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

period of passing through the galaxy ecliptics?

[Kvasio]

isn't this the most simple explaination? Most stars in Mily Way arms are known to bounce up and down the ecliptic.

Re:How long since last time

[cheesee]

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.

BadAstronomer said something similar

[magsol]

...only it was a larger multiple: somewhere in the vicinity of every 150-180 million years. However, in this case, it's due to our solar system's z-axis oscillation with respect to the rest of the Milky Way galaxy. The dust and gas of the galaxy acts as a shield against cosmic radiation, but every 150-180 million years, our solar system reaches the z-edge of the galaxy and is maximally exposed to the elements.

What accounts for the 5-7 other mass extinctions within that time frame, however, I defer to TFA.