Replies

Oddly enough, the Chicxulub crater was discovered about 1960, and something similar to the Alvarez theory was suggested in 1970 (and that may not have been the first, for all I know). The K-T boundary impact first came to the forefront circa 1980 (perhaps it was 1978?), and the candidate crater was suggested to the elder Alvarez by one of the Pemex guys involved in the 1960 study. He heard nothing back, and it was some years before Chicxulub was recognized as the smoking gun.

Nemesis, the Sun's companion star, 1983-present
The Nine Planets
"Hypothetical Planets"
This hypothetical "death companion" of the Sun was suggested in 1985 by Daniel P. Whitmire and John J. Matese, Univ of Southern Louisiana. It has even received a name: Nemesis. One awkward fact of the Nemesis hypothesis is that there is no evidence whatever of a companion star of the Sun. It need not be very bright or very massive, a star much smaller and dimmer than the Sun would suffice, even a brown or a black dwarf (a planet-like body insufficiently massive to start "burning hydrogen" like a star). It is possible that this star already exists in one of the catalogues of dim stars without anyone having noted something peculiar, namely the enormous apparent motion of that star against the background of more distant stars (i.e. its parallax). If it should be found, few will doubt that it is the primary cause of periodic mass extinctions on Earth...However, since the examination of the entire sky in the far IR by IRAS with no "Nemesis" found, the existence of "Nemesis" is not very likely.

[Raup originally proposed the idea in a 1984 with University of Chicago colleague Dr. J. John Sepkoski]

I think this Muller guy is the one quoted in the recent article (beats me where the magazine is, maybe in my car?) -- and says that, give him a million dollars, and he'll find Nemesis. He also has some thresholds for certain observations which will rule it out.

Nemesis: Does the Sun Have a 'Companion'?
by Robert Roy Britt
03 April 2001
Richard A. Muller... a physicist at University of California at Berkeley... [has] ideas... generally rooted in solid science and genius extrapolation... But Muller's biggest idea is a real Nemesis. Or so he claims. Like a thorn in the side of mainstream researchers, Muller's Nemesis theory -- that our Sun has a companion star responsible for recurring episodes of wholesale death and destruction here on Earth -- seems to reemerge periodically like microbes after a mass extinction. It's a theory that has many detractors. And it's a theory that has been beaten down and left for dead in the minds of most scientists... Muller's idea for Nemesis came to him 1983. Luis Alvarez, then an emeritus professor of physics at the University of California at Berkeley, and his son Walter had recently put forth the theory that a giant impact had wiped out the dinosaurs... Around the same time, two other researchers had suggested yet another controversial idea, that mass extinctions occurred at regular intervals -- every 26 million years or so. Scientists immediately folded the ideas into a new and breathtaking possibility: Impacts by space rocks were causing massive global species destruction every 26 million years.

AFAIC, periodicity in impact-caused extinctions are just a way to make catastrophe behave itself by being less random and more predictable. It's possible that the Sun has a companion, but if so, such a massive quasi-planet would have swept the outer solar system clear of debris a very long time ago.

from Raup's The Nemesis Affair (1986):

Unlike the paleontological record, the [geomagnetic] reversal record is fairly clean, at least for the past 165 million years of geologic time. About 300 complete reversals have been found in this interval, most well dated. There are smoe very long-term trends in the number of reversals per million years, and these have been known and accepted for many years -- even though there are no good explanations for them... I was encouraged to find a recent paper claiming periodicity in the number of reversals through time... J.G. Negi and R.K. Tiwari... concluded that there is a 32-million-year periodicity... a French group, headed by A. Mazaud, claimed a 15-million-year periodicity positioned in time such that every other pulse was a bit stronger and fell approximately at one of our extinctions... On the other hand, the problem had been looked at by a number of other geophysicists over the years... They had been unable to reject a hypothesis of randomness... I found an impressive 30-million-year periodicity that matched the extinction periodicity fairly well... Nature... neither accepted nor rejected the paper but returned it to me (with the reviews) to revise and resubmit. At the same time, I was invited to suggest the names of six additional reviewers. [pp 183-185]
Dr. David Raup
interviewed by Steve Brusatte
Dino Land Paleontology
1997
For a while, I thought mass extinctions were merely instances of chance coincidence of independent species extinctions. That clearly was wrong... I have come to the view that large-body impact is responsible for far more extinctions that we appreciate -- perhaps including those pulses of extinction that usually define stratigraphic stages. Maybe even zones? ...For periodic extinction, I know of 13 complete re-analyses of the Sepkoski data that have been published by independent investigators. Of these, five found our periodicity to be significant whereas eight found no significant periodicity. Had these studies used the new genus-level data, I suspect periodicity would have fared better. In any event, the periodicity of extinction must, I think, remain an open question until we have either more data or data of a completely different kind... I believe they really are periodic but I cannot prove it. One problem is that in time-series analysis, one can establish a departure from randomness rather easily but proving a particular periodicity within that is nearly impossible... The extinction record has been analyzed about as thoroughly as possible and searches for Nemesis have failed to find the companion star... I think periodicity is on the back burner but not forgotten -- any more than continental drift was forgotten.