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The Sun's 10th Planet... Sedna?
dsanfte writes "While NASA remains intentionally vague, promising only a news conference Monday, The Australian has the details. The new planet, dubbed Sedna after the Inuit goddess of the sea, is 3 billion km further from the sun than Pluto, and is slightly smaller at 2000km in diameter. This discovery has apparently reignited the debate as to how big a solar object must be in order to qualify as a 'planet', but it is significant nonetheless."
Pluto is 2300 km diameter, ranges from 4.3 to 7.4 billion km from the sun.
i stics.html
http://www.windows.ucar.edu/tour/link=/pluto/stat
wasn't there something quite a while back about "trans-neptonian objects" not qualifying as planets, but that the organization that determines such things stated that pluto/charon would get included, but anything else was out?
Actually, they switched back in 1999; Pluto is again further away than Neptune.
And what about all those M-V-E-M-J-S-U-N-P mnemonics we learned. Those already had to be retrofitted to become M-V-E-M-J-S-U-P-N, now they need to extend to M-V-E-M-J-S-U-P-N-S.
Correction - Neptune was farther from Pluto from January 21, 1979 to Feb. 11, 1999 but at this time Pluto is farther from the sun than Neptune.
Of course, there's debate as to whether Pluto-Charon is a planet with a moon, or a double planet...
- Thomas;
___ This sig is in boldface to emphasize its importance!
"FAR" is a very vague thing in space.
Yes, its near, but its small and its cold. So its only to detect if you are looking EXACTLY at it.
A blue giant a million light years away is MUCH easier to spot that that pile of cold rock.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
The binoculars also limit or eliminate local vision while in use, obscuring the approach of your spouse/mother and a disapproving hand. . .:)
You are not the customer.
It was only something like 1,400 klicks across, if memory serves. So this new find does at least have the distinction of being substantially larger.
Bush: He's Liberal in all the wrong ways.
Janus is already a moon of Saturn, IIRC.
You are not the customer.
Quaoar (though some claim it's too small for a planet...)
Alf predicted them both!
Anagram("United States of America") == "Dine out, taste a Mac, fries"
Sedna is over 4 times the size (volume) of Quaoar.
Whether it's a planet is a silly argument, but even so, "we already have Quaoar" is really irrelevant.
The precession of Mercury's orbit is explained by the general theory of relativity, not the special theory. The special theory explains the results of the Michelson-Morley experiment.
Vesta has already been used.
Don't go to a brothel if you want to buy broth
Comets are snowballs; asteroids are rocks. Oversimplification, but you get the idea.
If all this should have a reason, we would be the last to know.
That would be Prometheus, but thank you for playing.
Philip Sandifer's academic website
Hockey was invented somewhere in Europe or European North America in the 19th century. Lacrosse was invented by Indians near the St. Lawrence and is played on grass rather than snow, so I doubt the Inuit were involved.
Inuit inventions include snowshoes, toboggans, dogsleds, kayaks, toggle harpoons, and various other tools for hunting and travelling in the North as well as snow and ice civil engineering techniques. Pretty impressive, I'd say, for a culture with almost no wood, rock, or metal. They've probably contributed as much as any other non-Eurasian colonialised culture, and they make some really cool art.
Clyde Tombaugh who discovered Pluto performed an exhaustive search for Planet X for several decades. From his results he concluded that there were no undiscovered Jupiter-sized bodies within 470AU of the Sun, and no Neptune-sized objects with 210AU. (Pluto is never more than 50AU from the Sun).
The Oort Cloud is believed to have been populated by planetismals thrown out of the early inner part of the Solar System by the formation of Uranus and Neptune. They would have slungshot smaller bodies into the outer darkness into orbits that match the hypothetical orbits in the Oort Cloud. They would not have been able to shunt anything larger out that far - at least not without disrupting their own formation.
A further problem is that planet formation models run into trouble this far out. Distances between the planetismals that made up the proto-planets would have been so great, and relative velocities so small that its hard to see how they would ever have collided to built up a bigger planet.
Best wishes,
Mike.
IMO, Pluto should [shouldn't?] be labeled an asteroid since it's smaller than even our own moon [wikipedia.org].
