because of a lack of large homogeneous samples to enable a statistical analysis of their properties."

My observation. From the abstract cited, "Therefore, ejections due to dynamical instabilities in giant exoplanet systems must be frequent within the first 10 Myr of a system’s life." My note. All these possible rogue planets reported are dated very young in the area near the Sun studied (relative to the age of the Sun, some 4.6 billion years old), perhaps 10 million years old or less. One possible formation mechanism identified is ejection from other planetary systems that formed (obviously very recently relative to the solar system age). This seems to require much catastrophism and violence during protoplanetary disk evolution events postulated to explain the origin of planets. Another question, what is the MMSN protoplanetary disk mass and size needed for large scale, planetary ejections to create a population of rogue planets in the MW? Recent studies on interstellar objects (much smaller than rogue planets) said to pass through our solar system, were ejected from massive disks. Our Sun MMSN is only about 3,330 earth masses or so in many models, I compare modern models with the 1977 MMSN published.

My note, from the phys.org report, "We did not know how many to expect and are excited to have found so many,". This indicates that a specific origin model using gas clouds and protoplanetary disks, did not predict how many rogue planets could be found, so the exact formation of rogue planets is not certain, like heliocentric solar system astronomy. My note. The phys.org report states there could be many more rogue planets that have not been discovered. "There could be several billions of these free-floating giant planets roaming freely in the Milky Way without a host star," Bouy explains." My note. This suggest that billions of rogue planets may exist, free floating in the MW. Do observations like this impose constraints on the postulated evolutionary events in the early solar, protoplanetary disk that Earth is said to evolve from? Example, what constrained our Earth from evolving, *naturally* into a wandering, rogue Earth in the MW?

 

[p3orion]

I note the article states, "However, detecting planets via a single, unique event comes with the disadvantage that we can't ever observe that planet again. We also don't see the planet in context with its surroundings, so we’re missing some vital information. To observe FFPs directly, the best strategy is to catch them while they are young. That means there is still a reasonable amount of heat left over from their formation, so they are at their brightest. In the recent study, researchers did just that."

A previous report on this find is Astronomers uncover largest group of rogue planets yet, https://phys.org/news/2021-12-eso-telescopes-uncover-largest-group.html

Reference paper, A rich population of free-floating planets in the Upper Scorpius young stellar association, https://www.nature.com/articles/s41550-021-01513-x, 22-Dec-2021. "Abstract The nature and origin of free-floating planets (FFPs) are still largely unconstrained because of a lack of large homogeneous samples to enable a statistical analysis of their properties."

My observation. From the abstract cited, "Therefore, ejections due to dynamical instabilities in giant exoplanet systems must be frequent within the first 10 Myr of a system’s life." My note. All these possible rogue planets reported are dated very young in the area near the Sun studied (relative to the age of the Sun, some 4.6 billion years old), perhaps 10 million years old or less. One possible formation mechanism identified is ejection from other planetary systems that formed (obviously very recently relative to the solar system age). This seems to require much catastrophism and violence during protoplanetary disk evolution events postulated to explain the origin of planets. Another question, what is the MMSN protoplanetary disk mass and size needed for large scale, planetary ejections to create a population of rogue planets in the MW? Recent studies on interstellar objects (much smaller than rogue planets) said to pass through our solar system, were ejected from massive disks. Our Sun MMSN is only about 3,330 earth masses or so in many models, I compare modern models with the 1977 MMSN published.

My note, from the phys.org report, "We did not know how many to expect and are excited to have found so many,". This indicates that a specific origin model using gas clouds and protoplanetary disks, did not predict how many rogue planets could be found, so the exact formation of rogue planets is not certain, like heliocentric solar system astronomy. My note. The phys.org report states there could be many more rogue planets that have not been discovered. "There could be several billions of these free-floating giant planets roaming freely in the Milky Way without a host star," Bouy explains." My note. This suggest that billions of rogue planets may exist, free floating in the MW. Do observations like this impose constraints on the postulated evolutionary events in the early solar, protoplanetary disk that Earth is said to evolve from? Example, what constrained our Earth from evolving, *naturally* into a wandering, rogue Earth in the MW?

