I never knew...
Uranus was a gas giant...
Boffins have long hypothesised the existence of a large, but thus far unseen, celestial body in our Solar System, somewhere beyond the orbit of Pluto, but NASA's WISE survey has found no sign of the mysterious "Planet X". A nearby star stands out in red in this image from the Second Generation Digitized Sky Survey by WISE …
Hmm ... Register Units?
About 8 mReg?
(Being 8/1000 of the distance from here to Regulus. Although mysteriously, the Register-star is in the constellation of Leo (probably eating its entrails...), and will be obscured by 163 Erigone on the morning of March 20th - expect articles to go missing or be delayed around that time.)
How many brontosaurus's is that?
http://www.theregister.co.uk/2007/08/24/vulture_central_standards/
+1 to Psyx.
However, I believe the theory as to how the Oort cloud formed, and therefore what it is composed of, precludes objects that large existing in any great number.
There are likely such objects in the inner Oort region* but I believe the area of interest is the outer Oort Cloud as the data that pointed to this hypothetical planet's existence was based on long period comets originating in the (outer) Oort Cloud.
It is my understanding that the Oort Cloud consists almost entirely of small comets flung out during the creation of the solar system and if such a large planet/dwarf star were to exist, it would have been captured, rather than flung out.
Does that sound right? It's all hypothetical anyway as we can't detect anything smaller/dimmer than about Jupiter out there anyway!
* - Well, by definition, there must be as it was proposed to exist to accommodate the dwarf planet Sedna when it was realised that it was too far out to be part of the Kuiper Belt but too close in to be part of the (hypothetical) Oort Cloud.
> the effects of gravity fall off exponentially
As any fule kno, gravity obeys an inverse square law, F = GMm/r^2
If it was exponential, it would have some constant k to the power of r in the denominator.
Sorry to nitpick, but 'exponential' has a useful exact meaning which is literally diluted by using it wrongly.
:)
I seem to recall something about the circumference of ignorance, said by someone whose words were worth listening to.
In any case, I feel that scientific progress in astronomy is an exciting field these days. In 2000, we thought planetary systems were rather scarce. Since then, we've had confirmation that at least one-third of the systems that we have surveyed have planets in them. We've gone from hypothesizing Earth-like planets to actually finding planets in the Goldilocks zone.
Now we realize that our "backyard" is bigger than we thought it was ? No problem, we'll work that out too. It should provide a good learning experience as well, teach us how to survey and map a system for when we arrive at a new solar system - sometime in this millennia or the next.
Exciting times !
No it does not. That is not how black holes work. Look it up. Their effect on the neighborhood is no different to a star or planet. They just have the size to go with their name.
As a thought experiment, try getting stuck in (or proposing the earth get effected by) a black hole. Try it. Propose any means you wish. You may find some small problems actually achieving it.
"I'd think that a smaller planet would also be a risk of upsetting the potential comments of the Oort cloud though."
Luckily, the rocks have a pretty good founding in physics and know that a small planet is not going to plough through widely scattered debris in a sphere over a light year in diameter and cause anything approaching chaos, because small planets don't have much gravity and the oort cloud isn't some kind of Star Wars asteroid field with rocks every 200m.
Seriously: The Oort cloud is far larger with far less debris than you think it is.
You do need to start looking closer to home, dear!
One thing the Nemesis hypothesis has always been very clear on is the size of the orbit - in order to get the period right it needs a semi-major axis of around 95,000 AU. These chaps can make meaningful assertions up to only 42% of that distance and less than 7.5% of the volume of space, and this is somehow "proof"?
Yes, Nemesis is unlikely but it is a legitimate minority opinion, dismissing it as crackpot science is in itself a demonstration of scientific ignorance, since the whole idea is surprisingly and annoyingly difficult to conclusively disprove. In their eagerness to "prove" the falsehood of the theory they are guilty of far worse junk science.
But a star that close to the Sun, even if it is class Y brown dwarf it would have showed up like a bright beacon to the IRAS and/or ISO missions, let alone any of the terrestrial IR-sensitive telescopes. Also the theoretical orbital parameters for Nemesis (consistent with the extinction pattern) has been worked out a long time ago, and we know in what part of the sky we should be looking, but nothing is there!
BTW, the extinction pattern data is based on a very small sample set that is statistically not significant. Basically the uncertainties outweigh the conclusions.
... but presumably the proposed Nemesis is supposed to have a highly elliptical orbit? In which case - assuming it isn't currently at/near an extrema, the liklihood of spotting it might be higher, although of course it's slower moving out there and less likely to dwell in range. Also, might it not be likely to share the same orbital plane as the (inner) Oort cloud? - perhaps relaxing your 0.4^3~=0.07 to about ~ .4^2 ~= 0.16.
