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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."
When will G.W. announce a manned mission to look for oil?
"Well, it took an hour to write, I thought it would take an hour to read."
It's an absence of a space station!
with all of my astronomical knowledge the only thing i can come up with is aliens playing some sort of april's fools day joke. but this begs to ask "do alien's celebrate april fool's day or some other weird alien day?" maybe they don't call it april
any other interesting things that didn't happen today?
the sun rose so it can't be that....
water is still wet...
i'm baffled.
They said there was a very small chance that it's companion rock could be behind or in front of it, what kind of percantage are we talking about? You have to figure that the "Sedna moon" would spend at least 20% of it's time in front of or behind the planet (relative to Hubble). Imagine trying to see the moon from a telescope on Sedna, it wouldn't always be on either side, sometimes the Earth would hide it. Maybe they just need to take another photo when Hubble has another oppurtunity.
It would be surprising that Senda has a moon. After all, Sedna itself is comparable in size with our own moon (Sedna has less than 1700 Km in diameter, and our moon has around 3500 Km in size).
:-) I am sure that somebody searched for it.
Now I am wondering if our Moon has another moon orbiting around
Don't try to use the force. Do or do not, there is no try.
'Astronomers were surprised by what they did not see, a moon. The hubble telescope helped solve the problem when honed onto Sedna itself. The planet's oddly erratic, eliptical orbit is due to a giant mass on it's far side. Colon Powell presented the Hubble photographs today in a speech before the United Nations. The photographs detail the until now, 'unknown mass' that was altering Sedna's orbit. "It is clear from these photos" he said "that we have found the Iraqi weapons of mass destruction".
It is unclear how Saddam Hussein delivered and stockpiled the weapons on Sedna, but the blury photographic proof shows beyond a shadow of a doubt that the administration was in the Right from the beginning. NASA was unavailable for comment.
At a distance of over 8 billion miles, Sedna is so far away it is reduced to one picture element (pixel) in the image taken in high-resolution mode with Hubble's Advanced Camera for Surveys. This image sets an upper limit on Sedna's size of 1,000 miles in diameter.
So if the so-called planet is the size of one pixel, how do they expect to see a smaller moon?
And, yes, I'm quite aware of techniques such as extrapolations, anti-aliasing etc. which *may* help extract a smaller-than-1-pixel object using a series of 35 pictures, but I'd speculate that NASA's assertion that Sedna does not have a moon is premature.
Those who can, do. Those who can't, consult.
The slow rotation maybe due to the material the planet is made out of...haven't done enough research...but the limited work i've done on planetary rotation and gravity tells me two things.
The slow rotation may account for a moon or child body which was able to escape the rotational cycle, or was flung off into space during its creation. Which is FAR FAR more likely given its distance from the sun
The other reason maybe attributed to the fact that it is beyond the astroid belt, and is the furthest satellite we've discovered yet. Although it is a small target, it maybe the solar system's first line of defense (eg a riot shield) although not a good one. That could account for both slow/erratic rotation or a missing orbital body.
Its more likely to have had a moon that slowed its rotation but then the moon somehow got lost.
Things can get messy out there in the kupier belt. Its not a place where you want to be alone late at night.
This is my sig, show me yours
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.
Sorry, that won't work. Basic probability: even if it got hit by an asteroid, the chances that it had exactly the amount of momentum to slow down Sedna's angular velocity to near-zero would be infinitesimal. You could say that it's still not impossible, but then that's precisely what surprises astronomers: very-low-probability events. Of course such cosmic coindicences do happen, such as the moon's angular diameter being almost equal to the sun's when viewed from the earth, but far more often, it indicates a gap either in our observations or our theories.
I really pity the people on Sedna. Without a moon, how can they ever hope to get to Mars?
it's the moon!
(the planet is hiding behind it)....
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sigamajig...
Hubble can take pretty (for me as a non-astronomer) pictures of objects far away and in the past [...] and yet it can't take a picture of something within our system larger than a pixel.
Now you may start to get a sense of just how mind-freakingly big some interstellar objects are. This logarithmic maps of the universe should help put things in perspective. Once you've got the image, start from the very bottom and work your way up. And keep repeating to yourself, "another order of magnitude... and another order of magnitude... and another..."
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.
We really need to replace Hubble with a telescope that won't challenge us so much.
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.
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.
The collision theory is extraordinarily unlikely, although of course in a sense possible. A few more likely scenarios strike me though.
Remember that Sedna itself is so small the Hubble can't resolve it. So Sednas companion could be quite tiny and still large enough to affect it. If it has a very small companion with a very low reflectivity, would it be surprising if Hubble didn't pick it up immediately? I'm not an astronomer, and there may be something I'm missing, but that seems quite plausible to me.
It also seems possible that it was part of a binary system earlier and lost its companion, or that it's rotation rate was affected by one or more near misses out in the kuiper belt. We don't know the history of this object at all, we barely even know it exists. It is cool that an initial prediction seems to be a failure here, because that indicates a potential to learn new things, but at the same time it's hardly surprising given how small and far away the thing is and how difficult this makes it to detect and measure.
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Friends don't let friends enable ecmascript.
We can think of 4 possibilities for why we do not see a moon around Sedna.
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.
I want to say how refreshing it is in this day and age that a man can admit that he possibly made a mistake, or that even better, he doesn't really know. Taking some responsibility is nice to see nowadays. I know this scientist doesn't hold a publicly elected position, so he can say things off the cuff. I've probably just been watching too much c-span lately.
Th
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.)