Pluto's interactions with the solar wind are unique, study finds

May 4, 2016, American Geophysical Union
Using data from an instrument aboard the New Horizons spacecraft gathered on its Pluto flyby in July 2015, scientists have observed the material coming off of Pluto and seen how it interacts with the solar wind. This figure shows the size scale of Pluto’s interaction with the solar wind derived from the data. The bow shock is indicated by the extension of the locations where the study’s authors measured the light, solar wind ions to be about 20 percent slowed down from the upstream solar wind speed. The Plutopause (purple) is a finite-sized boundary layer ~0.9 Pluto radii thick at the nose and separates the solar wind (blue) from the heavy ion tail (red). Even though the heavy ion tail extends back more than 100 Pluto radii at the time of the New Horizons flyby, the upstream interaction is very compact and the bow shock is almost compressed onto the obstacle. Credit: American Geophysical Union. 

Pluto has some characteristics less like that of a comet and more like much larger planets, according to an analysis of Pluto's unique interaction with the solar wind, scientists say.

Using data from an instrument aboard the New Horizons spacecraft gathered on its Pluto flyby in July 2015, scientists have observed the material coming off of Pluto and seen how it interacts with the solar wind, and found it completely new – and unexpected.

"This is a type of interaction we've never seen before anywhere in our solar system," said David J. McComas, lead author of the new study published today in the Journal of Geophysical ResearchSpace Physics, a publication of the American Geophysical Union.

McComas, professor in Princeton University's Department of Astrophysical Sciences and vice president for the Princeton Plasma Physics Laboratory, leads the Solar Wind Around Pluto (SWAP) instrument aboard New Horizons; he also led development of SWAP when he was at the Southwest Research Institute (SwRI) in Texas. The research was funded as a part of the New Horizons project by NASA.

Space physicists say that they now have a treasure trove of information about how Pluto's atmosphere interacts with the solar wind. Solar wind is the plasma, or charged particles, that spews off from the sun into the solar system at a supersonic 400 kilometers per second (1 million miles per hour), bathing planets, asteroids, comets and interplanetary space in a soup of mostly electrons and protons.

"The results are astonishing. We were fascinated and surprised" by the findings, McComas said.

Previously, most researchers thought that Pluto was characterized more like a comet, which has a large region of gentle slowing of the solar wind, as opposed to the abrupt diversion solar wind encounters at a planet like Mars or Venus. Instead, like a car that's part gas- and part battery-powered, Pluto is a hybrid, the researchers say.

"This is an intermediate interaction, a completely new type. It's not comet-like, and it's not planet-like. It's in-between," McComas said. "We've now visited all nine of the classical planets and examined all their solar wind interactions, and we've never seen anything like this."

Schematic diagram of Pluto’s interaction with the solar wind as inferred from SWAP observations along the trajectory of the New Horizons flyby. New Horizons crossed the Sun-Pluto line from the dawn/southern portion of the tail (dashed portion of trajectory) into the dusk/northern (solid portion of the trajectory in the cutaway) at ~44 Pluto radii down tail. Portions of the trajectory inside the heavy ion tail behind Pluto are indicated in red and light ion sheath that surrounds the tail are in blue. The bow shock observed near Pluto has dissipated into just a bow wave by the distance back that New Horizons exited through it. Credit: American Geophysical Union.
"These results speak to the power of exploration. Once again we've gone to a new kind of place and found ourselves discovering entirely new kinds of expressions in nature," said Alan Stern, New Horizons principal investigator at the Southwest Research Institute. "Many people were surprised by Pluto's complex geology and atmosphere. This paper shows there's even more that's surprising there, including its atmosphere-solar wind interaction."

Pluto continues to confound. Since it's so far from the sun – an average of about 5.9 billion kilometers (3.7 billion miles) – and because it's so small, scientists thought Pluto's gravity would not be strong enough to hold in its extended atmosphere. But, "Pluto's gravity clearly is enough to keep material sufficiently confined," McComas said.

Further, the scientists found that very little of Pluto's atmosphere is comprised of neutral particles converted to electrically charged ions and swept out into space.

"This is backwards for many other planets, where the neutral particles stay relatively close to the planet," said Michael Liemohn, a University of Michigan astrophysicist and Editor-in-Chief of JGR-Space Physics, who was not involved with the research but who helped edit the paper. "An ion particle becomes influenced by the electric and magnetic forces present in the solar system, which can be a very efficient acceleration processes. But at Pluto, McComas et al found that only a wisp of atmosphere leaves the planet as ions."