Thank you for taking the time and effort to expand upon the subject. I was not implying that no mechanism for rogue planets has been identified or postulated, only that the Space.com article had been "dumbed down" to the point of having very little information remaining.

 

[Pogo]

So, if a system can form with one or more stars, and/or a brown dwarf or two, along with any planets and all the other small bodies, I can imagine a small system could form around a gas giant with moons and the other stuff, not enough mass to ignite. Or even imagine a super-earth with a couple of moons and debris; no stars, no dwarves. Mini-systems of all sizes. That’s in addition to any planet-size bodies ejected during formation of all systems.

 

[rod]

So, if a system can form with one or more stars, and/or a brown dwarf or two, along with any planets and all the other small bodies, I can imagine a small system could form around a gas giant with moons and the other stuff, not enough mass to ignite. Or even imagine a super-earth with a couple of moons and debris; no stars, no dwarves. Mini-systems of all sizes. That’s in addition to any planet-size bodies ejected during formation of all systems.

Seems like a very crowded MW with much space junk flying all around, waiting to destroy you when traveling to the stars or buzzing around the Sun here Consider this *creation process* conceived would have to operate over 10 billion years or more, so plenty of free floating junk waiting to create a catastrophe - all around

 

[Helio]

Considering we don't know the origin of all these bodies, nor whether or not they cleared their orbits before being ejected. how can they possibly be called planets?

The planet definition doesn't require an orbit to have been cleared, only that its mass is such that it would clear the orbit over a long period of time. It's Hill's Sphere is the key to tossing.

Here is a great paper that applies astrophysics to determine what mass is required for a given orbit in order to be assured it would clear its orbit. More mass is required with greater distance. The Earth would be a planet up to about 400 AU.

AFAIK, the IAU has not adopted his work, perhaps due to all the fuss.

 

[rod]

The planet definition doesn't require an orbit to have been cleared, only that its mass is such that it would clear the orbit over a long period of time. It's Hill's Sphere is the key to tossing.

Here is a great paper that applies astrophysics to determine what mass is required for a given orbit in order to be assured it would clear its orbit. More mass is required with greater distance. The Earth would be a planet up to about 400 AU.

AFAIK, the IAU has not adopted his work, perhaps due to all the fuss.

If the Earth was at 400 AU Helio, I would not be reading this post of yours now

 

[Helio]

Don't subtitle an article "How wandering bodies... ended up on their own" if you AREN'T going to tell us "how." There were a couple of lines about 10% of rogues being escapees from their original systems (which seems obvious) but not even any speculation about how the other 90% end up alone, or even why scientists don't believe all of them would have originated in star systems.

I wondered the same thing.

I infer that they simply don't have a great explaination for the 90% yet. This is plausible given we are still in the early phase of finding just how many planets and what orbits they have around stars. We are quite limited. 70% of what we are finding is from only those planets that happen to align their orbital plane with Earth.

Perhaps the enigmatic 90% means that a whole lot more planetary activity and quantity are waiting for us around stars. I can't imagine any other scenario for these FFPs than being tossed out far enough where they can "float". [Why am I enjoying their "float" term? Will they sink someday? Are we not floating? I enjoy this sort of poetry.]

 

[Helio]

I think the thrust of it is that "planet" is a description more of the mass and structure than of where it's found. (But I agree: Pluto is still a planet. Damn you, Neil Tyson!)

The funniest think I ever read regarding astronomy was in his "Pluto" book. He said he never dreamed as an astrophysicist that he "would get hate mail for 3rd graders!"

The problem, IMO, is that the Lowell observatory should have asked for a name like Cujo or other negative name. A guide once warned game owners to not name their deer "Big John" or other endearing term else the hunters would be reluctant to hunt.

 

[Helio]

One possible formation mechanism identified is ejection from other planetary systems that formed (obviously very recently relative to the solar system age). This seems to require much catastrophism and violence during protoplanetary disk evolution events postulated to explain the origin of planets."

Yep, I've seen descriptions like "pinball machine" for the early, dynamic formation process.

