Kyle’s notes 9/09/08
HISTORICAL OVERVIEW OF TECHNOLOGY IN ASTRONOMY
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
Computation:
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