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rfmcdonaldIn his post "Van De Kamp's Planets" at Passing Strangeness, ![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
pauldrye takes a look at Dutch-American astronomer Piet Van De Kamp's disproved, but important, claims to discover a planetary system orbiting the nearby red dwarf Barnard's Star. Instrument error was key to the story.
Van de Kamp's legacy is complex. He inspired a lot of interest in Barnard's Star, in science fiction (for example, the novel Rocheworld's close-orbiting superjovian Gargantua) and in future plans for science (British Interplanetary Society's Project Daedalus proposal for an unmanned interstellar probe). More importantly, Van de Kamp's claims legitmized the idea of extrasolar planets. By his time, astronomers believed that there were planets orbiting the binary star 61 Cygni (1942) and the further 70 Ophiuchi (1943), the latter believed to host a planet even in the late 19th century. These planets were massive, superjovians bordering on brown dwarfs, but they were believed to exist for decades. This is important since previous theories had planetary systems be rare, our system of worlds formed by streams of gas thrown into space by a passing star. If three nearby stars had substantial planetary systems, the old model of planetary system formation which would make planets rare would be disproved.
The observations of Van de Kamp and others were wrong. The first actually existing planetary was found by a Canadian team in 1988 using an early version of the radial velocity method, Gamma Cephei Ab, just a few years before Van de Kamp's death. Still, despite his initial mistake and his refusal to admit said, he helped keep a dream alive and shift astronomy closer towards being a science accurately describing the universe. We owe him thanks.
pauldrye takes a look at Dutch-American astronomer Piet Van De Kamp's disproved, but important, claims to discover a planetary system orbiting the nearby red dwarf Barnard's Star. Instrument error was key to the story.[Van de Kamp] began his observations shortly after moving to Sproul in the spring of 1937, and kept them up for 26 years before announcing that he had in fact discovered a planet around Barnard’s Star. By his calculation it was about 60% bigger than the planet Jupiter, and it orbited the star at a distance of 4.4 AU (a bit shy of Jupiter’s distance from our own Sun). His discovery made quite a splash, as being the first to see an extra-solar planet (even indirectly) was a major coup. Other scientists had a hard time duplicating his results, but this was no great surprise: it relied on the Sproul Observatory’s 24-inch refractor, a kind of photographic telescope that was being mothballed in other observatories in favour of spectroscopic ones; furthermore van de Kamp had needed more than two decades of observations to be sure. It was going to take time for anyone else to check his results.
The first sign of trouble came after van de Kamp announced planets around other stars too: Epsilon Eridani, 61 Cygni, and one he’d mooted back in 1951, Lalande 21185. Another astronomer, Bob Harrington, noticed that the shape of the planetary wobbles was the same for all three, and for Barnard’s Star too—as if it were the photographic plates that were moving, not the stars. That turned out to be the case. When it was first made the Sproul Observatory telescope van de Kamp was using had had one of its lenses inserted the wrong way, and while the effect on its operation was very small, in 1949 it had been removed and reset the proper way. The slight change in the lens had made a slight change in the way light focused on photographic plates taken with the telescope, and by bad luck the change was about the same size as what van de Kamp had been expecting to see from his planets. He agreed that all of his data prior to 1950 was now suspect, but still argued that everything taken since then still supported his discovery.
With the idea of instrument error now in the open, though, another astronomer by the name of George Gatewood published a paper in 1973 which demolished van de Kamp’s planets. The consensus is now that there was a cycle causing the image of the stars to move, but that it was down here on Earth. The telescope underwent regular maintenance, and every time it did its focus shifted ever so slightly and made any star it observed appear to have moved. Ironically, Gatewood eventually changed his mind about one of van de Kamp’s claims, Lalande 21185, but this too has turned out to be instrument error
Van de Kamp's legacy is complex. He inspired a lot of interest in Barnard's Star, in science fiction (for example, the novel Rocheworld's close-orbiting superjovian Gargantua) and in future plans for science (British Interplanetary Society's Project Daedalus proposal for an unmanned interstellar probe). More importantly, Van de Kamp's claims legitmized the idea of extrasolar planets. By his time, astronomers believed that there were planets orbiting the binary star 61 Cygni (1942) and the further 70 Ophiuchi (1943), the latter believed to host a planet even in the late 19th century. These planets were massive, superjovians bordering on brown dwarfs, but they were believed to exist for decades. This is important since previous theories had planetary systems be rare, our system of worlds formed by streams of gas thrown into space by a passing star. If three nearby stars had substantial planetary systems, the old model of planetary system formation which would make planets rare would be disproved.
The observations of Van de Kamp and others were wrong. The first actually existing planetary was found by a Canadian team in 1988 using an early version of the radial velocity method, Gamma Cephei Ab, just a few years before Van de Kamp's death. Still, despite his initial mistake and his refusal to admit said, he helped keep a dream alive and shift astronomy closer towards being a science accurately describing the universe. We owe him thanks.