The researchers were able to separate the heavy ions of methane, the main gas escaping from Pluto's atmosphere, from the light ions of hydrogen that come from the sun using the SWAP instrument.

Among their Pluto findings:

  • Like Earth, Pluto has a long ion tail, that extends downwind at least a distance of about 100 Pluto radii (119,000 kilometers (73,800 miles), almost three times the circumference of Earth), loaded with heavy ions from the atmosphere and with "considerable structure;"
  • Pluto's obstruction of the solar wind upwind of the planet is smaller than had been thought. The solar wind isn't blocked until about the distance of a couple planetary radii (2,968 kilometers (1,844 miles), about the distance between Chicago and Los Angeles);
  • Pluto has a very thin "Plutopause" – or boundary of Pluto's tail of heavy ions and the sheath of the shocked solar wind that presents an obstacle to its flow.

The scientists write: "Pluto interaction with the solar wind appears to be a hybrid with the bow shock generated by mass-loading like at a comet, but the obstacle to the solar wind flow – the Plutopause – sustained by atmospheric thermal pressure as at Venus and Mars."

Heather Elliott, astrophysicist at Southwest Research Institute and co-author on the paper, said that the study provides interesting comparisons. "Comparing the solar wind-Pluto interaction to the solar wind-interaction for other planets and bodies is interesting because the physical conditions are different for each, and the dominant physical processes depend on those conditions," Elliott said.

What is significant, McComas said, is the range of diversity that bodies in the solar system have with the solar wind. Further, the findings offer clues to the magnetized plasmas that one might find around other stars. "The range of interaction with the solar wind is quite diverse, and this gives some comparison to help us better understand the connections in and beyond our solar system," McComas said.

The scientists conclude: "The SWAP data will … be reanalyzed … for many years to come as the community collectively grapples with Pluto's unique interaction – one that is unlike that at any other body in the ."

New Horizons is the first mission in NASA's New Frontiers program, managed by the agency's Marshall Space Flight Center in Huntsville, Ala. The Johns Hopkins University Applied Physics Laboratory designed, built, and operates the New Horizons spacecraft and manages the mission under Principal Investigator Dr. Alan Stern's direction for NASA's Science Mission Directorate. SwRI leads the science mission, payload operations, and encounter science planning. The NASA Heliophysics program also supported the analysis of these observations.

Explore further: Multitasking New Horizons observed solar wind changes on journey to Pluto

More information: "Pluto's Interaction with the Solar Wind," D. J. McComas et al. , 2016, Journal of Geophysical Research - Space Physics, … 016JA022599/abstract

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Display comments: newest first

1.7 / 5 (23) May 04, 2016
Surprise, surprise, surprise... Measurements don't agree with theory, just like every other aspect of space plasmas starting from day one of man's endeavours of space exploration.
4.7 / 5 (25) May 04, 2016
Surprise surprise surprise, an Acolyte misunderstands how science and discovery works.
1.7 / 5 (23) May 05, 2016
Surprise surprise surprise, an Acolyte misunderstands how science and discovery works.

Science rests on empty stories and fairy tales and it is not surprising that we have surprise, surprise ...
3.5 / 5 (19) May 05, 2016
"Plutopause". Hmmm. Shouldn't that be "Pluto Paws"?

Re: the trolls PO have doubled down on their promoting trolling. Last week we saw them delete an account for the generic statement that someone would love the chance to dance on the trolls' grave, yet trolls get seldom get accounts deleted for saying racist, personally threatening, slanderous statements, and just pure misinformation. Can anyone remember one having an account deleted for just one deleted post? It certainly wasn't up to the level of what the trolls do every day with impunity from the mods, so one can only conclude that they're running a little troll farm. I say we take serious discussion to the forum, which is moderated, and teach them which side their bread is buttered on by posting no comments on the articles. Let it be total troll spew and pretty clear what an embarrassment it all is.
Captain Stumpy
4 / 5 (21) May 05, 2016
Can anyone remember one having an account deleted for just one deleted post?
yep. for a death threat
although i think the account you're referring to likely got deleted for stating PO was pandering to the trolls... perhaps you contact the site and complain more about the trolls, liars, idiots and request moderation?
I've submitted a plan that would be minimal set-up cost (just adjusting some profiles for temp bans) and free moderation from the existing profiles, with a list of the best candidates known to be degree holing professionals (- not like gkam)

push for it



EU sewer-rat @cantgetitright gets it wrong
funnier still, the lead author and contact VP's the Princeton Plasma Physics Lab" title="http://" rel="nofollow" target="_blank">http://www.pppl.g...boratory

IOW- that study is chock full of folk who specialise in nothing but plasma physics
2.9 / 5 (19) May 05, 2016
"a list of the best candidates known to be degree holing professionals (- not like gkam)"
Let's compare university degrees, shall we? What university degree do you "hole"?

