
85 Years After Pluto’s Discovery, New Horizons Spots Small Moons Orbiting Pluto - robin_reala
http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150218
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kartikkumar
Pluto is ridiculously cool. Small body research is at the forefront of getting
a handle on the conditions of the early Solar System. Between discoveries made
by the Rosetta mission [1], Dawn's visit to Vesta and Ceres [2], and the
incredible discovery of rings around Chariklo [3], we are really in a golden
age at the moment.

New Horizons has a lot more in store, not in the least because we know that
there are at least two other moons in the system: Styx [4] and Kerberos [5]
(discovered by my advisor Mark Showalter [6]). There's been a concerted effort
to search for rings around Pluto too, not in the least to be able to assess
the safe passage of New Horizons through the system.

All I can say is don't blink, you're not gonna wanna miss this!

[1] [http://rosetta.esa.int/](http://rosetta.esa.int/)

[2] [http://dawn.jpl.nasa.gov/](http://dawn.jpl.nasa.gov/)

[3]
[http://en.wikipedia.org/wiki/Rings_of_Chariklo](http://en.wikipedia.org/wiki/Rings_of_Chariklo)

[4]
[http://en.wikipedia.org/wiki/Styx_(moon)](http://en.wikipedia.org/wiki/Styx_\(moon\))

[5]
[http://en.wikipedia.org/wiki/Kerberos_(moon)](http://en.wikipedia.org/wiki/Kerberos_\(moon\))

[6] [http://www.seti.org/users/mark-showalter](http://www.seti.org/users/mark-
showalter)

~~~
swamp40
Mark Showalter is like the _Moon Whisperer_.

How can any single person these days discover six moons and three planetary
rings?

~~~
kartikkumar
You've gotta see him in action; he gives great talks. Here's a recording of
his SETI talk on the discovery of Styx and Kerberos:
[https://www.youtube.com/watch?v=u6t51YPOuSA](https://www.youtube.com/watch?v=u6t51YPOuSA)
(I worked on Uranus' moon Mab, which is mentioned at the start of the talk).

If you get the chance to see him live, I'd definitely recommend it.
Unfortunately, he's very busy, so even during my PhD I haven't had many
chances to sit down with him.

The coolest thing to me is that Mark is a dynamicist actually, but has such a
deep understanding of instrumentation and image processing that he can attack
new discoveries from both sides. Good example of why it serves to have many
tools in your toolbox.

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iamwil
Oh man, it finally made it. I remember working on the ground telemetry bit for
New Horizons about 11 years ago (has it been that long?). The C++ code base
was hard to understand, and I'm sure I didn't make it any better as a junior
developer.

I worked on the part that said, "Hey, are you still there?", and listened for
"Yeah, I'm still alive." That was my small contribution.

It was one of the few groups at APL at that time that was actually using
source control. (hurray!) Everyone else was doing something akin to copying
file folders on a shared drive. I was even on a code base that had comment
annotations of the person that changed the line. I think APL has adopted
source control lab-wide now, after some hard lobbying by software devs there.

Ahh, good times.

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32faction
My understanding was Pluto could not be a "planet" because it was not a part
of the formation of the original solar system due to it being located beyond
the frost line boundary [1] which separates terrestrial planets from gas
giants.

Basically, anything within the frost line boundary is close enough to the
protosun that things like solid water, CO2, et al. melt, allowing for
accretion of solid matter and eventually rocky (terrestrial planets). Anything
beyond the frost line, and these solid materials freeze up then accrete, and
then collect gas from the protosolar accretion disk, forming gas giants.

It's entirely possible Pluto could've been a part of the original solar system
but somehow wasn't massive enough to collect gas, or it was a captured object
not present during the formation of the solar system.

Either way, I'm sure New Horizons will discover more.

In my opinion, the IAU was correct in downgrading Pluto to a dwarf planet.
Scientific observation and study should not be dictated by social tradition.

[1]
[http://en.wikipedia.org/wiki/Frost_line_%28astrophysics%29](http://en.wikipedia.org/wiki/Frost_line_%28astrophysics%29)

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smackfu
It's interesting that they are doing research using images that are going to
be obsoleted very soon as the probe gets closer.

~~~
semaphoreP
I think these images help them figure out what's interesting to study as the
probe gets closer. It's going to zoom by, so they need to know beforehand what
to look at.

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pslam
There's another object near the left edge of the video, moving from top to
bottom. Does anyone know what that is?

Its movement per frame seems too consistent and predictable to be an artifact
(noise) of the camera.

