Kyle’s notes 9/09/08 historical overview of technology in astronomy

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Kyle’s notes 9/09/08


Astronomy is often considered the oldest science (maybe not?). Technology has long been a critical ingredient to advances in this, like all, sciences.
Pre-telescope (before 1609)

Human eye as detector

Instruments included sighting markers or tubes and “glorified protractors”

(look for displays at Adler when we next visit)

1609!! First astronomical use of telescope (by Galileo) TECHNOLOGICAL REVOLUTION!

Gains: light-gathering; resolution; magnification

Discoveries: moons around Jupiter and phases of Venus (both recognized as evidence

for heliocentric picture of Solar System);

craters on Moon and sunspots (both evidence against some aspects of geocentric);

diffuse glow of Milky Way was really many faint stars

rest of 17th, 18th, and most of 19th centuries – no comparable technological revolutions

ever larger & better telescopes (mostly refractors, but occasionally a few reflectors)

more accurate scales attached to the scopes for better measurements

detector was still human eye

many discoveries as more people used larger telescopes…

late 19th century, continuing into 20th century 2 MAJOR NEW TECHNOLOGIES

spectroscopy: attaching simple prism spectrograph to back of telescope showed dark (absorption) lines in solar spectrum and then in spectra of stars; stellar spectra were NOT all alike (some resembled the Sun, most did not); some diffuse nebulae showed emission lines

spectroscopy eventually resulted in temperature, chemical composition, radial velocity measurements for stars (Yerkes as “first astrophysical observatory”) Better spectrographs as progress continued

photography – first major new detector advance(direct photos through telescope and as detector on spectrograph)

advantages: permanent record; integration pushes to fainter limits

color differences between stars became much more obvious (early photos limited to blue)
20th Century
around 1900 also reflecting telescopes started coming into common use, thus larger sizes
Dominated by photography until ~1980s
1920s onward, photography on large reflectors resulted in discovery that many faint “nebulae” were other galaxies, and that they had radial velocities that increased with distance from us (expansion of universe) (key person: Hubble)
1920s-30s early electronic detectors and other instruments yielded better precision than photographic, but initial applications required large amounts of time on large telescopes to get this precision (measured 1 point at a time)

1950s saw enormous increase in electronic measurements of starlight as detectors and electronics improved greatly (early pioneers with local connections: Whitford, Johnson, G. Kron)

Large telescopes at national observatories starting in 1970s have meant that astronomers from all institutions can do research at a level previously open only to a few institutions that had the largest scopes (including large scopes in southern hemisphere)
1980s onward: CCDs became detectors of choice for nearly all optical observations (more sensitive than photography but 2-D imaging like a photo over a small area); now ubiquitous and sizes up to a couple of cm are cheap enough to be used by nearly everyone; images are digital, easily analyzed on computers, and easily copied for archiving and distribution (see below)

Outside the visible light window

first half of 20th century also saw first significant observations in near-IR and near-UV, but only slightly outside of visible wavelengths

1930s, but especially 1950s onward, radio astronomy opened first observational window well outside the visible spectrum, and thus many new discoveries

Observations above the ground

Rocket flights in 1950s and satellites from 60s onward opened UV, X-ray, gamma-ray, leading to explosion of discoveries

Spacecraft explored much of Solar System 1970s onward, men to the moon
HST 1990 and continuing: moderate size scope (2.5 m), but above the atmosphere, publicity concentrates on good resolution pix (but can now do better from ground using adaptive optics), UV advantage is unique to space

Ground-based IR (near-, and windows in mid-IR) opened with new detectors and electronics in 1960s, followed by airborne IR telescopes in 70s and onward, a few IR satellites 1970s onward


Pre-1950s all astronomical calculations by hand or mechanical desk calculators – limited both theory and observations (latter because measurements could not be analyzed as fully as might have been possible – in some cases observations were actually taken in less precise ways that would sacrifice some precision to make analysis far easier)

Some use of computers in a few big projects in 1950s

Computers became common at observatories and universities in 1960s, allowing more detailed theoretical calculations and better data analysis

Rapid major increases in computing power in recent decades such that common desktop and laptop computers of today can handle the calculations that required the largest computers of 2 decades ago

Internet allows easy distribution of data and software so students can now do the same type of data analysis (and theoretical calculations) as professional astronomers

21st Century
Surveys are growing in importance, may be the emphasis in astronomy research for next decade

SDSS as a pioneer – CCD imaging over ~25% of sky and spectroscopy of > million galaxies, stars, qsos… (~8 years and counting)

New larger surveys are in the works, with LSST within the next decade will image entire sky (as visible from Chile) down to very faint limits, and do this every few nights to find changes! There may not be many new discoveries for amateurs or students to make, but there will be enormous new opportunities for data-mining and follow-up.

Some surveys keep data proprietary for a period (1 year for SDSS) before public release, others (LSST) will release data to the public almost as quickly as it is taken
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