 

[Helio]

If the Earth was at 400 AU Helio, I would not be reading this post of yours now

That's ok. I would be too cold to write it.

 

[Pogo]

Even with all the debris I think is between the stars, it’ll still be very sparse. Lotsa volume in the galaxy. We’ve sent how many craft through the asteroid belt without a scratch, interstellar is empty in comparison.

 

[billslugg]

For those unfamiliar with the mechanism by which a planet is ejected from a system, it is known as a "three body ejection". My understanding is that three bodies are required, two won't do it. A Solar System analogy would be for a distant comet to enter the inner Solar System at a speed higher than one of the inner planets, come up behind it and gain enough speed to be ejected into outer space. The explanation is that the ejected planet gains speed by sneaking up on the inner planet, passing it, but does not then slow down to its original speed. The reason is that the ejected planet spends sees less gravity on the far side due to its increased speed causing it to spend less time in the planet's gravitational field plus the inner planet turns off to one side further lessening the attraction.

 

[rod]

Even with all the debris I think is between the stars, it’ll still be very sparse. Lotsa volume in the galaxy. We’ve sent how many craft through the asteroid belt without a scratch, interstellar is empty in comparison.

Pogo, it takes only one impact event while traveling in space to make your day

 

[billslugg]

Interstellar space might have on the order of a million atoms per cubic meter, intergalactic space might have one or two atoms per cubic meter. A craft at 10% the speed of light might generate 100 watts per square meter of heat from atomic impact at that speed travelling in our galaxy
.

 

[Pogo]

@rod: I agree, but, fortunately that hasn’t happened yet, so it seems to be not a great issue unlike we see on many science fiction films.

@billslugg: I wonder if a craft could utilize that heat to run a light bulb or two. I imagine that collisions with atoms or molecules might cause erosion with the skin of the craft. Also, as long as that million atoms or so is not one particle.
Tiny particles at orbital velocities make small pits or dents, but at near relativistic velocities, might be more of a problem.

 

[rod]

@rod: I agree, but, fortunately that hasn’t happened yet, so it seems to be not a great issue unlike we see on many science fiction films.

@billslugg: I wonder if a craft could utilize that heat to run a light bulb or two. I imagine that collisions with atoms or molecules might cause erosion with the skin of the craft. Also, as long as that million atoms or so is not one particle.
Tiny particles at orbital velocities make small pits or dents, but at near relativistic velocities, might be more of a problem.

Yes scifi like Passengers movie in 2016 Kinetic energy increases dramatically between Newtonian physics and Relativity as velocities approach c. A 1 gram object traveling at 50.03% c, kinetic energy is 1.03803E+14 joule s^-1, SI units. The faster your starship travels, the more tiny impacts pile up traveling in space - quickly so heat energy will be an issue too as billslugg shows.

 

[Starcrow]

Considering we don't know the origin of all these bodies, nor whether or not they cleared their orbits before being ejected. how can they possibly be called planets?
Wondering bodies at best.
Pluto is more of a planet than any of these.

The problem is not the word "planet" but attaching to it the word "rogue", which is inadequate because it's demeaning, as in "rogue countries" to denote countries that some people dislike. They should be called "lone-wolf planets", "LWPs" or "LWs".

Lone wolves are expelled from the pack and have a hard time surviving because a single wolf can't hunt large prey and has to learn to go after small animals, which are not as easy to catch. Sometimes a lone wolf can go back to the pack, so here the metaphor breaks down, since once a planet is on its own it won't go back, but otherwise it's quite accurate.

Harlow Shapley, who discovered where we are located in the galaxy, came up with the concept of the Brobdingnagian planet, huge planets whose heat caused by gravitational compression allows life to develop on the surface even in absolute darkness, far away from any star. See his essay "Life Among the Dwarfs" in Beyond the Observatory (Charles Scribner's Sons, New York, 1967).

 

[Pogo]

Yeah, rogue planet kinda implies a planet who is lurking about looking for prey, or something. How about non stellar planet, or body because that would not fit the IAU’s third rule of planet referring to clearing its orbital neighborhood of debris

 

[Helio]

How about “Free planets”, like “ free electrons” no longer orbiting nuclei?