How about actual experience?

You first. You saw mine already, most of it. There is still a surprise or two for you to find, but that is most of it.

Give up your need to "get even" with those of us who proved you to be just a nasty guy with sensitive feelings, so we can discuss the science.
Captain Stumpy
2.8 / 5 (20) May 05, 2016
going to reply once
so we can discuss the science
this requires evidence, links and references which you have yet to be able to provide *supporting your arguments*
your arguments tend to be predominantly anecdotal and from authority

when you claim to have a degree, therefore you *must* be correct despite the evidence proving you're wrong or lying then it stops being about science and becomes about a pathological need for attention (AKA- Trolling) and disruption of content with narcissistic promotion of self (sociopathic/psychopathic)

thus you demonstrate Dunning-Kruger, not science
See links below for evidence

just to link a FEW
so my degree's are not relevant because i'm not making the argument from authority

reported for spamming/baiting/trolling per our agreement
3.2 / 5 (20) May 05, 2016

Without a degree or experience in these fields, your ideas have no merit, according to your own analysis.

- Reported for improperly using the report function.
3.2 / 5 (20) May 05, 2016
BTW, Rumpy, look up how to use the apostrophe.

2 / 5 (16) May 05, 2016

Without a degree or experience in these fields, your ideas have no merit, according to your own analysis.

- Reported for improperly using the report function.
- gkam
LOL I find it interesting and humorous that Cap'n StumpRump regards you (and others) as a "troll", while at every opportunity the Rump Captain can't seem to help herself in paying an enormous amount of attention to you, no matter in which thread you have made comments.
There must be a psychological description for such an action and motivation on Cap'n Rump's part of her/your relationship.

Dunning-Kruger may also apply to Cap'n Rumpy's obsessive demands for substantiation/evidence as though she is a college professor conducting a test/examination where "trolls" will be given grades A+ to F for Fail.
And yet, Rumpy can ONLY quote from Wiki and other Search sources while offering links to what she has learned so that "trolls" can also learn from the same source(s). You are feeding Rumpy's huge ego, IMO
2 / 5 (16) May 05, 2016
It appears that Cap'n Rumpy's high-flying ego soars only when she has found someone to belittle, curse out, and "dress-down" for failing to pass her "tests".
But I also notice that you, gkam, are encouraging Cap'n Rumpy's trolling habits while she pretends only to care about the science. Rumpy, as well as Otto and Ira are trolling YOU, benni, bschott and antigoracle, mainly. They can't abide your presence in these forums. You give them discomfort with all your talk of having degrees and various accomplishments.

There seems to be no solution to this silly nonsense.
1.3 / 5 (12) May 05, 2016

"Rings on Pluto? Quote from the article in 2013: Until some other opportunity, maybe already in the spring of 2015, when the New Horizons mission will have reached Pluto, to convince us that it does not have rings. The calculations are clear: slow speed of rotation around its own axis, small mass, and even though there is very favorable low temperature, there are no rings. but, it is needed to point out that the values are contiguous, which is demonstrated by the mass of its satellites. Related to their home planet, they are in terms of mass by far beyond the average of the Sun and other planets 8. " Comentar to: etc., etc.
2 / 5 (21) May 05, 2016
He's a troll, full stop. I thought we weren't supposed to blithely feed the trolls. I say you tell his ilk- the kind that have zero interest in the topics, just want to spew "science is a fairy story!"- to get off in the rudest possible terms, or say nothing. Gratuitously feeding them like that, imho, is as bad as the post itself.

You're the biggest disruptive troll posting at,... with your multitude of troll-rating accounts...

..........NiteSkyGerl, antigoresockpuppet, fckthierreyhenry, BongThePuffin, john berry_hobbes, maloderousmiscreant, YoureAPeanut, GoshURStupid, tooty, jim_xanara, AGreatWhopper, chileastro..........

all mass troll-rating my posts irrespective of content going back 6 pages, as in the following thread with factual posts.........

