Download Thibou Page 1 of 6 Telescopic Analysis of Tomorrow: Advances in

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Telescopic Analysis of Tomorrow:
Advances in the Study of Distant Stars and Planets
Astronomy II: Stars: PHYS 1118-3450 Dec2012
by Ronald Thibou
Although the work of many individuals in the pre-telescope era, one of the latest of which was
Tycho Brache, was highly accurate in documenting the positions of the visible points of light in the sky,
the telescope significantly broadened the realm of astronomy. Before the invention of the telescope,
man relied on naked-eye analysis of the heavens for millennia (Anderson 22). But on November 30,
1609, Galileo Galilei changed all of that when he pointed his homemade telescope at the moon and
other parts of the sky from his Padua home and later documented his findings. The telescope was
probably invented earlier; the first person to attempt to patent it was Hans Lipperhey in 1608.
However, earlier uses were largely for terrestrial, oceanic, and war purposes. They were also less well
documented.
Galileo, documenting the uneven terrain of the Moon, the moons of Jupiter, the
appendages on the side of Saturn (now known to be rings), and sun spots is probably a significant father
to the telescope and modern astronomy (Schilling and Christensen 10-15).
Although Galileo’s small up to about 5cm (30x) refracting telescopes were quite functional, it
soon became apparent that bigger is better. We now know precisely that the brightness of an image is
directly related to the area of the collecting mechanism or the square of its diameter. Consequently, a 5
meter collector will be able to see an image 25 times dimmer than a 1 meter collector in the same
amount of time (Chaisson and McMillan 103). Additionally, the resolution is inversely related to the
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angular resolution/distance which is directly related to the wavelength of the light or electromagnetic
radiation divided by the diameter of the primary collecting mechanism. Therefore, a 5 meter collector
can resolve the same wavelength image 5 times better than a 1 meter collector (Andersen 45). Larger
lens tended to split light like a prism and blur the image. It was not until Isaac Newton improved the
design of the recently invented reflecting telescope in 1668 with his small 3.1 cm concave mirror
reflecting telescope that the theoretical foundation for increasingly larger collectors (in this case
mirrors) was developed (Schilling and Christensen 17).
Today many telescopes with large mirrors are in operation.
The current biggest optical
telescope depends on your definition of “biggest.” The current biggest single piece mirror telescopes
are the Subaru 8.3 meter telescope on Mauna Kea (8.2m of which is usable) and the four Very Large
Telescopes (VLT) (8.2 meters each) in Chile. However, the VLTs can be combined with interferometry to
the resolution equivalence of a mirror of greater than 130 meters and is by far the biggest “astronomy
machine” ever built. The Large Binocular Telescope in Arizona has two 8.4 meter mirrors with an
equivalent light collection of an 11.9 meter telescope and the interferometry resolution of a 22.8 meter
telescope. The current biggest mirror with multiple segments is the 10.4 meter Gran Telescopio
Canarias in Spain’s Canary Islands but it generally cannot use the whole mirror in practice (74.14m2
collecting area) (Schilling). The largest usable surface is on the two Keck 10 meter telescopes (76m2
collecting area each) in Mauna Kea which can also increase their resolution with interferometry to the
equivalent of a 85 meter telescope. The largest solar telescope is the National Solar Observatory’s
(NSO) 161cm McMath-Pierce Solar Telescope in Arizona (Schilling and Christensen 51-59).
In addition to optical telescopes, an increasing number of telescopes allow observers to see
electromagnetic radiation outside of the visible spectrum. Land based telescopes can view at least some
electromagnetic radiation in the radio, microwave-millimeter-infrared, and near ultraviolet regions.
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Cosmic radio waves were accidentally discovered in the 1930s. Radio telescope collectors do not have
to be as smooth as other wave detection mirrors since radio wavelengths are longer. However, since
the wavelength is longer, the resolution generally is not as good as optical telescopes. The largest
steerable single-dish radio telescope is the 100 meter Green Bank Telescope in West Virginia. The
largest full-dish telescope is the fixed 305 meter Arecibo radio telescope in Puerto Rico. Additionally,
arrays like the 27 antennae 25 meter antenna/telescope array in New Mexico called the Very Large
Array (VLA) use interferometry between numerous antennae to sharpen the image data. The largest
connected radio telescope is the LOFAR telescope with more basic antennae spread in clusters over 100
km within the Netherlands and over 1500 km throughout Europe. The largest dedicated (near) infrared
telescope is the 4.1 meter VISTA in Chile (ESO – VISTA). The largest sub-millimeter (far infrared and
microwave) telescope is the 15 meter James Clerk Maxwell Telescope in Mauna Kea. Cosmic gamma
rays cannot be directly detected on earth but the 2 Magic Telescopes on the Canary Islands and the 4
H.E.S.S.’s in Namibia can detect when the rays create elementary particles in the atmosphere
(Hofmann). Scientists are even attempting to detect gravitational radiation and waves at the Laser
Interferometer Gravitational Wave Observatory (LIGO) in Washington State and Louisiana (Andersen
177). Of course, the most productive current optical (and infrared and ultraviolet) space telescope is the
2.4 meter Hubble Space Telescope (Schilling and Christensen 81-94).
