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The Tenth Planet Shrinks Under Hubble's Gaze
starexplorer2001 writes "An object called the 10th planet by some astronomers is not as large as previously thought. New images of 2003 UB313 (aka Xena) were delivered by the Hubble Telescope and showed up as only 1.5 pixels! Now, some are calling to demote Pluto and kill Xena."
A pixel is small, but nowhere near subatomic. It's measured only in microns.
When photons are distributed over the CCD surfrace, it has some measureable shape (e.g., Gaussian) which can be fitted as such to characterize the shape. The quoted size of 1.5 pixel is, I think, the FWHM of the fitted Gaussian function that characterize its source.
A pixel is small, but nowhere near subatomic. It's measured only in microns
By atomic, the author means it cannot be divided further. This was the original meaning of atom. Atomic is a word used in computer science to indicate an operation that can't be interrupted. It either happens completely, or doesn't happen at all.
AccountKiller
As every Dr. Who fanboy knows, the tenth planet is named Mondas. http://www.drwhoguide.com/who_2d.htm/. What is slashdot coming to?
It's because the word planet isn't really a scientific word. There's no hard point where something becomes a planet and where it's not a planet. Words like planet are really just our own convienent language definitions. Arguing about whether something is a planet or not is a little like arguing whether something is a chair or not. It only matters based upon useage.
AccountKiller
It can be derived with trigonometry:
(angle)*distance_to_the_object == size_of_the_planet
which are
(1.5pixel*0.025"/pixel)/(60*60*57.3radian/") * 100AU * 1.5e8 km/AU ~ 2700km.
If you read the article, you'll find that the size is only 1400km, though.
The difference results from the fact that the measured size of 1.5 pixel
includes the size of its point spread function for the HST/ACS/HRC (i.e.,
even a true point source show some finite size in optics...something we
cannot beat).
First of all, IANAA (an astronomer).
:)
[rant]
It's truly amazing that we can see things so far away with our little technology; but ultimately, humans have made it so far as the moon... with respect to our sandbox in the universe, that's not very far. Jupiter and Mars are completely different things - they probably were created via entirely different processes. Mars is a dusty rock that gets hot & cold a lot. Jupiter is a massive ball of gas that has thunderstorms with its moons; I read somewhere that one of Jupiter's moons has a tidal terrain. Could you imagine the crust of the Earth rising and falling some-odd hundred meters as the moon went by? One (many?) of Jupiters' moons has this property.
We need a name for balls of mass (whether a few km in diameter or an astronomical unit, e.g. 93 million miles, in diameter) that orbit stars for a living. If that's a planet, fine. Sounds like comets, Pluto, Xena, and everything else that orbits a star is a planet. Otherwise, a "planet" is a name for the eight terrestrial entities that astronomers have known about for centuries... and we still need a name/class system for things that orbit parent stars. Many (most?) argue that comets and the like are not planets because they came to be and exist in a different way than our traditional "planets"... but our own (8 or 9) planets are so very different to begin with, that if you think about it long enough, they're all too radically different to be in the same class. We may like to think we know how Jupiter and Mars and Earth and the Moon were created; that crap happened so long ago, it's safe to say that humans have no way of knowing - none of us were there.
I like the second article, which suggests we demote Pluto and Xena (and similar objects) to "dwarf" planets.
We're only human! For a long time we thought matter and energy were two different things; now, the fact that matter is considered "solid" is coming into question. It goes to show how little we really know to begin with, and arguing the definition of a "planet" is as useful to our curiosities as arguing the difference between a rabbit turd and a cow pie.
[/rant]
So as not to only rant, I thought I would try to be informative as well.
If anyone would like to see Xena, here's a page with a decent shot. The actual NASA feature about the recent picture is here.
Well, what kind of a name should that be anyway? Xena is not a roman god or goddess, not even a small one like Luna, Nike or Pluto.
So if this object should be called a planet, here's the proper list of names to choose from:
Acca Larentia, Alemonia, Anna Perenna, Carmenta, Carna, Consus, Dea Dia, Feronia, Flora, Fons, Furrina, Maia, Nike, Ops, Pales, Pomona, Portunus, Robigus, Silvanus, Veiovis, Vertumnus, Volturnus
everything else is not acceptable.
"The more prohibitions there are, The poorer the people will be" -- Lao Tse
All the Pixels around it were black except for one that was white, and one next to it that was grey, 1/2 white, 1/2 black. The pixel averages everything in the space it covers. I don't know if they actually use black or white or not, but that's how it works. Does that simplify things?
Someone save me from this sanity.
Acually Uranus was supposed to be called George's Star (only in latin) for King George III, if the discoverer (William Herschel) had had his way.
Hey, you'd have "shrinkage" too if you were covered with shiny methane ice!
... and it formed some million years ago.
p.s. Galle Crater / Argyre Planitia is not "new" by any definition. It was seen by Viking in 1976