An interesting point, though to be fair, its an arbitrary cutoff. There are moons elswhere in our solar system larger than Mercury, which is indisputably a planet, for example. Also its worth pointing out that our moon is large enough that it and Earth are sometimes called a double planet. Consider this, Luna does not orbit Earth as near the equator as is usual among most other moons. Also, peculiar to all 138 known moons with the exception of Charon, it possesses an orbit where the effect of the Sun's gravity is greater than that of Earth's. Without their host planets, they would float off, wheareas the moon would continue orbiting the sun quite contently.I think ultimately the question is whether there is a single continuous "initial mass function" of isolated objects or not. The best idea as to how stars acquire their initial mass is that turbulence in the interstellar medium, which exists on all scales, establishes a power-law distribution of initial masses. Every once in a while, you get a very strong shock which passes by inside a giant molecular cloud and forces the collapse of a large region which then goes on to form a massive star. But more typically, you form stars more like our sun. And just as rare as massive collapses are very small mass ones which go on to form isolated brown dwarfs and free-floating planets. If this model holds up to be true, then we are all mincing words in our definitions of isolated systems, since they are all manifestations of the same universal formation process.
However, to avoid the difficult question of formation mechanisms, an IAU working group of some of the most respected people in the field established a working definition to define by fiat what it means to be a brown dwarf, and a planet. Extrasolar "planets" are those objects orbiting a star which are beneath the deteurium-burning limit -- regardless of how they are formed. "Brown dwarfs" are defined to be those which burn deuterium but not lithium, and "sub-brown dwarfs" (NOT free-floating planets!) are defined to be those isolated objects which do not burn deuterium. Even the working group itself admitted that this definition was not satisfying to a single member of the group, and so it is likely it will be replaced at a later time with something more physically-motivated. The "planet/planetismal/KBO" distinction was pushed back to our own solar system, since it will be some time before anyone sees anything that small in another system.
Also of interest is the following link, which gives a history of previous claims for additional planetary members of our solar system : SEDS.
Science, like Nature, must also be tamed, with a view turned towards its preservation.
I've never had trouble remembering the names of the planets, and I totally suck at rote memorization. I just read some interesting stuff about them at an early age and it stuck.
In Sixth Grade, the teacher decided we all had to memorize the names of the presidents and recite them in class. I just couldn't do it. Interesting thing: the current president had just gotten re-elected, and everybody insisted on saying his name twice. I tried to point out that this didn't make sense, since nobody said "Roosevelt, Roosevelt, Roosevelt, Roosevelt". But I wasn't allowed to have an opinion, since I hadn't even done the assignment!
J'aime mieux les méchants que les imbéciles, parce qu'ils se reposent. -- Alexandre Dumas
To be fair, luna is also the closest moon to the sun by a hundred million miles...
"Faith: Belief without evidence in what is told by one who speaks without knowledge, of things without parallel." - A.B.
I have been interested in Astronomy since I was about six years old. Just over forty years. I have heard what you suggest before -- but only in the last few years. And I don't understand it any more this time than I did on the earlier occasions.
Frankly, I strongly suspect it is a false factoid, like that the internet was built to survive a Nuclear War. I strongly suspect it is a bullshit meme that keep being repeated because it sounds cool, but is completely false.
Pray explain what you mean when you say the other 138 moons would float off ?
I am trying to do the "thought experiment" of silently, quietly erasing the principals of those moons, mass and all. I am finding this difficult to do. I don't believe there is any way this could occur, in our Universe.
So, instead I imagined doing something to accelerate a moon, any moon, to the escape velocity of its principal. What happens then? Well, the object accelerated to just beyond a planet's escape velocity will assume an orbit very similar to that of the Planet it just escaped from. Sometime in the last couple of years ago there was a flap about a small object that seemed to have been temporarily captured in the Earth-Moon system. But it turned out to be NASA space debris. It appeared to be the discarded upper stage of an Apollo moon shot.
And some planets are not much more than super dense gas. About the only thing solid on them is their subzero cores which contain things such as frozen/metallic hydrogen.
http://www.gps.caltech.edu/~chad/2004dw/
There are no planets with 'subzero cores'.
A large number of known asteroids are exactly that: clumps of rock weakly held together through their own weak gravitational forces.