When presented in this way, one can almost guess where the future lies with telescopes. Bigger
mirrors, more wavelengths analyzed, better spectrographic and other analytic technologies, and more
space telescopes. The biggest observatory project currently underway is the probably the $1.5 billion
Atacama Large Millimeter Array (ALMA) in Chile. It will be the largest, most expensive, and highest
ground observatory ever built with 54 12-meter antennae and 12 7-meter antennae which can be
moved around 10 miles of desert 16,500 feet above sea level. This is much larger than the James Clerk
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Maxwell Telescope. The first image from only the partially constructed array in October 2011 was of
never before seen details of the colliding Antennae Galaxies 45 million light years away. The array
should be completed by March 2013. Millimeter and sub-millimeter wavelengths are useful in studying
the formation of the first galaxies and interstellar dust and gas in closer galaxies and the Milky Way
(Schilling and Christensen 84-85).
The most promising optical projects underway are probably the Thirty Meter Telescope in
Mauna Kea, the 21.4 meter Giant Magellan Telescope in Chile, and the 39.3 meter European Extremely
Large Telescope in Chile. These telescopes will probably be completed in the 2020’s. After this,
something along the lines of the recently cancelled 100 meter European Overwhelmingly Large
Telescope (OWL) will be attempted. While the technology exists to build the OWL today, the over $2
billion price tag was prohibitive. Of course, these telescopes will also rely on more advanced technology.
For example, a 10 meter telescope only needs one guide star laser for adaptive optics; a 40 meter scope
may require five. The proposed 8.4 meter Large Synoptic Survey Telescope (LSST) in Chile will be
outfitted with special CCDs that can accurately survey large portions of sky over time for movement or
brightness changes; this will help advance man’s quest to predict and address asteroid strikes among
other things with its completion scheduled for the 2020s (Andersen 202). Also the supercomputer that
translates the primitive radio data from LOFAR into an image may be upgraded and used for the Square
Kilometer Array in Australia or South Africa, which will have upgraded radio antennae, by the 2020’s to
construct the most sensitive radio telescope ever (Schilling and Christensen 110-119).
Finally space telescope advances are also planned. Hubble’s successor will likely be the 6.5
meter infrared James Webb Space Telescope (JWST) in about 2018. It will be useful in detecting the redshifted initially UV radiation of the first stars (Loeb 133). JWST is also considered a first generation
mission towards imaging exoplanets. Second generation Terrestrial Planet Finders (TPF) or Darwin
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arrays of 4 laser-interferometer connected space telescopes would attempt to detect nearby planetary
systems with relatively low quality spectra. Third generation Life Finders and Planet Imagers would
attempt to image exoplanets beyond point source views. This could require a mirror/collecting area of
500-5000m2 (Perryman 167)! Also being considered is a Solar Orbiter with an orbit half the distance
between the Sun and Mercury to study the physics of the sun including its coronal mass ejections and
magnetic fields (Alexander 202). This would likely be after the 2018 or so completion of the NSO’s
terrestrial solar telescope upgrade, the 4 meter Advanced Technology Solar Telescope (ATST) on Maui
(Schilling and Christensen 120-125).
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Works Cited
Alexander, David. The Sun. Santa Barbara, CA: Greenwood/ABC-CLIO, 2009. Print. Greenwood Guides to
the Universe.
Andersen, Geoff. The Telescope: Its History, Technology, and Future. Princeton, NJ: Princeton UP, 2007.
Print.
Chaisson, Eric, and Steve McMillan. Astronomy Today. 7th ed. Boston: Addison-Wesley, 2011. Print.
"ESO - Visible and Infrared Survey Telescope for Astronomy." ESO - Visible and Infrared Survey Telescope
for Astronomy. European Southern Observatory, 09 Dec. 2012. Web. 09 Dec. 2012.
<http://www.eso.org/public/teles-instr/surveytelescopes/vista.html>.
Hofmann, Werner. "The H.E.S.S. Telescopes." The High Energy Stereoscopic System. H.E.S.S.
Collaboration, July 2012. Web. 09 Dec. 2012. <http://www.mpihd.mpg.de/hfm/HESS/pages/about/telescopes/>.
Loeb, Abraham. How Did the First Stars and Galaxies Form? Princeton, NJ: Princeton UP, 2010. Print.
Perryman, Michael. The Exoplanet Handbook. Cambridge, UK: Cambridge UP, 2011. Print.
Schilling, Govert, and Lars Lindberg Christensen. Eyes on the Skies: 400 Years of Telescopic Discovery.
Weinheim: Wiley-VCH, 2009. Print.
Schilling, Govert. "The New Largest Telescope in the World." Sky and Telescope. N.p., 16 July 2007. Web.
09 Dec. 2012. <http://www.skyandtelescope.com/news/home/8530807.html>.