~~~
flashman
That's very interesting. It's not moving with the background stars. However it
could still be a camera artifact - see how there's a 'trail' behind Pluto's
disc? In frames 4-7, the object you've identified is in the same position
relative to the trail (off to the right if you are following a line outwards
from Pluto along the trail).

I made an image to show what I mean. See frames 4-7; it's not an exact match
but maybe it's a clue:
[http://i.imgur.com/TADflVd.jpg](http://i.imgur.com/TADflVd.jpg)

~~~
pslam
Thanks for making that!

I hadn't considered the rotation, because as you point out, it doesn't exactly
match up. It's gaining distance from the center of image as it moves.

It could still be some kind of internal reflection artifact (even dust?) which
varies in distance slightly, I guess. I'm pretty sure the team looking at
these images would have gone over every object in depth, so it's unlikely I've
spotted something they haven't :)

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cellover
Very interesting! I also highly recommend the following video just published
by Silicon Valley Astronomy Lectures:

Pluto on the Horizon: Anticipating our First Encounter with the Double Planet

[https://www.youtube.com/watch?v=KfODJpfS0fo&feature=em-
subsc...](https://www.youtube.com/watch?v=KfODJpfS0fo&feature=em-subscription-
upload)

[Edit] - Adde video title

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unreal37
Moons? It's a planet after all! Reinstate! Reinstate!

~~~
kartikkumar
That's not what the IAU classification is based on [1]. There are dynamical
reasons to argue for the fact that a planet has to have cleared it's orbit.
Pluto fails in this regard. A lot of people mistake the reclassification of
Pluto as folly, when there are fundamental reasons that underpin the current
definition of a planet. This has evolved as we've come to understand the
dynamical processes that shape the Solar System.

[1]
[http://en.wikipedia.org/wiki/IAU_definition_of_planet](http://en.wikipedia.org/wiki/IAU_definition_of_planet)

~~~
beeworker
> There are dynamical reasons to argue for the fact that a planet has to have
> cleared it's orbit

Maybe so, but as the wiki article points out in its criticism section, this
excludes Earth, Mars, Jupiter, and Neptune from being planets.

I don't think it's so much folly as much as a waste of everyone's time.
"Planet" isn't a natural thing like the speed of light, if astrophysicists
want to be more specific about which orbiting bodies they're talking about,
which "dynamical processes" they're talking about, they should come up with a
new term instead of dragging literally everyone (including the children!) into
an argument over definitions. It's like a scientist insisting that "sound" can
only refer to this vague thing a brain experiences, and it can't refer to
generic vibrations in the air, but some people are still on the fence about
whether it can refer to vibrations in water.

~~~
pash
I don't believe the International Astronomical Union has offered an opinion
about the Webster's definition of the word, or about how you and your six
year-old may use "planet" in ordinary language.

The IAU's definition is a scientific definition, one that pertains to usage
among astronomers. Insisting that astronomers make up another word is silly
for all the same reasons that (as you pointed out) it would be silly for
astronomers to tell us how to use one of our everyday, non-technical words.
The same sequence of characters or phonemes can have slightly different
meanings in different contexts.

~~~
lmm
But the IAU definition makes no sense for astronomical use, _particularly_ as
we get better at finding extrasolar plane^H^Horbital bodies. We're going to
have hundreds of repeats of Ceres/Vesta/Pluto - bodies that we discover,
consider to be planets, and then only much later with finer techniques
discover that there were other bodies in the same orbit. That's not good for
science.

~~~
FiatLuxDave
Upvoted, as this is an excellent point. The IAU definition makes serious
presumptions about our level of knowledge. Could the IAU definition be used at
the time of Pluto's discovery? If not, what does that say about using this
definition for future discoveries?

Note that I'm not saying that I think that dwarf planets should be categorized
as planets (there are too many), but that the definition shouldn't depend upon
us having complete knowledge of every object in a newly discovered potential
planet's neighborhood.

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skruvmejsel
A pity they didn't name the two moons Chip and Dale.

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nsxwolf
Dwarf moons for a dwarf planet? This reclassification is getting harder to
justify.

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cjensen
Many asteroids have moons [1]. This has no effect on the reclassification.

[1] [http://en.wikipedia.org/wiki/Minor-
planet_moon](http://en.wikipedia.org/wiki/Minor-planet_moon)

~~~
thisisandyok
Fascinating. Thanks for the link

