tss@astrovax.UUCP (Thomas S. Statler) (03/14/84)
Um, perhaps I can clear up a few things... The recent noise in the popular press about the 'Death Star' stems from a pair of papers recently submitted to Nature and circulated in preprint form. The existence of an unseen companion to the sun is suggested in "Extinction of Species by Periodic Comet Showers" by Marc Davis, Piet Hut, and Richard Muller. The companion paper, "Evidence in Crater Ages for Periodic Impacts on the Earth" by Walter Alvarez and Muller, discusses the supporting evidence. These papers probably would have gone unnoticed by the popular media if it were not for the fact that universities have public relations offices. Because the Davis, Hut, & Muller paper is highly speculative and deals with a 'sexy' topic, press releases were prepared by the Institute for Advanced Study (Hut's institution) and, presumably, by U.C. Berkeley (home of the others). Unfortunately, people who write such press releases rarely understand what they are writing about; the release from the IAS contained several errors, and the newspapers and TV stations added their usual amount of distortion. (The Daily Princetonian reported on page one that the object had been "discovered" by Hut and his col- leagues.) There is not a huge battle being waged in the scientific community over these papers, except perhaps between those who feel their pet theories are being threatened, and there has been no attempt to keep information from "J.Q. Public". My impression is that the idea is generally regarded as intriguing, but the probability of actually proving or disproving it is so vanishingly small that it will remain a matter of almost pure speculation for some time. On the other hand, the notion of finding a candidate object in, say, the IRAS data is not absurd. If the object is a Jupiter-sized body or a "brown dwarf" it would be expected to show up as warm object with a large proper motion (due mainly to parallax) between successive all-sky surveys. (By the way, Jupiter radiates quite a bit more than the terrestrial planets because its main energy source is gravitational contraction rather than radioactive decay.) PLEASE don't quote me on this, but there have been rumors that the IRAS people have candidates for very-outer solar system objects. There is NO indication as to what the mass of the object(s) (if any) might be, and there has been no further word from any of the IRAS investigators. In fact, forget I said anything. As for the crater data, I admit I have only skimmed the paper, but it appears to be an exercise in small-number statistics. After limiting their sample to craters older than 5 Myr and with uncertainties in their ages of < 20 Myr, Alvarez & Muller are left with only 13 craters. They claim to see 8 maxima over 225 Myr, so that the mean number of data points per peak is < 2. The minima are at zero amplitude. Again, I have not read the paper carefully, but I'm a bit skeptical. I hope I've managed to cure some of the confusion.