“Dreams of Other Worlds”: Hipparcos and Spitzer #WSW2013

Houston, we have lift off!

All week long for World Space Week, we will be posting exclusive excerpts from Chris Impey and Holly Henry’s new book, Dreams of Other Worlds: The Amazing Story of Unmanned Space Exploration. Each day will include an excerpt from a different chapter(s) about a different unmanned spacecraft, along with a picture of the craft that doubles as an iPhone background!

Today we have two excerpts. The first is from Chapter 8, which talks about the first star charts, which were created by the Greek astronomer, Hipparchus (for whom the Hipparcos was named). The second excerpt is from Chapter 9, explaining some of the adversities Spitzer had to face before it was able to go into space.

Tomorrow will bring another chapter and another adventure, so stay tuned!

HipparcosFor thousands of years, all we’ve known of Hipparchus’s star guide were descriptions by Ptolemy. But astronomer Bradley Schaefer asserts that, indeed, the Farnese Atlas, a statue of the Greek figure Atlas kneeling while holding on his shoulders a globe of constellations, represents the stars and constellations known to the ancient Greeks. He contends that the statue “is the oldest surviving depiction of the set of the original Western constellations, and as such can be a valuable resource for studying their early development.”18 Schaefer realized after a detailed study of the globe that the constellations depicted match the night sky in the era and from the location where Hipparchus lived in 129 BC. As evidence in favor of this possibility, Schaefer writes: “First, the constellation symbols and relations are identical with those of Hipparchus and are greatly different from all other known ancient sources. Second, the date of the original observations is 125 ± 55 BC, a range that includes the date of Hipparchus’s star catalogue (c. 129 BC) but excludes the dates of other known plausible sources.” Schaefer concludes that “the ultimate source of the position information [of the constellations on the globe] used by the original Greek sculptor was Hipparchus’s data.”

SpitzerSpitzer, from its earliest inception, was especially designed for infrared astronomy and is sensitive enough to detect infrared signatures of stars and galaxies billions of light-years away. The space telescope has been instrumental in unveiling small, dim objects like dwarf stars and exoplanets and can even determine the temperature of their slender atmospheres. Originally proposed in the late 1970s as NASA’s Space Infrared Telescope Facility, the Spitzer Space Telescope suffered from uncertainty, a delay after the loss of the space shuttle Challenger, near-cancellation, congressional limbo, budget cuts, and “descoping.” Nevertheless, in 2003 the telescope was finally launched, after being renamed subsequent to a public opinion poll conducted by NASA. The last of NASA’s four Great Observatories, the $800 million telescope was named after Lyman Spitzer, an early advocate of the importance of orbital telescopes.13 After launch, the spacecraft took about 40 days to cool to its operating temperature of 5 Kelvin. Once cooled, it took just an ounce of liquid helium per day to maintain its detectors at their operating temperature. A solar panel facing the Sun serves to gather power and protect the telescope from radiation.

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