While the authors may well be over confident, it seems to me that without further detail, your 0.4^3 is perhaps to be a rather too stringent a bound on probability.
(correctlions/clarifications welcome)
presumably the proposed Nemesis is supposed to have a highly elliptical orbit? In which case - assuming it isn't currently at/near an extrema, the liklihood of spotting it might be higher...
Orbital mechanics have the effect that the closer in a body to whatever it is orbiting the faster it travels, before slowing down as it moves further away from that body again - if you think about it it's simple conservation of energy, as kinetic energy is traded for potential and vice versa. The net effect is that arguing for a highly elliptical orbit pushes out the average distance at any given time quite considerably, since the body spend most of its time traveling slowly through the more distant part of its orbit, before quickly sweeping through the closer portion and returning to a greater distance.
In any event, for the theory to hold it almost needs the reverse, while the orbit doesn't have to be perfectly circular it can't be highly eccentric. The projected orbit is huge - a radius of 1½ light years. The more eccentric it becomes the further the hypothetical body moves away from the Sun at it's outermost limit and if it gets too far the Sun ceases to be gravitationally dominant. Even if in one particular pass it doesn't come close enough to anything else to be perturbed out of orbit, you would expect precession of the argument of perihelion over cosmological time, which would have the effect of flinging it out in a slightly different direction on each orbit. That increases the chances of an eccentrically orbiting body being lost forever.
Given they've got the orbit worked out they also know based on the extinction events where on the orbit the planet ought to be. So you don't have to do a whole sky survey. If those calculations show it outside the range of experimental observation, there would have been no point in conducting the exercise in the first place, at least vis-a-vie testing the Nemesis hypothesis.
"These chaps can make meaningful assertions up to only 42% of that distance "
Re: WISE: "a Jupiter-mass object out to 1 light year (63,000 AU), where it would still be within the Sun's zone of gravitational control. A larger object of 2–3 Jupiter masses would be visible at a distance of up to 7–10 light years."
So... we should have found it. More to the point, we should have noted some - any - kind of other evidence. We haven't. And we've looked several times. That's not 'eagerness to throw out a theory' at all.
"the whole idea is surprisingly and annoyingly difficult to conclusively disprove."
Lack of evidence is not evidence. It is impossible to prove that something undetectable does not exist, as atheists have been banging their head against the wall trying to explain for decades. However, all of our best surveys can't find it, nobody has ever spotted it with a telescope, nobody has ever found any gravitic influence that could be attributed to it in modern times, and the best reasoning for its existence is a rough collaboration with the time of extinction events... which might or might not all be related to rocks falling from the sky.
Nemesis remains a fringe theory because zero evidence has been turned up in its favour. And it will rightfully remain a fringe theory.
a Jupiter-mass object out to 1 light year (63,000 AU), where it would still be within the Sun's zone of gravitational control. A larger object of 2–3 Jupiter masses would be visible at a distance of up to 7–10 light years."
Is that the sum total of your evidence? Quoting Wikipedia verbatim about the technical capabilities of WISE, rather than what is has actually been used for to date?
In other words you are completely ignoring the work that the WISE team have done, which they have announced now, restricting their claims to what may legitimately be claimed based on that work. Instead you have substituted what WISE is theoretically capable of, as if once you have the instrument you don't even need to turn it on to observe the null result. That isn't a scientifically robust argument, you wouldn't even accept that in everyday conversation.
Nemesis remains a fringe theory because zero evidence has been turned up in its favour. And it will rightfully remain a fringe theory.
You are overlooking several factors here. Firstly you choose to ignore the fossil evidence that led to the hypothesis being proposed in the first instance. You ignore the geological evidence to the same effect - sure it is a little sketchy but it is highly suggestive. You are completely ignoring the fact it has been published repeatedly in peer reviewed journals. You ignore that process of expert review, who concluded the theory had merit in order for it to be published, because you know better than them.
So, you ignore or dismiss evidence that is contrary to your position. You throw in irrelevant factors that do nothing to support your case as if they were final trump cards. You ignore the opinions of experts. Those are the hallmarks of a scientifically illiterate crackpot theory, not a properly published, legitimate proposal. Just because the theory naturally appeals to the "end of the world is nigh" brigade doesn't make it any less credible.
"Firstly you choose to ignore the fossil evidence that led to the hypothesis being proposed in the first instance."
Not at all. Small sample size and more noise than signal in the data suggests that the most likely cause was not some invisible gas giant that has now been observationally shown to not be within one light year.
It's as likely that a rouge planet passed on occasion and tossed a comet or two about, changes in the geography of the planet altered the environment and the occasional oversuccessful pathogen could have caused many of the mass extinctions or any combination thereof.
