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First Oort Cloud Object May Have Been Discovered
Posted by
kdawson
on Wed Aug 27, 2008 03:26 AM
from the lands-where-the-jumblies-live dept.
from the lands-where-the-jumblies-live dept.
SpuriousLogic alerts us to the discovery of what may be the first object ever discovered from the inner edge of the Oort cloud. 2006 SQ372 was found on images from the Sloan Digital Sky Survey. Its discoverers theorize that this comet-like object and the planetoid Sedna, first spotted in 2003, might be Oort denizens. Sedna is in a stable orbit but 2006 SQ372 has been perturbed by the gravity of Uranus and/or Neptune, simulations suggest, so its orbital history is unknowable. 2006 SQ372 will travel out to 1,600 AU on this orbit, making it the most distant solar-system object yet found. The Oort cloud is believed to extend ten times that far, or about a quarter of a light-year. "Theoretical models of the formation of the Oort Cloud predict that it should also host a massive inner part, but comets from this region never make it near Earth. To see the long-period comets from the inner region of the Oort Cloud requires observing comets whose orbits always stay well outside Saturn's orbit — like 2006 SQ372."
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The Sun's 10th Planet... Sedna? 636 comments
dsanfte writes "While NASA remains intentionally vague, promising only a news conference Monday, The Australian has the details. The new planet, dubbed Sedna after the Inuit goddess of the sea, is 3 billion km further from the sun than Pluto, and is slightly smaller at 2000km in diameter. This discovery has apparently reignited the debate as to how big a solar object must be in order to qualify as a 'planet', but it is significant nonetheless."
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Planetoid? (Score:5, Insightful)
the planetoid Sedna
Wouldn't that be a plutoid?
Re:Planetoid? (Score:4, Funny)
Wouldn't that be a plutoid?
so he goofed a mickey mouse factoid?
Parent
Re:Planetoid? (Score:5, Informative)
A dwarf planet and a plutoid are not mutually exclusive. A plutoid is a subset of dwarf planets that are further from the Sun than Neptune. Sedna has not yet been designated a dwarf planet or a plutoid because there is currently a debate in the IAU about the characteristics of a body for its self gravity to round it. Sedna is currently classified as a planetoid (or minor planet). However, Sedna is considered a strong candidate to become both a dwarf planet and a plutoid since a) its estimated diameter of ~1500 km is larger than the 800 km that is expected to round a rocky dwarf planet, and b) it is likely made of a significant fraction of ice which would significantly lower the diameter needed to round it. I don't expect the debate in the IAU to be resolved anytime soon, but I think Sedna will be reclassified because its characteristics overwhelmingly support the likelihood that it has enough gravity to round itself.
Parent
Oort Cloud (Score:5, Informative)
Something tells me that a lot of people are going to be looking up Oort Cloud on Wikipedia in the next few minutes... the article summary is nice and scientificky but it hardly explains what's going on in simple terms - the article is actually more summarised than the summary!
For reference, see the article itself or:
http://en.wikipedia.org/wiki/Oort_cloud [wikipedia.org]
Oops, Oort. (Score:3, Interesting)
Offsite backups seem like a good idea to me. How about you?
Re:Oops, Oort. (Score:4, Interesting)
Anybody know if this a theory, or I'm I just ready for bed? I can't seem to find any info on it. Maybe I heard it on Art Bell years ago, in which case I AM ready for bed...
Parent
Re:Oops, Oort. (Score:5, Informative)
Yes, this is the "Nemesis" theory, which was popular in the '70s and '80s for explaining "regular" extinction events. However, the events are less "regular" than suggested by proponents of the theory, and if such a star really existed, Infrared All Sky Surveys would have detected it by now. They haven't, so it doesn't exist.
Parent
Re: (Score:3, Informative)
I thought the latest theory was that Oort cloud disruption occurred as our sun fluctuated up and down through our arm of the galaxy, as we circle around the core?
Re:Oops, Oort. (Score:5, Informative)
Yes, there was a serious theory for a while that a small dim star called "Nemesis" orbits the Sun and would disrupt the Oort could every 40 million years or so sending a hail of comets into the inner solar system which is responsible for mass extinctions on Earth. It never really had many supporters.
I addition to Nemesis, which at least was a theory espoused by legitimate astronomers, many kooks are convinced that there is a weird giant planet out in that same area which swings by Earth every few thousand years and is supposedly the home to a race of lizard people who communicated with the Sumerians. Now go to bed or the lizard people will get you.
Parent
Re:Oops, Oort. (Score:5, Informative)
From the Wikipedia article [wikipedia.org]:
The outer Oort cloud [...]. Its total mass is not known with certainty, but, assuming that Halley's comet is a suitable prototype for all comets within the outer Oort cloud, the estimated combined mass is 3x10^28 grams, or roughly five times the mass of the Earth. Earlier it was thought to be more massive (up to 380 Earth masses), but improved knowledge of the size distribution of long-period comets has led to much lower estimates. The mass of the inner Oort cloud is not currently known.
Parent
Re: (Score:3, Informative)
You missed this in the Wikipedia article:
Re:Oops, Oort. (Score:5, Informative)
Incorrect, the sum of the mass of the Oort cloud objects *might* be larger than the Earth's mass, maybe even a few Earth masses, but it is certainly not "far more than the mass of the sun and all the planets".
