Sun's Dark Companion 'Nemesis' Not So Likely

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."

Comments

Re:How long since last time

[cduffy]

Read the Fine Article.

We've got lots of time -- we're only 11 million years into this cycle.

Re:How long since last time

[vakuona]

"Fine". Seriously!? And here I thought it was...

Re:Second comment debunks

[Randle_Revar]

that's the third comment.

Here is a bit from the second comment:

The fact is that with modern and better paleontological data any peridocity is rejected, as easily checked with autocorrelation [Alroy, 2008]:

"Quantitatively, extinction rates in the Fossil Record 2 family data (3) and Sepkoski’s family and genus data (1, 2) are not correlated with themselves at any time lag (49), which is a necessary condition for periodicity to hold. That said, analyses of origination rates in all three datasets (49, 50) suggest short-term autocorrelation. However, the current dataset shows no autocorrelation in either kind of rate (Fig. S1), and a standard spectral analysis (Fig. S2) also suggests purely random variation through the time series (i.e., white noise)."

Debunked nicely in the comments

[wealthychef]

Read the comment "Bad research, worse article" in the comments section. "Melott has made an arxiv carrier of various kinds of pattern searches and catastrophism scenarios in data. (What I would like to call "pseudoscience conspirationism".) " To sum it up, this article is probably sensationalist psuedoscience and there is nothing to see here.

Re:Second comment debunks

[mrsquid0]

The preprint has been peer reviewed and has been accepted for publication in Monthly Notices of the Royal Astronomical Society, one of the most prestigious astrophysics journals on this planet.

Re:There is worse...

[openfrog]

Some more debunking in the second comment:

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; (...) [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.]

Re:period of passing through the galaxy ecliptics?

[sunspot42]

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, possibly due to the Oort Cloud experiencing some lag in reversing direction relative to the rest of the system. The sun essentially winds up off-center in the Oort Cloud, and in comparison to normal periods a lot of comets get kicked into the inner solar system as a result of this imbalance.

Re:I am doubtful

[sunspot42]

Check out the Wikipedia article on the Oort Cloud. The Oort Cloud is thought to be well over a light year across. Out on its fringes the influence of the sun's gravity isn't much stronger than the pull of nearby stars, or the galactic core itself. So whenever the oscillation reverses direction and the sun begins moving back toward the galactic plane, a lot of stuff out on the fringes doesn't move neatly with it. Some of it will become gravitationally unbound from the solar system, but some of it will find its orbit perturbed and start heading inward. Whether that's enough stuff to lead to mass extinctions here on Earth is another matter.

This article mentions disk tides, encountered most strongly as the Sol system passes thru the galactic plane, as the possible culprit in disturbing the Oort Cloud on a regular basis:

http://www.americanscientist.org/issues/pub/perturbing-the-oort-cloud

Re:11 million years

[gentlemen_loser]

Well, average life-expectancy of a species is 5-million years. Homo Sapience has already doubled that putting us at the extreme end of the scale that gives this average.

How are you doing your math? The genetic evidence shows that Homo Sapiens can be traced back 200,000 years. Nowhere near the 5 million you are stating as an average for species longevity. If you are counting Australopithecus anamensis, that would get you back to 4 million years, but I would hardly consider it to be the same species as us.

Furthermore, the actual average longevity of a species is 1 million years, not 5 (as evidenced here. Just because 10 million years appears to be an extreme upper limit does not make the average 5 million.

TFA doesn't think this is it either

[sean.peters]

Evidently the motion of the sun through the arms doesn't have the correct periodicity.