This could be big. At the very least its an interesting discovery, but there's a chance it might change our view of the solar system.

http://arxiv.org/pdf/1512.02652.pdf

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Based off the range of possibilities (large & dark TNO, Super-Earth at 300 AU, closest Brown Dwarf - or unsaid - a new type of object), this is going to be one of the major discoveries of 2015, no matter what it turns out to be.

I'm going to stay cautiously optimistic here and say this looks great. However, this is extremely early for any real conclusions I think.

Mike Brown (and others) is rather dismissive:






https://twitter.com/plutokiller/status/674800207284928512

https://twitter.com/plutokiller/status/674804436150018048

It seems to boil down to that this would have to be a rather extreme chance discovery in order to be real.

They are making this claim based on two observation?

Most of the asteroid searches use several observations to eliminate false positives from variable stars and other transients.

Maybe I'm missing something, but making two observations of a signal near Alpha Centauri and concluding that it's an object in our solar system seems to me like making two observations of a signal near Jupiter and concluding that it's a satellite of the Earth.

Did you read section 4.1? They certainly try to address why the object is not associated with alpha Cen. As I read it, the basic argument is that it's too bright to be at that distance and not have been seen previously.

Statistically I agree, the chance that the object just happened to be in line with alpha Cen but not associated with it seem very low.

Assuming this object is real, the most likely explanation can't be discussed here due to rule 1.3.

I agree that the chance alignment is worrying. I have no problem with an extreme TNO having a random inclination to the ecliptic, and I'm also open to the idea that WISE might have missed moving sources in crowded stellar fields, but what are the chances that this object just happens to be right next to the closest stellar pair in the sky when ALMA starts looking at it? That doesn't mean it couldn't be something very interesting (my favourite outcome would be a bigger-than-Pluto object at over a thousand AU) but what if its some weird instrumental glitch with this new instrument?

I wonder if this paper will get past pre-print and actually get published in a journal?

P

Haha, is this some new way to get around the rule? 'It's probably a rule 1.3.'

Joking aside, I think it entirely possible for an object to go missed in past surveys. Completely possible and maybe even likely. Does it mean this object fits into that category? No way to know until many more readings are taken. I also do not think it should so quickly be dismissed as many have done. Its a question mark at the moment. Nonetheless, excitement that ends in disappointment due to faulty data can be bad for public outreach all the same though.

What other instruments are there that might be able to confirm or disconfirm the ALMA team's findings? Is this the sort of thing where there might be existing data that could be analyzed? If ALMA's the only instrument that's capable of detecting this (putative) object, it's going to be a long wait to be sure it's not an artifact. (That is, an instrumental or methodological artifact, not a Rule 1.3.)

Well, WISE has ruled out brown dwarfs within the solar system. Here's a SciAm article about the whole thing.

Have yet to read all the text, though if it has the proper motion of A Centauri it should be associated with it. I wonder if it is something bright at millimeter wavelengths and dim at visible wavelengths. Some sort of companion in the Alpha Centauri system, like a large planet or brown dwarf? Maybe it's a brown dwarf that WISE couldn't see in the glare next to A Centauri.

They do address WISE and question why it would only be detectable now, suggesting that there was too much glare from AC or that it may have been too cold for WISE to catch.I think they've covered the bases as to this being tenuous evidence. Supposing it actually exists and that it isn't in the Solar System because it can't be accounted for in models, maybe it is a very distant, very old dwarf or sorts that is traveling between the systems.

The signal-to-noise ratio for the two "detections" are about 3.6 and 2.1, and are in different locations. For Kepler, an SNR of 7.1 was used for most of the published work, and that ends up creating a lot of false detections. I think the simple explanation is that they took two spurious events which weren't even in the same location and concluded that they detected an object that moved and that has a spectral profile matching those two rather low SNRs.

SNRs of 2 to 4 ought to be occurring in lots of places where there is no real object. That's how noise works – sometimes it's more, and sometimes it's less. An SNR of 7 is hard to get without a real phenomenon behind it – and yet it's not impossible. An SNR<4 is not going to be very rare in a large data set. In Fig. 1 (left), we can see lots of non-black pixels almost as bright as the one they circled. In Fig. 1 (right), what they circle does indeed appear somewhat rare.

The fact that the two detections are in different locations should be taken as a source of doubt that a real object exists. The fact that four observations show no such object are yet more indication that there's no real object.

I suspect that if they created a Monte Carlo model of spurious detections, the possible reality of this "thing" would disappear like smoke. Moreover, I suspect that they detected it and not many more of them in other places of the sky precisely because they were looking at Alpha Centauri, and if they look at lots of other locations and cherry pick noise, they'll find lots more.