While an Earth sized planet might exist in the Oort cloud and not be detected, it is essentially impossible for anything Jupiter-sized to exist there, for two reasons: (a) Infrared all-sky surveys would have detected it by now and (b) a massive object like that would cause a significant detectable influx of smaller objects (comets) from the region where it exists. No such "preferred" direction is detected in long-period comets, and the number of long-period comets we find is at least an order of magnitude lower than we would see if there really was such a massive object out there.
Parent
Re: (Score:3, Insightful)
The total mass is probably much larger than the mass of its larger objects. Remember the Oort cloud is supposed to be very large and, thus, very sparse. You can have a couple solar systems worth of mass out there and it would still look like a pretty good vacuum. There would be no distant Jupiter (not a hot one, at least) and no dark star, but that would not preclude the total mass of the cloud from exceeding the mass of the rest of the solar system.
To put it simply, nobody knows its mass and all estimates
Re: (Score:3, Insightful)
Incorrect. He did not say there were "Jupiter-sized" or even "Earth-sized" objects.
He Said: "... SUM of the mass of oort cloud objects is far more than the mass of the sun and all the planets. "
What you are saying is totally different. We KNOW with (reasonable) confidence there are no Jupiter sized objects in the Oort. We believe with (somewhat reasonable) confidence there is no Earth sized object in the Oort (although there is so much out there, I wouldn't bet on it).
What he said is the sum of all the smal
Re:Oops, Oort. (Score:5, Funny)
The Oort cloud could hold a planetary mass comet on a collision course with Earth and we would know about it only right before the event or just after.
It's probably a conspiracy to build A Really Big bypass.
Someone should go down to the local planning department to see if any demolition orders are on file.
Parent
Re:Oops, Oort. (Score:5, Funny)
I am pretty sure we would notice something was amiss during the collision as well.
Parent
Re:Oops, Oort. (Score:4, Informative)
Just to make you paranoid, the sum of the mass of oort cloud objects is far more than the mass of the sun and all the planets
Not supposed to be. The mass in the Oort cloud can be estimated by assuming some sort of mass function (i.e., a distributon of number, and thus total mass, with the mass of the object. Unless there a some unknown big objects out there, the total mass is order one [harvard.edu] Earth mass to maybe 100 [sciencemag.org] Earth masses. And, there have been negative searches [harvard.edu] in the IR for very large (Jupiter size and larger) objects, so it's almost certainly nowhere near as large as 1 solar mass.
It is interesting that the "knots" seen in the Helix Nebulae are likely to be super-comets (Sedna sized bodies ablating under the bright glare of the dying central star), so if you want to get a look at an Oort cloud, here is a good one [hubblesite.org].
Parent
First or Second? (Score:4, Informative)
It seems that Sedna [wikipedia.org] is sometimes regarded as an inner Oort Cloud object. But this seems to be disputed since it's a lot closer than the supposed location of the Oort Cloud but much farther away than the Kuiper Belt objects.
They should rename it "Urectum"... (Score:3, Funny)
SQ372 has been perturbed by the gravity of Uranus
I can't help but feel there's a "Yo Mama" joke in there somewhere...
interraction with the Kuiper Belt (Score:3, Interesting)
I'm willing to go as far as to say it was one of these objects that was responsible for the destruction of a now ghost planet between Mars and Jupiter.
Re: (Score:3, Informative)
No, that was the Martians. [wikipedia.org]
Re:interraction with the Kuiper Belt (Score:5, Interesting)
Let me be pedantic for a minute and state that the Kuiper Belt != the Oort cloud.
The Kuiper Belt and the scattered disc have been studied/observed quite a bit. The Oort cloud, on the other hand, is hypothetical (which certainly does not mean that it doesnt exist). The "boundaries" of the inner Oort cloud are thought to begin well beyond the scattered disk, which in turn extends beyond the Kuiper belt (although the two may well overlap).
Parent
Not an Oort Cloud object (Score:4, Interesting)
Too much hyping. This object seems to be a scattered Kiper Belt object than an Oort Cloud object. Why? Its orbit crosses Neptune's orbit, which means it is strongly influenced by the planet's gravity. Sedna is different, because it never comes near Neptune. That doesn't mean that Sedna is an Oort Cloud object since its aphelion (most distant point of orbit) is not far enough. This newly-found object has a longer orbit, but compared to some long-period comets that originate from the Cloud and which can take several tens of thousands to millions of years to complete one orbit this is not at all unusual.
This could be from another solar system (Score:3, Interesting)
Sedna [arxiv.org] is supposed to have resulted from an interaction between the Oort cloud and a distant passage of another Star in the past. That means that there is a good chance (30% or so) that it belonged to the OTHER stars Oort cloud.
2006 SQ372 has an even more irregular orbit which is unstable to boot. The same sort of arguments will apply to this object, and so there is a decent chance that it, too, will prove to come from another solar system.
Re:I thought it was Neo. (Score:4, Funny)
Was I the only one that saw a 'Matrix' reference there?
Yes, yes you were...
Parent