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Another New (Minor) Planet In Solar System
jeffsenter writes: "Another new planet (2000 WR106) in our solar system was discovered last week by a U. of Arizona astronomer. The NYTimes has the story (free reg. req.). Like the planetlet (2000 ED173) found in October, this object lies between Neptune and Pluto. The difference is this one is bigger, up to 1/2 the size of Pluto perhaps."
Or try this link instead. Once you get into the hundreds, I think "planetlet" starts making more sense than "planet."
Planetlet? Planette? Heck, we already had planetoid.
Actually the astronomical term "minor planet" has long been used to describe the thousands of identified solar system objects that are neither full-fledged planets nor moons. This new one, WR-106, is a member of the Kuiper Belt, essentially a large amorphous cloud of asteroids outside the orbit of Neptune; hence the official grouping Trnns-Neptunian Objects.
This is an exciting class of discoveries. It was surmised for a number of years but only in the 1990s did significant identifications of these objects begin. Now we're reached the hundreds, and there's likely many more to come, as techniques for locating them are refined. (In a nutshell, using computers to do the same flash image comparisons that Clyde Tombaugh used to find Pluto.)
What's significant about WR-106 is its hypothetical size -- which is far from verified. It could possibly be larger than Ceres (d. 570 mi), in the asteroid belt, which up until now has reigned as the largest minor planet. What this suggests is that the larger objects in the outer solar system are by no means all identified and discovered. Heck, there could even be a full-fledged twin of Mercury, or even Mars, way out in the deep dark. It's possible, and discoveries like WR-106 mean you can't just discount that possibility.
The whole question of Pluto's planethood has never really been open. What reached the press was a badly garbled story of disrespect to Clyde Tombaugh; what really happened is simply that the people who track minor planets wanted to include Pluto (and its almost-as-big moon) as part of the TNO group. There's no question, or at least wasn't, that Pluto would be at the head of that class, just as Ceres is at the head of the list of asteroids. It wasn't about downgrading Pluto, but about recognizing it as the first discovery in a vast new universe of discoveries in our outer solar system.
It's not really important to most astronomers what they're called. We've gone beyond the simplistic question of "how many planets, 6, 7, 8, 9, or 10?" to the full realization that our solar system is made up of an infinite number of objects, from Jupiter-sized gas giants, to rocks like Pluto or Phobos, down to dust specks too small to see let alone count. The list of numbered asteroids is closing on 20,000, and that's just what we can find from Earth!
The importance of this discovery doesn't lie in the headline-grabbing reconsider-what-you-all-learned-in-fourth-grade aspects, but in how this affects the questions of cosmology and planetary formation, as well as the prospects for the future. If our solar system is made up of so many small rocks, it increases the odds that there are more rock-strewn star systems out in the larger galaxy. If our solar system has ore-filled rocks all over the place, that's probably a good omen for anyone contemplating colonizing the outer solar system.
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Not another planet! How am I going to remember its name? We'd have to create (gasp) new mnemonic devices.
My Very Excellent Mother Just Sent Us Nine NGC-11297 Pizzas
People don't like change. Especially the change of something that has been drilled into their heads since the time they were 3. Expect a lot of debate about what to do with these new "mini-planets" between the scientific community and the general public.
there is also some definition that goes like this :
A ``planet'' is an object that has a mass between that of Pluto and the Deuterium-burning threshold* and that forms in orbit around an object that can generate energy by nuclear reactions.
* Deuterium Burning Limit: Objects less massive than 12 Jupiter masses never burn Deuterium nor generate significant energy from any nuclear reactions. Coincidentally this Deuterium-burning limit at 12 Mjup resides near the high-end of the observed planet mass distribution.
...
Corollary #1: Observations may enhance but not authenticate planet status.
Corollary #2: Sharp parameter boundaries for the domain of "planets" can be neither physically nor empirically justified at this time. Objects which have masses and formation histories near the perimeter of the adopted parameter domain constitute part of a natural continuum.
just for those who might be wondering
asteroid n, Astronomy; a rocky body, less than 1000 kilometers across, in orbit around the sun
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