Exactly. Indeed, on the same day this second paper was reported, making a very similar claim, but this time toward W Aql.

The serendipitous discovery of a possible new solar system object with ALMA
http://arxiv.org/abs/1512.02650

Yes, thanks a lot Emily for this much interesting article about WISE.
But they say also inside about their WISE methodology that "(...) As a result, the W3 and W4 bands may reach a solar companion at 1–2 MJup out to greater distances than W2, although only ∼20% of the sky was mapped twice in those bands at their full sensitivity, which is necessary for a survey based on parallactic motion."

Luhman only suggests that the constraints indicate that there "probably" isn't a brown dwarf in the outer solar system. I wouldn't interpret that as ruling it out. In the Scientific American article you linked, when Billings says it is ruled out, he seems to be repeating Clara Moskowitz's questionable interpretation of Luhman's findings, that they "ruled out" anything. In truth, Luhman simply didn't find evidence of a brown dwarf companion from his search, which is very different from determining that there can't be one.

I'm no expert in radio astronomy; I do think that Liseau et al. are trying really hard to see what they want to see, though. What they're looking at seems like it could be just about anything, anywhere, two different things, or even nothing.

This story reached the Washington Post:

https://www.washingtonpost.com/news/morning...omepage%2Fstory

Unfortunately, it seems to be a case of bad science reaching the public, rather than good.

I'm heartened to see two professional astronomers calling out (among other things) the same thing that I did: What they detected are "blips" – deviations from the background noise that can readily happen as a matter of chance. It's all a matter of SNR. Spurious signals with SNR of 3.6 can and must happen quite often in the pixels of a sky survey.

An enormously useful principle I learned from Kepler analysis: Three observations of a possible dynamic object moving in one-dimensional parameter space are vastly more compelling than two. Two blips in different locations might be a moving object – but they might be two blips. You have an unconstrained degree of freedom in the delta of time and – in this case – spatial location. If you had three detections, then that degree of freedom goes away. Then, it becomes really convincing if you see the object has the same rate of motions between detections 2 and 3 as it did between detections 1 and 2. (Or, for Kepler, the same time interval between detections 2 and 3 as between 1 and 2.) This enormously reduces the probability of random noise posing as detections of a real object. (If an object moving across a visual field covered a significant portion of an elliptical orbit – as if we were seeing on object in the Alpha Centauri system as opposed to in the solar system – then the deltas would not the same, and then you don't actually have a good constraint with only three observations, because an infinite number of elliptical orbits are possible. You'd need four or more observations.)

This case never should have been web-published (in this form) and it won't pass peer review. If they had two observations with an SNR of 20 or three with an SNR of 7, that would be compelling. Two with an SNR<4 is simply nothing. It's like finding a footprint in London and saying you've solved the Jack the Ripper case.

From the SciAm article:

Reminds me of the FTL neutrinos from last year.

Where does it say that? Table 1 shows S/N of 21.4 for one observation and 4.3 for the other.

My mistake; I was reading the delta flux.

S/N of 21.4 is indeed something rare. 4.3 isn't. So we have one observation that might be something real… But there are other explanations possible. Kepler had anomalies due to inconsistent performance of the electronics. So an S/N that was seemingly real would be reported when it was a miscalculation: The noise was actually much higher in certain situations than typical situations, so real S/N was much lower and therefore much more likely to happen by chance than originally calculated.

I can't assess ALMA's data pipeline performance, but what we have is one noteworthy observation. Whether that occurred in the instrument or with a real object in space, I can't say.

The difference I see is that whereas those were inherently implausible the ALMA observation is not. The paper makes it clear that there is a significant region of size-distance-temperature space that only ALMA can observe. There's nothing inherently implausible about objects populating that region.

True, it's plausible that a real object would show up like this. What's implausible, as Mike Brown noted, would be that one super-narrow FOV observation would just happen to turn one up near Alpha Centauri. It's either incredibly lucky (hard to believe) or the outer solar system has lots of previously-unknown big objects (impossible).

Stranger things have happened: what are the chances of a comet flying ~100,000 kilometers from Mars in a human lifetime? Yet just last year it actually happened, and with instruments able to observe it from both Earth and Mars! There are so many possible low probability events and coincidences, they happen all the time. Though I agree it's still too early to be certain what ALMA found.

how many chances Galileo Galilei had to see Neptune, while he was in conjunction with Jupiter? Everything is possible ... then its proximity to Alpha Centauri would have masked WISE ... we can not rule anything!

