Mapping the Heavens: The Radical Scientific Ideas That Reveal the Cosmos by Priyamvada Natarajan

Author:Priyamvada Natarajan [Natarajan, Priyamvada]
Language: eng
Format: azw3, pdf
Publisher: Yale University Press
Published: 2016-04-28T04:00:00+00:00

The fates of the universe in various cosmological models, showing how future and past behavior depend entirely on the values of cosmological parameter omega.

From just one measurement of the rate of change of the expansion of the universe, astronomers could determine which solution best describes our universe and therefore, by proxy, also determine its matter content and shape. Prior to the 1980s, it became clear that there was dark matter in galaxies and most likely also smeared in the spaces between them. Subsequently, as previously discussed, the matter inventory appeared to contribute to an omega equal to 0.3. Could the cosmological constant, lambda, then be equal to 0.7? There was only way to settle the matter—get more data, extend Hubble’s diagram, and check for any changes in the expansion rate of the universe in the past.

Looking for supernovae became one of the key agenda items for the Berkeley Center for Particle Astrophysics after it received NSF funding in 1988. The center’s primary focus, though, was dark matter, but it also worked to determine the full inventory of matter in the universe. Using supernovae as standard candles, its researchers investigated which of the solutions to Einstein’s equations would best describe the fate of our universe—the Big Crunch, the Big Chill, or Goldilocks. Supernovae searches were not new and had continued since Zwicky’s time, but it was clear that a team would need a smart observing strategy to discover large batches of them strewn about in the universe and catch them as they were exploding and at their brightest. The theoretically calculated rate suggests that we can expect one supernova to go off every hundred years or so in a galaxy. The only way to witness a large number of supernovae, then, is to observe as many galaxies as possible. Berkeley team members Saul Perlmutter and Carl Pennypacker, who were not trained astronomers, imagined that this question might take no more than a couple of years to settle. They planned to make use of automated observing techniques that Stirling Colgate had developed at Los Alamos National Laboratory in the 1970s. Colgate, an heir to the toothpaste fortune and a colorful character, was a creative and distinguished nuclear physicist. In the mid-1970s, he set up a thirty-inch telescope in the New Mexico desert and programmed it to look at a different galaxy every three to ten seconds. Automated observing with telescopes was starting to become standard then, but he pioneered this combination of automated repetition and searches for transient supernovae. An astronomer in search of supernovae would need to compare images of the same galaxy several weeks apart to see if a new bright flash of light had emerged. The brightness of a supernova is so immense that it can easily outshine its entire galaxy. With a clever strategy but a tiny field of view with his automated telescope, Colgate was not spectacularly successful in hunting down supernovae.

What Perlmutter and others distilled from Colgate’s experience was that the area of sky that needed

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