The problem is small sample size and a lot of noise.
People see patterns everywhere. But, seeing a pattern does not make it so. There really aren't white dragons flying about, they're still only clouds.
Not at all. Small sample size and more noise than signal in the data suggests that the most likely cause was not some invisible gas giant that has now been observationally shown to not be within one light year.
Where's your evidence? As has already been pointed out, the very evidence you cite explicitly does not make that assertion but limits the distance to a much smaller region of space. Repeating your assertion doesn't make it true, it reveals a lack of basic comprehension.
The problem is small sample size and a lot of noise.
More data would be helpful but we have what we have. Even with that it meets the usual criteria to be regarded as statistically significant, i.e. less than a 5% chance of a random result. That doesn't rule out a freak chance result but it does rule out arguing statistical insignificance. Bear in mind that this pattern was noted before the hypothesis was advanced and independently of its proponents.
Less, it's a theory that needs to be treated with a healthy degree of skepticism, but that does mean you can simply make stuff up to "disprove" it. If the hypothesis wasn't taken seriously why would the people running Wise take the trouble to even consider it? As Fiona pointed out, what do you know that these peer-reviewed scientists don't?
This one doesn't require evidence in the scientific sense. It is defined by the principles established in the rigorously tested mathematics of statistical analysis. If the signal does not significantly exceed the noise you don't have a signal. The signal that would be required in this instance isn't more scans of the local neighborhood, it would be more extinction events in the geological record. That isn't going to happen.
Therefore the Nemesis hypothesis properly belongs on the crackpot theory pile. And every once in a while when you have a fancy new piece of equipment you'd like to run through its paces, you can pull the crackpot theory off the pile and use your equipment to test it. IF you find something to support it you move it to the science pile, otherwise you put it back where you found it.
what do you know that these peer-reviewed scientists don't? Well, for one I've met some of those peer reviewers. They aren't quite as sane as you'd like to think.
For another, I know one of the a number of the tenured professors at one of the mentioned authors alma maters having studied there myself. Most of them are top notch thinkers. But there was one loon on the staff who also didn't understand the importance of the signal to noise ratio issue. Every year he'd tell his liberal arts core requirements classes that all UFO sightings are the results of comets and uses the same flawed arguments you present here. Just checked the faculty listing and he seems to be gone.
"Is that the sum total of your evidence?"
I don't think 'evidence' means what you want it to mean. My quote is not 'evidence', it is indicative as to why there is no evidence that your own pet theory is correct. The WISE team have already announced that they're confident that there are no slowly simmering brown dwarfs or objects larger than Jupiter out there. The Oort cloud is stupidly big and it takes a big lump of stuff to shake it up enough to rain destruction down upon us. We haven't seen anything big enough, despite looking.
Yeah, it'd be fun to have a brown dwarf or something several Jupiter-masses flying around out there, but there is zero evidence. zero.
"You are overlooking several factors here. Firstly you choose to ignore the fossil evidence that led to the hypothesis being proposed in the first instance. "
No I don't. I just don't make reference to it in a paragraph. What I write is not the sum total of my thoughts or knowledge. The fossil evidence of the regularity and cause of extinction events is still under debate. It was a hunch that spawned the theory, based on somewhat shaky statistical data on extinctions.
"You are completely ignoring the fact it has been published repeatedly in peer reviewed journals."
I don't think peer reviewed means what you want it to mean.
Lots of theories are published. The point of publication isn't to prove anything, but to put up a target to have rocks thrown at it. It's a plausible theory on paper, but that was then, this is now, and the theory has lost rather than gained traction since inception. The theory is weaker than when first published because we have discovered more, and what we have discovered is not supportive of the theory.
"So, you ignore or dismiss evidence that is contrary to your position."
No I don't. I just don't waste time agreeing with you over the course of a paragraph, because I'm not about to write a list of things that I agree with. You have likewise ignored General Relativity in your post, as well as turnips, Holsten Pils and Alpha Centuri. That's very ignorant of you to try to ignore the existance of turnips, against all evidence to the contrary.
Again: Fringe Theory because it's a supposition based upon evidence that isn't either proven or conclusive and since publication absolutely nothing has been seen in space to support it.
Assuming there is something orbiting our sun at a distance and occasionally tossing comets our way, why does it have to be a normal planetary body? Maybe the reason we can't see it is because it is a clump of dark matter (assuming, of course, that there is such a thing as dark matter and it isn't just a convenient placeholder for a misunderstanding of physics)
A brown dwarf captured by our sun would serve the same purpose, be effectively invisible, and as a result of capture would have a very eccentric orbit.