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Hubble Photo of Sedna Suprises Astronomers
waynegoode writes "Soon after the announcement of the discovery of Sedna, the solar system's furthest object and planet wanna-be, the Hubble Space Telescope was pointed at it to answer some of the many questions its discovery generated. The photos were released today and are surprising for what they don't show--a moon. Astronomers were certain it had a moon because of its slow rotation. "I'm completely baffled at the absence of a moon," says Michael Brown, Sedna's discoverer. Story and photo at Universe Today, hubblesite and NASA press release."
Uh?
Pluto is comparable in size with our own moon, and it has a moon of its own.
Asteroid Ida has a moon. Ida is about 56 by 24 by 21 kilometers in size.
Having a moon has nothing to do with size.
Story also here
Small info:
* Sedna is about three-fourths the size of Pluto.
* It takes 10,000 years to orbit the Sun.
* Sedna spins on its axis once every 20 Earth-days.
The object is not there, though there is a very small chance it might have been behind Sedna or transiting in front of it, so that it could not be seen separately from Sedna itself in the Hubble images.
Granted the likelyhood of this isn't great, but I think it is a lot more probable than the explanations suggested in the parent posts.
The other issue is that the planet can only occult the moon if the moon's orbit is edge-on to the Earth. That's true of many moons - consider the Galilean satellites of Jupiter, which eclipse and are eclipsed by their primary on a regular basis - but is very unlikely to be true of such an eccentric object as Sedna. Objects that far out don't adhere well to the ecliptic - they tend to go their own way :-)
Real Daleks don't climb stairs - they level the building.
Myabe because the distant nebulaes and stuff are actually billions times trillions times gazillions times larger than sedna...?
Well from this we deduce that 1 Hubble pixel corresponds to 1,000 miles at 8 billion miles, so 1/8,000,000 radians.
According to the Google calculator = (1/8,000,000) radians = 0.0257831008 arc seconds.
The field of view in the "pretty pictures of objects far away" is simply much larger than 0.025 arc seconds.
Caution! This is a explanation involving a astonomical unit called "Really", that astronomers often use when talking to laymen.
Sedna is Really small and Really far away.
The rest of the universe is Really Really far away, but is also Really, Really Big.
Hubble's lenses, when imaging, take into account these Really's so that when you cancel out the Really's, Sedna ends up small and the rest of the universe ends up Big in hubble pictures.
You are in a twisty maze of processor lines, all alike.
There is a lot of hype here.
Sedna is one pixel with RGB (255,255,255).
You'd expect its moon to be one pixel, with RGB (50,50,50) maybe.
How someone using the buzzwords "extrapolations" and "anti-aliasing" can miss this would be a better question.
Here you go. Asteroid Ida and it's little moon "Dactyl".
Dactyl is about 0.75 x 0.8 x 1.0 miles in size. Imagine that!! Imagine sitting on Dactyl and orbiting Ida. Now, I'm not sure if a rock of 1 mile in diameter can even hold you down.
Does anyone know how to calculate your weight on Dactyl? Size listed above and it's probably 2.2 - 2.9 grams per cubic centimeter.
... the future of that project. The absence of a natural moon which could have been modified a will certainly put a huge dent in G.W's budget since it forces him build from scratch the fortress-moon/deathstar needed to defend US intrests in the region. Then there is the matter of the pesky natives ....
Only to idiots, are orders laws.
-- Henning von Tresckow
I may not be a lawyer ;-) but I have just finished a Ph.D. in astonomy and I've worked with Hubble images (included ACS images) before.
NaSa are wonderful at using Hubble to produce pretty publicity images. I'm not saying that the images of nebulae etc. are not without scientific justification, only that NaSa are very good at presenting them to the public.
These images are more typical of the data taken by Hubble on a day-to-day basis; single filter images (presented in black and white) of faint objects pushing down close to the detection limit of the instruments.
We can think of 4 possibilities for why we do not see a moon around Sedna.
BTW, his site has more information on Sedna.
20%
Assuming its orbit is in the ecliptic plane. This is not a good assumption from Neptun onwards.