Yes, events occur despite the fact that the probability of the event, as calculated after the fact, was very low. But there's a critical difference between saying so first and after the fact.

And science is not new to this idea. A good methodology is to create a Monte Carlo model of possible explanations and see which one is most likely given the observation. There are many explanations that could, in principle, explain this data. But the burden is on the researcher to vet the possibilities carefully, not just mention one or two theoretically possible explanations.

"the burden is on the researcher to vet the possibilities carefully, not just mention one or two theoretically possible explanations. "

The intent of the paper, as I understood it, was that after compensating for likely errors in the data, they felt like they may have found something they couldn't further explain, and wanted further investigation and input by others. In other words, they were already out of other ideas they were willing to put forth.

The title of the paper states: "ALMA discovers the most distant object of the solar system."

That's quite different from saying they had an observation they couldn't explain further.

I have my personal perspective on this since my work is not like physics or astronomy, where others can attempt to duplicate my result in the lab - or repeat the observation with their own instrument for verification. So I need hundreds if not several thousands of datapoints/observations to make a claim about anything, so that peer reviewers will not tear my paper to very small pieces - then jump up and down on the shreds with contempt.

Now that observations with ALMA submillimeter range falls more or less in the same exclusive category, since its the only radio observatory of its kind.
They need a little few more repeated observations over quite some time to make any claim to a discovery of anything.
My guess is that they did indeed observe something, at least for the observation of higher strength of signal, but that it was a transient phenomena quite further away in their line of sight and not anything comparatively local.

JRehling has already made most of the points I had upon hearing this story. But I would add a couple of comments.

First, it is astonishing that we didn't see a simple sanity check. Planetary astronomers must have crude, order-of-magnitude estimates of the number density vs size and distance for outer solar system bodies. Of course these will be largely model-driven and likely uncertain by orders of magnitude. But if those number densities implied the odds of finding such an object given ALMA's sensitivity and sky area mapped was between, eg, 1:100 000 and 1:10 000 000, then we could move on to other possibilities such as instrumental artifacts. There are quotes floating around from Mike Brown suggesting this is indeed the case, but I haven't seen any actual numbers.

Even more astonishing is that we only have two"blips" each (some with questionable S/N), ie one (perhaps) velocity each, as many have pointed out. At least for the alpha Cen case, it seems that this matter could have been trivially resolved by simply making another observation next observing season. The proper motion (if real) is such that the object should still be near alpha Cen in 2016. Is there some reason that this can't be done?

Tough crowd. And I must have missed the memo that said peer review could be done over Twitter.

The system will sort this out. I don't think you want to introduce a chilling effect where interesting results, even if premature, can't be put out on arxiv. The authors are taking chances of being criticized, but those are their chances to take.

It is true that many implausible things happen; not so much that anything is possible, but that extremely implausible things remain possible. But that doesn't mean we have to accept all claims with equal credulity.

Suppose that the kind of thing the paper claims to discover is a real kind of thing. Let's suppose there is exactly one such thing. There are a few chances in a billion that a specific ALMA aim contains said object. Maybe a few chances in a million that a similarly sensitive ALMA observation contains it (yes, that's purely speculative, but generous, I think). On the other hand, assuming the errors in the ALMA data are exactly Gaussian[*], there's about one chance in 13 of a >4 sigma false positive per observation[**]. So, even if a thing like they propose really exists, the chances are >>1,000,000 to 1 that a specific 4-sigma detection is a false positive.

OK, suppose there are 1000 such things, all staying just under WISE detectability (in itself, somewhat contrived and unlikely). Even if that is true, there is still a >>1000:1 preponderance of false positives.

There's a reason for peer review. And there's a reason you don't claim a discovery just because you can fit a line to two points. You need to try that third point before you've tested a hypothesis. Otherwise you reduce yourself to arguing about your idea of implausible vs. mine, or non-Gaussian statistics, or whether the instrumental effects are handled right in the 99.99th percentile cases, or coincidence of different objects, etc.

Of course, if we crank our supposition up to hundreds of thousands of real such objects, the report borders on plausible; but Mike Brown says we are all dead then, so we likely shouldn't be arguing over such worldly matters.

[*] If the instrument were a megapixel CCD detector of visible light, a SNR>20:1 false positive would not be a big surprise, given terrestrial radiation, cosmic rays and such. Many measurements have distinctly non-guassian tails to their errors.

[**] They indicate about 50x50 resolution elements, or 2,500 measurements, per FOV in the paper; a >4-sigma positive outlier is expected around 1 per 32,000 measurements.

