Slashdot Mirror
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."
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.
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.
the pictures are taken using filters, not normal light, high intensity x-ray, microwave, IR...the whole deal....they are also taken in sequence, to produce multiple images of the object for sub pixel extrapolation....as a possibility described in an above post. They may have "missed it" in this round of pictures but it is highly unlikely...their guesses may have not accounted for some other gravitational body.
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..."
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.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Friends don't let friends enable ecmascript.
Which other Solar Systems would you be comparing it to? We can only notice the larger planets eg Jupiter size etc in other solar systems.
Video Game cheats, hints a
Are astrologers calling Sedna a "planet" or an "asteroid" - ? Since the 50's they've been waiting to ease the burden on Mercury and Venus, who currently have to rule two signs at once (Mercury rules Gemini and Virgo, Venus rules Taurus and Libra.) I've been reading an astrological course book from 1952, and they were absolutely convinced, since they'd just found Pluto, that there would be at least 2 more planets behind it, one to rule Gemini and one to rule Taurus. (Personally, I think new planets should take over for Virgo and Libra, but that's my modern opinion.)
Offtopic? Only if you've never read a horoscope.
The House Between - Original Sci-Fi Series
or perhaps the moon just has a low albedo. Maybe we can rename the moon "Krylon matte black"
Escape velocity would have been more informative, which using your values of r and rho comes out to .9 m/s or about 3.2 km/hr. Just trying to walk would cause you to fly off the surface, though I guess you'd still be stuck orbiting Ida.
"I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show
Maybe it's not such a coincidence. If the moon played a critical role in the evolution of complex life for instance, the observation of this supposed coincidence would be a case of an observer relative observation.
Under this hypothesis, if the moon wasn't so, we wouldn't be here to observe it and likewise for any other alien lifeforms. It follows then that although such a probably for any arbitrary planet is very low, there is a high probability that such a moon orbits a planet that has evolved complex life capable of observing it.
Doubtless, with me rambling on about aliens, I'm now sounding like an incomprehensible crackpot.