This is not a scientific journal. Use the ignore option, or stop interjecting your off-topic disruptions yourself into the thread.
4.2 / 5 (15) May 05, 2016
+bschott I think the upshot of why Dark Matter doesn't clump together is because in order to be clumped you have to be stationary. In order to make a moving particle stationary it must lose energy. Dark Matter predominately (only?) interacts gravitationally and so there are no dispersive forces at work to slow them down. This is unlike normal (electromagneticly interacting) matter particles where there are dispersive forces like friction slowing the particles down.

Instead these Dark Matter particles would just fly towards eachother due to the mutual attraction and then just fly off into the distance with all their energy in check.

Edit: this is an invigorating read!
1.5 / 5 (16) May 06, 2016
Hi Phys1, bschott, everyone. :)

Phys1, what you just pointed out is what I also pointed out long ago. That is why 'exotic' (ie, non-electromagnetically interactive) DM is NOT logically/physically tenable hypothesis for (observed) galactic Rotation Curves and (alleged) 'exotic DM' 'clumps/toruses'. Add the alleged cosmological 'expansion' claimed, and 'exotic' DM should be totally dispersed in equilibrium by inertial/kinetic SEPARATION into a diffuse 'gas' everywhere with no 'lumps' in it (for the very reasons you just iterated; and which I also have been pointing out for years). Add also recent/increasing discoveries of ORDINARY erstwhile 'dark' matter in many forms, plus my pointing out the NON-Keplerian orbits within spiral galaxies being still MIS-interpreted as 'needing exotic DM', and you can see just how UN-tenable all that 'exotic' DM interpretations/claims/excuses are in reality.

How long do you think it will be before mainstream 'papers/articles' self-correct? :)
1.5 / 5 (17) May 07, 2016
Hi Phys1. :)

Don't sell yourself short, mate; your initial statement was spot on. If you read your wiki reference closely you will note that no actual 'mechanism' is identified or explained, only 'labeled' as 'virial'' but without logical/physical basis for how and why such initial perturbations should not disperse due to cosmological expansion and lack of e-m interactions which would slow their initial inertial speeds (just as you stated).

So your point/statement remains unchallenged. That wiki merely makes a vague claim of "virialisation" but does not actually explain how that comes about and persists in the face of expansion/dispersion as you earlier observed. Moreover, the Cold DM hypothesis has recently been challenged by the Hot DM hypothesis after simulations (by one of the 'fathers' of the Cold DM hypothesis) which show similar cosmological distribution 'results'. But in any case, no 'exotic' DM is tenable (for reasons you and I together have pointed out above). :)
1.4 / 5 (11) May 07, 2016
Gravity does not impart inertia on matter.

How does matter that only reacts gravitationally gain inertia in the first place?

Gotta go lads, looking forward to picking back up tomorrow.

Matter reacting to gravity, being pulled towards it, gains speed, more inertia.So gravity does add inertia to matter. Matter has it's own attraction to gravity as well. There just needs to be enough gravity in the first place.

3.4 / 5 (17) May 10, 2016

cantdrive85 1.4 /5 (18) May 04, 2016
Surprise, surprise, surprise...

that the most brainless comment
On this thread
Is from CD85!
Captain Stumpy
4.2 / 5 (15) May 11, 2016
... flattening at the poles?
... talking about the sun...not earth
see first paragraph below, and then read under the header "Our flatter sun"

theoretical (as of yet unobserved) particle
*the particle* is unobserved
it's *effects* are observed which is where the whole DM theory comes from (and why we're testing various methods for specific identification of said particle with falsifiable predictions)
I predict that before either of us dies, the current version of the standard model will, along with all of its "phantom" components which currently only manifest as math holding it together as a theory
did you leave some important stuff out of that post?
you predict it will what?

and if your talking eu, remember eu is already falsified
this is like the FDA/mag-cancer conversation we had - how can you support something that has no evidence but anecdote?
1.9 / 5 (13) May 11, 2016
Why, I am talking about the sun.
"the Sun is a near-perfect sphere with an oblateness estimated at about 9 millionths"
Oblateness means flattening.

Well, both you and wiki are out of date and as usual, wrong.

Odd that a physicist would rely so heavily on wiki, more of an arm chair "physicist" I suppose.
1.7 / 5 (12) May 11, 2016
remember eu is already falsified

Ummmm, not even close. Please link the peer-reviewed paper which specifically falsifies the EU theory. No pseudoscience blogs from "Pith ball" Timmy Thompson or some other acolyte of the dark sciences. Only peer-reviewed papers which specifically addresses claims made by EU. With all your constant claims this should be easy enough even for you.

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