"The Mystery of Sedna: The Solar System's Icy ..." Topic

…Oddball World

"In 2004, astronomers announced the discovery of a red, frigid planet-like body at the outskirts of our solar system. Michael E. Brown, the Caltech astronomer who spotted the object (and who would later "kill" Pluto) dubbed it "Sedna", after the Inuit goddess who rules the seas from the bottom of the chilly Arctic Ocean. Sedna quickly spurred imaginations, gracing magazine covers and prompting media speculation of a tenth planet (Pluto was still considered a planet back then.) Brown quelled the planet hype, and Sedna's public limelight gradually faded, but more than decade later, the object remains exceedingly popular with astronomers.

Sedna is a fascinating place. Spherical and close to 1,000 kilometers in diameter, astronomers aren't exactly sure what to make of it. It could be a comet or a dwarf planet. A possible sludge-like coating of hydrocarbons renders it nearly as red as Mars, yet at the same time, it is one of the intrinsically brightest objects in the solar system owing to its slick, reflective composition of methane and water ice.

Sedna's psychedelic look isn't its most intriguing aspect, however. Astronomers are more interested in its orbit. At perihelion -- the point where an orbiting body is closest to the Sun -- Sedna is 76 astronomical units (11.37 billion kilometers) away from the Sun, placing it firmly beyond the orbit of Pluto. But at its farthest distance, it is an astounding 937 astronomical units away! That means that Sedna's orbit, which takes 11,400 years to complete, looks something like this (the purple line is Pluto):…"
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Amicalement
Armand

Interesting.

Unfortunately,this pedant's main takeaway is a renewed wish that journalists would look up what "begging the question" means.

The real "no man's land" zone would be between all gravitational pulling suns, where "debris" hangs out, not inclined to "join" any solar system. Over time, Sol would collect all such debris that happened to enter its gravitational field: "trapped" forever; or until some passing body with greater pull "stole" it away.

As a fellow pedant, I always learn something on these threads.

…,this pedant's main takeaway is a renewed wish that journalists would look up what "begging the question" means.

Begging the question is actually a logical fallacy:

To astronomers, Sedna's whacky orbit begged an obvious question: How did it get out there?

So the journalist is really using "invites" instead of "begged"?

The journalist is first and foremost a writer, aka a "word smith". Well worn phrases are collected, stored, and given back to lend a rhythm to the text.

I guess the use of "begged an obvious question" could be defended on the ground that Sedna, et al. the exoplanets, "got there" by some other means than the "real" planets did; that is the truth that is being begged. So, "how did it get there?" depends on that premise being true: it wasn't there to begin with.

But most of those exoplanets may have originated the same way, not simply have been "snagged" by Sol as they were wandering by too closely.

"How" seems simple to me: gravitational pull on an object that comes close enough to be grabbed by the sun. Pluto's orbit, if I understand this correctly, is circular, but on a canted plane not shared by the "real" planets. Sedna's orbit will eventually stabilize into a circular one as it is pulled in closer. But on what orbital plane relative to Pluto's and the rest? Do most of the exoplanets share a more or less relatively the same orbital plane? Or are most them all over the place? I don't know how much orbital plane variability exists. This is a new question to me…………..

I just listened to the audiobook version of Mike browns book on finding Sedna and killing Pluto. It is very very good. Highly recommended.

Yes, AGW that makes sense. However, H von S is correct in that "begging the question" actually means something and it is other than what the writer was trying to express.

As for the orbits, all planets revolve around the Sun in elliptical orbits that are close to circular. Here is a nice overview:

nineplanets.org/overview.html

This was discovered in the early 1600's by Kepler and reconfirmed by Newton later in the century. The cool thing is it explains why the velocity of the orbiting body speeds up closest to the foci of the ellipse. So for any equal unit of time, the surface area of the segment of the ellipse traveled by the orbiting body is equal. Still a great mathematical intuition on Kepler's part. Now we would say that the Sun distorts time-space and this accelerates the body as it comes closer to the gravity well.

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… orbits that are close to circular.

You don't surprise me, since you are in a pedantic mindset. But to be agreeably pedantic, I want to point out that nothing "circular" in the universe, in existence, is a "perfect circle". Using fractals you can always reduce the "perfect" into something still not quite perfect, indefinitely…………..

logical fallacy

Yep,petitio principii. "Invited","raised",or "prompted" would be correct.

But the misuse is now so widespread that I wouldn't be surprised to see some dictionaries allowing it.

You don't surprise me, since you are in a pedantic mindset.

I admitted that. I simply wanted to show that this knowledge is 400 years old.

But most of those exoplanets may have originated the same way, not simply have been "snagged" by Sol as they were wandering by too closely.

"How" seems simple to me: gravitational pull on an object that comes close enough to be grabbed by the sun. circular one as it is pulled in closer. But on what orbital plane…….

Well apparently, it's not that simple.

Firstly, you are using the term "exoplanet" incorrectly. Sedna is not an exoplanet.

Secondly, it is most likely that Sedna, Pluto and the rest of the gang in the Kuiper Belt formed from the same accretion disk, or protoplanetry disk that made the other planets, including the Earth.