Sun's Dark Companion 'Nemesis' Not So Likely 306
TravisTR passes along a story about the death of Nemesis. "The data that once suggested the Sun is orbited by a distant dark companion now raises even more questions... The periodicity [of mass extinctions] is a matter of some controversy among paleobiologists but there is a growing consensus that something of enormous destructive power happens every 26 or 27 million years. The question is what? ... another idea first put forward in the 1980s is that the Sun has a distant dark companion called Nemesis that sweeps through the Oort cloud every 27 million years or so, sending a deadly shower of comets our way. ... [Researchers] have brought together a massive set of extinction data from the last 500 million years, a period that is twice as long as anybody else has studied. And their analysis shows an excess of extinctions every 27 million years, with a confidence level of 99%. That's a clear, sharp signal over a huge length of time. At first glance, you'd think it clearly backs the idea that a distant dark object orbits the Sun every 27 million years. But ironically, the accuracy and regularity of these events is actually evidence against Nemesis' existence."
period of passing through the galaxy ecliptics? (Score:5, Interesting)
isn't this the most simple explaination? Most stars in Mily Way arms are known to bounce up and down the ecliptic.
Second comment debunks (Score:5, Interesting)
The second comment under the article seems to be a pretty serious debunking. I'm not going to take sides or tell you who's right and wrong because I don't know, but I will note that arXiv (the source for the claims) is for pre-prints and is not peer-reviewed.
Re:How long since last time (Score:5, Interesting)
From FTA:
There is a smidgeon of good news. The last extinction event in this chain happened 11 million years ago so, in theory at least, we have plenty of time to work out where the next catastrophe is coming from.
If you RTFA... :) (Score:1, Interesting)
You'd see this: "There is a smidgeon of good news. The last extinction event in this chain happened 11 million years ago so, in theory at least, we have plenty of time to work out where the next catastrophe is coming from."
Another thing to keep in mind - even if it's "dark" it will still have some non-zero temperature. So one of our long wavelength satellites (including the newest crop: Herschel, Planck, and WISE) would have or will eventually see it.
WISE, especially, according to projections based on pre-launch specs will be able to identify the following:
* Gliese 229B to 150 lightyears
* A brown dwarf warmer than 200 K to 4 lightyears
* A freefloating planet like Jupiter to 1 lightyear.
What happened to the theory about... (Score:1, Interesting)
The periodicity of the Solar system traveling parallel to the axis of the galactic center up and down through the arm of the galaxy. This, I thought, was close the the time frame for mass extinctions and was presumed that our traveling through the more cluttered parts of the arm were to blame for us coming in contact with debris.
Re:How long since last time (Score:5, Interesting)
Better still, read the comment to the article by Torbjorn at the same URL as the article. Torbjorn calls it "Bad research, worse article" and he makes a pretty strong case.
Re:period of passing through the galaxy ecliptics? (Score:1, Interesting)
This. The closer we get to the central plane, the more likely we are to hit awful periods of random rocks in space, and possibly exploding stars, that would be the worst, huge increase in cancer rates in most animals across the board.
Random stardust in general will be more prevalent up there too, leading to increased cosmic rays.
I, for one, will be building an underground city, you are welcome to join me Slashdot.
LifeVault 100, Ayrshire, Scotland, over and out.
BadAstronomer said something similar (Score:5, Interesting)
What accounts for the 5-7 other mass extinctions within that time frame, however, I defer to TFA.
Re:Second comment debunks (Score:2, Interesting)
I read the comment. It seems to be mostly composed of reused commentary from the articles in question, unsubstantiated (and grammatically nonsensical) personal attacks on the authors involved in those articles;
[Not to poison the well, but Bambach published lately in Ruse and Sepkoski eds "Paleontology at the High Table." One must take a dim view with the abilities of anyone that choose to cooperate with "philosopher of biology" and known stealth creationist Ruse.]
and very little information supporting the comment author's position other than what appears to be mostly speculative musing;
First off, there is likely no "growing consensus that something of enormous destructive power happens every 26 or 27 million years". It is an old idea, probably originated with the terrible paper by Raup and Sepkoski 1986, which I have criticized on the web several times; it defines peak in an ad hoc and inappropriate manner (as noise), claim to but doesn't really use a null hypothesis et cetera. That it would have growing support outside the community who looks for pattern identification in data I seriously doubt.
I did not find it a rational nor compelling rebuttal.
Re:Only one logical explanation: (Score:3, Interesting)
Re:period of passing through the galaxy ecliptics? (Score:5, Interesting)
No, the most simplest explanation is that it's all an imagined phenomenon. A statistical anomaly due to selection bias, miscalculation, or vastly incomplete data-set... A ghost. Occam's Razor says so.
I am doubtful (Score:1, Interesting)
Re:Debunked nicely in the comments (Score:3, Interesting)
Melott is a perfectly respectable palaeontologist ; Bambach I've read less of. But having RTFP [arxiv.org], I don't find it hugely convincing, nor hugely badly presented. Without spending a few days at least on reading up the background and working the statistics myself, I remain unconvinced in either way. (Which in no way reflects on Melott, Bambach, or Torbjorn Larsson.)
Executive summary : different workers can't agree on whether there is any significant periodicity to extinction events (that hasn't changed in the 25 years that I've been listening to this discussion) ; amongst those who think that there is a periodicity, there is only a weak majority putting the period at ~27Ma over those claiming ~11Ma or ~50Ma (another sign that the raw evidence isn't terribly strong).
Without even a good estimate of the periodicity (if there is one), then trying to work out the causative mechanism is resting a hypothesis on a house of cards built on a sand castle in the Bay of Fundy. Which might make an interesting spectator sport, but not a terribly successful career.
Re:period of passing through the galaxy ecliptics? (Score:5, Interesting)
The sun doesn't just orbit the center of the galaxy, though. It also moves up and down relative to the galactic plane. Some have suggested that whenever the solar system reverses direction in that oscillation, very bad things happen, ...
That's close to a conventional explanation, but off by 1/4 cycle. The extreme high/low points of the solar system's bobbing orbit are outside the galactic plane, and would be the low-danger points. The rough parts of the (approx. 60 million year) cycle are the two crossings through the central part of the galactic plane, which are the densest portions. During the crossings, the solar system is zipping through the galactic plane at a few hundred km/s, producing lots of collisions with whatever rubble happens to be there.
Part of the explanation from the astronomers who've done the studies is that, although we're about in the middle of the galactic plane right now, we're actually in a "Local Bubble" about 300 light years across, so there's not much galactic rubble in the solar system right now. There are low-density bubbles like this scattered around, the results of things like supernova explosions in the distant past.
Stick around for another million years or so, and we'll exit the local bubble. There might be some nice fireworks then, and perhaps another mass extinction.
Of course, we are going through a mass extinction event right now, but it's an unusual one with a known causative agent that's not astronomical. It seems that a new top-level predator has recently evolved, which has been devastating the ecosystem all over the planet. This will probably confuse the paleontologists in the future, since they'll see a mass extinction during a crossing of the galactic plane, but won't see any evidence at all of the impact that presumably caused it. They'll also see the evidence of a species with high intelligence, but of course that couldn't be the cause, because you wouldn't expect a highly-intelligent species to destroy its own ecosystem, right? So the extinction event will remain a mystery.