Baker's Law: Misery no longer loves company. Nowadays it insists on it
http://www.sigsegv.cx/
Sedna is.. or was classified as, anyway, a Kuyper Belt Object (KBO) so it does not follow the naming system used for other objects. KBO objects are named after gods and goddesses of creations..
Oh, and Inuits would be offended if you call them Red Indian. Any native Americans would, in fact, but Inuits are not even 'red'.
Michel
Fedora Project Contribut
The inner system never sleeps. The outer system never wakes.
Sounds deep, but unfortunately, it is incorrect. Mercury (it doesn't get more "inner" than that) "sleeps" a great deal. Due to its eccentric orbit and bizzarrely-coordinated orbital period and rotational period, a single day on Mercury lasts as long as two of its years! That is to say, its rotational period is exactly two-thirds of its orbital period, meaning "nighttime" on Mercury lasts several Earth months. That's a lot of "sleeping" for a planet in the inner system which, according to you, never sleeps.
Incidentally, while we generally presume Mercury to be a very hot place (and it is, during the day), the temperature on side of the planet that is in nighttime can drop to -150 degrees Celcius.
Like woodworking? Build your own picture frames.
Not really. A system of small moons wouldn't explain the slow rotation, because it takes a big moon relative to Sedna to produce enough tidal action to slow the rotation down.
Fascism trolls keeping me up every night. When I starts a preachin', he HITS ME WITH HIS REICH!
Don't allow Hubble to fall back to Earth. It is still doing good science and can for years to come. New modules for Hubble have already been built and tested and only await a shutle mission to be installed. Call your congressman / woman today. Here is some info from the Mars Society on the work to save Hubble.
JET Program: see Japan, meet intere
The electronic detectors (CCDs) on HST, as on virtually all professional telescopes, are inherently monochrome detectors. During an exposure, the detector is behind one of several filters. There are filters that pass UV light, blue light, green light, red light, infrared light, etc. In many cases, the same bit of sky is observed in multiple filters, one after the other. If these happen to be red, green, and blue filters, you can put the three images in the red, green, and blue channels of a color image, and get something that's approximately true color. The filters are not designed to exactly mimic the human eye's color response; that's not an important concern from a scientific standpoint. If some other combination of three filters is used, they can still be placed in the RGB channels of an image, but the result will be a false-color image. That doesn't mean the color information is meaningless; parts of the nebula that look "blue" in the image probably have something physically different happening than parts that look "red."
Many people have an unrealistic expectation that colors in astronomical images should be exactly correct. That's a hard thing to nail down. As I mentioned above, the filters are not designed for human-vision color fidelity, since that's not relevant to the scientific goals at hand. Also, if you look at a nebula with your eye, even through a very large telescope, you vision will be dominated by the color-insensitive rods, and the nebula will appear quite washed-out. So do you want the publicity pictures to mimic this shortcoming of human vision (that we don't see much color in faint things)?
Back to the topic of the CCDs being monochrome detectors: This is true of the CCD or CMOS detectors in consumer digital cameras, too. But instead of putting the whole detector behind a colored filter, each pixel on the detector is behind a tiny red, green, or blue filter. Thus, each detector pixel is still only recording one of the three colors of light. (The new Foveon chips are an exception to this rule.)
Add to that the fact that we don't know its composition or how long it has been in orbit (it could be a ball of plutonium that was captured from the Kuiper belt in 1976, for all we know), and I have a hard time seeing this as particularly unlikely. Interesting, perhaps, but not unlikely. At its size, the odds of it being able to capture and hold a moon of any size are remote, IMHO, so I would have been surprised if they -had- seen a moon.
That having been said, IANAA.
Check out my sci-fi/humor trilogy at PatriotsBooks.
I believe they address the selling of chemicals in one of the 'episodes' near the bottom.
This was not a case of GWB senior or Reagan going "here's your mustard gas, wink, wink", but more of an american company that was breaking the law by providing known precursors to a country on a prohibited list. There were probably also some political officials at some level who turned blind eyes, received kickbacks, or were asleep at their post.
So, it's not like we should blame GWB for it, but at the same time we have to own up to our responsibilities, as a nation, for often arming dangerous people, either as policy, or as a byproduct of greed by the few.