This incidentally leads to one of the fears of trying to deflect such an asteroid were it on a collision with the earth -- that it would simply fragment it and cause destruction on a wider scale.
You can never go home again... but I guess you can shop there.
Similarly, Pluto was discovered because it was found that Neptune alone was not sufficient to account for all of Uranus' irregularity.
Actually, no. When Pluto was discovered it was found to be too small to account for the irregularity in Uranus's orbit. When they went back and checked, they found there had been a mistake and there wasn't any irregularity to start with. The discovery of Pluto was an accident.
All cellestial bodies orbit their parent body in an eliptical orbit, not a circular one, and an ellipse has two focal points.
You are correct, however, that when looking at the the orbit of just one single object around one single other, particularly when their masses are very divergent, you can always ignore the focal point that is furthest from the heavier body.
However, when examining how multiple bodies affect _eachother_, it isn't quite as simple (it would be if orbits were circular, but they aren't).
File under 'M' for 'Manic ranting'
We don't know that the gas giants even have solid rocky cores underneath...
But yes, a mass body substantial enough to hold on to an atmosphere could be a valid definition of a planet. Not *the* valid definition since we have planets like Mercury buffeted by solar winds..
Michel
Fedora Project Contribut
In that case, Jupiter isn't a planet either - They're a double-star system. The center of mass of the Sun-Jupiter orbit is outside the photosphere.
This reminds me of Quaoar.
Both are small Kuiper Belt objects. Quaoar was mentioned on Slashdot before.
It's nice to find these mini-planets and give them names. The area beyond Pluto is fascinating, all the more reason why the New Horizons probe should be launched. I hope that Bush's single-minded fixation on Mars doesn't cause this project to be scrapped....
Dr. Demento On The 'Net!
Here are pictures and discussion of the moon's orbit about the sun.
Instead of measuring the distance across an object, as this seems to lead to some problems in our definition, perhaps we should look at it's mass, in respect to the force of gravity between it and our sun.
Newton came up with a very simple equation to figure this out:
f = GMm/r^2
Where f is the force of gravitation between the two objects; G is the universal gravitation constant, 6.67 * 10^-11 Newton*Meters^2/kg^2; M is the mass of our sun; m is the mass of the object in question, and r is the (average) distance between the two.
The smaller the force of gravitation, the less likely that object is to become captured within the sun's gravitational pull. By setting a limit on how low f may drop before the object is no longer considered a planet, we very clearly define what may be considered a planet, what an asteroid, and what just space junk.
This throws into question not relative size, or diameter of the planet, but rather it's average density in respect to the density of our sun, and the distance between the two; ie, the force of gravity between the object and our sun.
Google for universal gravitation for more specifics.
- Kris Kerwin
Kris Kerwin kkerwin@insi__REMOVE_ME__ghtbb.com
The key to preventing an extinction-causing asteroid impact is simply to NOTICE it early enough and have a fast means to get a vehicle there. The reason the asteroid-defeating plans are so hard to create is that we have to wait until the asteroid is near us before we can reach it. By then it's too late. If we can affect it sooner, then exploding it into parts could work really well because the parts would be imparted with enough velocity to spread apart so most of them miss the Earth. Even if an object is headed to strike the earth dead-center, then you only need to deflect it far enough to move it a little more than one earth-radius of distance to the side by the time it gets here and that will make it miss.
(You do need to go a little more than one earth radius because gravity will pull it in - you need to get it far enough out so it will at least slingshot around earth instead of striking it.)
To put this in perspective, if the asteroid was blown up 40 days before impact, that would give us 960 hours for it to move. In 960 hours, an object can move an entire earth radius by going a mere 4.1 miles per hour. So as long as the explosion can impart a velocity of a little over 4.1 miles per hour perpendicular to the course of the asteroid, then the asteroid bits will veer far enough off course to miss. So exploding the asteroid and sending it's parts off in different directions *can* work, if your explosion is big enough to impart that much velocity, and (this is the hard part) you can get a vehicle carrying the bomb out there 40 days before the impacyt.)
The best defense against such an asteroid is a better space program, with faster vehicles that don't require months of prep time to launch. That gives us the time for a simple solution to actually work.
Don't label something "offtopic" unless you know the topic well enough to tell what's on topic.
From Phil Plait's Bad Astronomy: Review of Deep Impact: