Tuesday, November 25, 2014

Science - Astronomy Tools

Science - Astronomy Tools
 
Astronomers use a wide variety of tools in order to observe and collect data. The electromagnetic spectrum provides the template to design and implement instrumentation for study, and lessons learned by other specialties have also been brought to bare on a variety of topics.
Astronomy is the study of everything - as coined by Carl Sagan, this includes understanding certain phenomenon here on Earth. Atmospheric studies and geography are examples. The list of specialties sometimes called on by astronomers include: meteorology, paleontology, biology, geography, seismology, physics, chemistry, quantum physics and computer science.
Meteorology and other atmospheric studies on Earthcan help us understand the atmospheres of Venus andMars, as well as understand the spectacular cloud formations on Jupiter and Saturn as well as Uranusand Neptune. With Saturn's moon Titan, the only moon in our solar system we know to have a substantial atmosphere, will help us understand our own primordial atmosphere.
Paleontology and the study of ancient rock structures here on Earth can help us understand the newly discovered nuances of rock formations and ancient riverbeds on Mars.
Biology combined with astronomy is a relatively new field called Astrobiology. The newly discovered extremophiles in our own deep oceans as well as the evidence of previous liquid water on Mars has allowed this subspecialty to grow. Combine this with the oceans under the icy sheet of Europa and the primordial atmosphere on Titan, and we have an exciting future.
Geography, the study of land mass formation and cratering, allow us to understand meteorite impactson the other planets and moons so we can better understand the evolution of the crust of the terrestrialplanets. By studying volcanism and plate tectonics, we gain knowledge of how volcanoes and land mass motions occur elsewhere.
Seismology is also a fairly new subspecialty in astronomy. Our Sun and other stars have demonstrated to seismic vibrations, and we are slowly beginning to understand what this means. Studying earthquake phenomenon here on Earth will help us understand this phenomenon elsewhere.
Physics is used heavily in astronomy. This allows us to understand the nature of light and gravity as well as orbital motion. Modified Newtonian physics have given rise to Einstein's Relativity as to the study of particle and wave nature of light.
Chemistry allows us to determine to chemical composition of space dust, stars, planets, and so forth. Variations of elements, called isotopes, can also help us create timelines of chemical evolutions ofstars and planets.
Quantum physics allows us to understand the fundamental particles and hopefully crack the mystery of Dark Matter - the 90% unknown composition of the Universe. Neutrinosand gamma ray particles also benefit from knowledge gained by quantum physics.
Computer science allows us to create programs run on clusters of computers to run simulations for analysis. Galaxy formation, stellar evolution, orbitaldynamics, and even Dark Matter simulations rely heavily on computers.
As you can see, there is a large pool of knowledge and experience that astronomers can draw from. The study of these specialties greatly enhance our knowledge of astronomical phenomenon and those results in turn enhance the subjects from which we draw.


Astronomy Tools - Concepts

As mentioned several times, astronomers use a wide variety of tools. Most of these tools are optical and electronic in nature and have been designed to visualize and interpret specific frequencies within theelectromagnetic spectrum. In addition, some novel methods have been designed to circumvent various initiations of examining specific frequencies within the spectrum.
Not all of the electromagnetic spectrum is available to study here on Earth, and some levels of our atmosphere offer some additional road-blocks for those frequencies that are accessible.
The following describe the electromagnetic spectrum and its limits here on Earth. By combining instrumentation both in space and on the surface, we are able to study the entire spectrum.

Concepts - The Electromagnetic Spectrum

The electromagnetic spectrum (also called the EM-band) contains gamma rays, radio waves and everything in between. The history of discovering the electromagnetic spectrum is a fascinating one. Sir Isaac Newton used a prism to split sunlight into its fundamental colors of the rainbow.
Sir William Herschel discovered, by accident, the infrared portion of the spectrum when he placed thermometers above the red portion of a projected spectrum. The image on the left shows how this was confirmed, with one of the three thermometers places above the red portion of the spectrum
Johann Ritter suspected "invisible" light on the opposite (blue) end of a spectrum and used paper soaked with silver chloride to detect it. Thomas Young confirmed the wave nature of light (that light moves like waves similar to ocean waves) by examining diffraction patterns through slits.
Michael Faraday and James Maxwell collaborated together to theorize the electromagnetic nature of light - that is changing the electric current in the wave alters its magnetic field. The image below (don't laugh, I'm still learning Adobe Illustrator!) demonstrates how the magnetic portion of this wave is 90o to the electric portion of the wave - hence 'electromagnetic.'

Experimenting with "Maxwellian Waves," Heinrich Hertz discovered radio waves. Wilhelm Rontgen discovered X-Rays while seemingly serendipitously experimenting with electric current through cardboard tubes with exposed film he had on the other end of the room - he saw the bones of his hand.
It wasn't until Albert Einstein, winning the Nobel Prize for discovering the photoelectric effect, that the wave-particle duality of electromagnetic waves was understood.
Eventually, a tool was created in the form of the electromagnetic spectrum.
As a starting point for understanding the spectrum, visible lightcovers only a small part - 400 nanometers (blue) to 700 nanometers (red).
The image below is a graph from the Chandra website demonstrating the entire electro-magnetic spectrum. Notice that only a very small portion of this spectrum (in the middle) is made up of visible light.

Concepts - Atmospheric Limitations

While the entire electromagnetic spectrum allows us to view phenomenon a variety of different ways, we are limited as to what we can see - at least on Earth. Our atmosphere is a life preserving blanket of protection from particles like microwave, high energy ultraviolet and gamma rays. However, at these frequencies we can learn a lot by studying phenomenon such as accretion disks aroundblack holes and quasars - and these are best "viewed" from space.The solution is to overcome the natural limitations of our atmosphereand place tools capable of viewing high energy phenomenon in orbit around the Earth, high above the atmosphere.
The image below demonstrates what we can see on Earth:
Only radio waves and the visible spectrum are viewable from the surface, however with a telescope on top of a high mountain (like the Keck Observatory on Mauna Kea, Hawaii) it is possible to view objects in the near-infrared.
Concepts - Space Observations

While radio waves, near-infrared (near-IR), and visible light are observable from surface of the Earth, we need to introduce tools into space to observe other frequencies of the EM-band.This section will introduce:
Near-IR
Infrared
X-Ray
Ultraviolet
Gamma Ray

Near-IR:
In order to see the small window of the near-IR spectrum from the ground, some novel approaches have been designed and implemented. Viewing of the near-IR is possible only by:
  • Very high altitude
  • Using super-cooled CCD imagery
  • Mirrors using silver or gold coated mirrors
  • Small secondary mirrors
  • Cooled telescope tubes and housings of mirrors along the optical path
An example of an infrared optimized telescope is the Keck Observatory Gemini-North telescope.
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Infrared:
To view the residual IR spectrum, high altitude observatories - or orbiting satellites - are required. Another method is to observe from Antarctica - if you like the cold!
There are two in-flight observatories:
In addition, the following observatories are (and were) in orbit around the Earth:
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X-Ray:
This high-energy portion of the EM-band is only visible from space. Between 1949 to 1962, sounding rockets traveling up to 100 km above the surface would carry Geiger counters to measure X-ray emission. A sounding rocket is nothing more than a standard rocket with the Geiger counter and other related electronics housed in within the nose.
By 1970, several orbiting X-ray observatories would begin capturing valuable data. These include the following observatories:
Objects observed by X-ray are (but not limited to) supernovaremnants, accretion disks, pulsars, and black holes.
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Ultraviolet:
The ultraviolet (UV) region of the EM-band allows the study of very hot, young stars. Additionally, populations of young, hot stars within the disks of spiral galaxies are within easy view of a UV telescope. This also requires satellite observatories. Here is a list of UV observatories:
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Gamma Rays:
Gamma rays are the highest energy radiation resulting in extremely short wavelengths. Sources of gamma rays are supernovas, neutronstars, intense gravity regions and active galaxies (galaxies with a large and active black hole at the center). Here is a list of some gamma ray satellites:
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