Telescope (continued)
Modern astronomers essentially never use large telescopes for
real-time, visual observations in the manner of the astronomers
of previous centuries. Instead, researchers use telescopes to
record volumes of data for future study and computer-driven
analysis. Light received from most astronomical objects is made
up of radiation of all wavelengths. The spectral characteristics
of this radiation may be extracted by special instruments called
spectrographs. Standard, solid-state detectors called charge-
coupled devices (CCDs) or other imaging devices are used in
conjunction with spectrographs to record spectral information.
Photometry carried out with different filters yields basic infor-
mation about the source with shorter observing time than that
required for a complete spectroscopic analysis.
The Earth's atmosphere limits the effectiveness of larger tele-
scopes through image scintillation and motion, collectively
known as poor seeing. However, adaptive optics allow ground-
based telescopes to overcome blurriness and distortion caused
by the atmospheric turbulence (Fig. 3). Techniques of interfer-
+
ward
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science
Fig. 2 A depiction of Galileo demonstrating the use of a telescope to a crowd in
the 17th century.
(Credit: Getty Images)
Fig. 1 Multi-wavelength study of the core of the galaxy NGC
1512, revealing pockets of new star formation in both dust-
obscured and clear regions. The Hubble Space Telescope
obtained images of the galactic center in seven different
wavelengths, from the ultraviolet to the infrared, shown
in the boxes surrounding the centered, composite image.
Wavelengths invisible to the human eye are assigned a
representative color. These wavelengths are, clockwise from
bottom left: 220 nm (ultraviolet); 328 nm (ultraviolet); 545
nm (visible); 659 nm (visible); 827 nm (infrared); 1600 nm
(infrared); and 1870 nm (infrared).
[Credit: NASA, ESA, Dan Maoz (Tel-Aviv University, Israel,
and Columbia University, USA)]
Fig. 3 At the European Southern Observatory's Very Large Telescope (VLT) in Chile, one
of the four 8.2-m unit telescopes beams a high-powered laser as part of its adaptive optics
system.
[Credit: ESO/A. Ghizzi Panizza (www.albertoghizzipanizza.com)]