If you're referring to the several tweets Brown made over a span of a half hour, I don't think they were comments that came from any serious work or thought; he seemed to be just tweeting his immediate reaction, crunching a few rough numbers so he could include a figure in his tweets. The tweets are quoted on the first page of this thread. Checking now, he responded on Twitter to a question about where the 200,000 figure came from, with https://twitter.com/plutokiller/status/676182202368045057
His response to the person who asked how it would kill everyone was the tweet: https://twitter.com/plutokiller/status/675472733271035905

I don't share the tendency of many to use how 'lucky' something would have to have been as an argument against it, but I'd think that recognition of that should be enough to cause one to look back over one's findings and verify that the data strongly support a claim before making it, particularly when the claim is as absolute as "ALMA discovers the most distant object of the solar system".

If you find a footprint that was made in a random London basement over 100 years ago, it might be Jack the Ripper's footprint, but the extreme improbability of that is a reason not to say that the footprint solves the Jack the Ripper case.

It's perfectly fine to say that it's a footprint and start to figure out whose it might have been. And that just might end up solving the Jack the Ripper case, but that's a claim to make much, much later in the process, not at the start.

If it's detectable now (and of sufficient magnitude) it should be hiding somewhere in Gaia's heaps of current data. Probably in the part scheduled for processed release in 2022...

I don't know how that's supposed to relate to what I wrote.

I said I don't use how 'lucky' something would have to have been as an argument against it. That doesn't mean I think every random, baseless proposition is true. In your Jack the Ripper footprint scenario, you have no reason to think it's his in the first place; that's the argument against saying it's his. How 'lucky' you'd have to be doesn't factor into it. Amend the scenario to have countless pieces of evidence in the basement, all strongly suggesting the footprint belongs to Jack the Ripper, and you'd probably rethink the notion that the 'luck' you would have to have to stumble upon Jack the Ripper's footprint is a reason not to say that the footprint is his.

The same thing would happen to your scenario if, instead of additional evidence, there were only two people who ever lived in London, one of the two was Jack the Ripper, and London itself consisted only of 2 basements. You wouldn't have to be very 'lucky' at all in that situation; in fact, you have a ~50% chance of any given footprint being his. That's still not a valid argument for or against it actually being his. Even in this scenario, you don't have any reason to claim that it's his. The requisite 'luck' changed drastically between the two scenarios, but the basis for such a claim is exactly the same as the original scenario; there isn't one.

If requisite 'luck' is an argument against things, then we should all be very skeptical of lottery winners.

We can talk about two possibilities for the alpha Cen observation:

1.) They caught a distant solar system body in two positions. The likelihood can be estimated as I wrote before given the estimated number density of bodies. There are indications from Brown that this is extremely unlikely (though we haven't seen all the numbers).

2.) They caught a transient on some distant stellar or galactic source, or some instrumental glitch, for the high S/N detection, plus a noise fluctuation for the low S/N observation. The odds for this are unclear, but likely not negligible, especially for a new instrument.

If actual quantitative estimates give a tiny probability for 1.) but order 50%, say, for 2.), then that tells you clearly which possibility is most likely. This is how we can say how "lucky" something is can be an argument against it. The key is that you have an alternative that is likely. This is done all the time in science: there often are alternative explanations to observations that can be discounted as extremely unlikely relative to other explanations. I see an elephant unlike any seen before in the wild. Far more likely that it's a one-off mutant than a member of a previously unseen new species.

A Bayesian outlook is quite compatible with lottery winners--if there is sufficiently good evidence they won the lottery. But if someone asks for a check but only proves they match the first 2 numbers, you should be skeptical. A SNR~4 observation still leaves false positive as the most likely explanation. A very high confidence observation still leaves coincidence of different objects as a more likely explanation, when fitting a line to only 2 points. Sure, reality will not bend to conform to the most likely explanation; but the most likely explanation will be right a lot more often than highly unlikely ones. So 'lucky' shouldn't be used to cross something off the list of competing hypotheses. But it very well should be considered, and balanced with how 'lucky' you'd have to be to get the observation from other hypotheses, if you're in the business of making predictions (i.e., science) or announcing shocking discoveries. Another couple observations in the band capable of SNR>20, and the discussion of how 'lucky' they were would fall by the wayside. But it is very, very relevant now, because 'noise' wouldn't have to be nearly so lucky.

Tentative planetary orbital constraints of some scenarios for the possible new Solar System object recently discovered with ALMA

I think this explanation is one of the most consistent ...

Abstract of the Alpha Centauri paper now reads:



Under comments: withdrawn until further data is available