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Ten Random Astromony Questions
1. What are the steps in the scientific method?
The scientific method is the method used to explore observations and answer questions within the scientific community. It is a step by step process that has evolved since the earliest days of the analysis of observation. The first step in the scientific method is to ask a question about something that is observed. After a question is proposed, one must research in order to find the most appropriate process to find the answer and to ensure that mistakes that have been documented in the past are not repeated. Next, the researcher must propose a hypothesis, which is an educated guess constructed as an if-then statement, which can be easily measured and interpreted. Then the researcher must plan and implement a scientific experiment in order to test the hypothesis. After the experiment is concluded, the researcher must interpret the measurements and draw conclusions which either support or oppose the hypothesis. If the hypothesis is proven false, a new hypothesis must be formulated and the process continues from there; however, if the hypothesis is supported and methods are repeatable, the researcher must communicate his results to be verified by the rest of the scientific community.
http://www.sciencebuddies.org/science-fair-projects/project_scientific_method.shtml
2. How is a light year defined?
A light year a unit a measure used in astronomy due to the vast distances between astronomical bodies. Our Sun, for example, is approximately 150 million km away from the Earth. It is impractical to define such large distances by miles or kilometers, so scientists developed several different units of measure for astronomy. One such measure is the light year. It is defined as the distance that light travels in one year. Light travels at 300,000 kilometers per second. So in a year, light travels 9,460,800,000,000 kilometers. What this means for astronomers is that if a star is 100 light years away, the light that we are seeing from the star represents what the star looked like 100 years ago not what it looks like at the present time.
http://www.howstuffworks.com/question94.htm
3. Describe what happens during the two kinds of eclipses?
There are two categories of eclipses. These are solar and lunar. In a solar eclipse the moon passes directly between the Sun and the Earth obstructing the path of the Sun’s light to the Earth. Whether or not the viewer sees a partial or total eclipse depends on what part of the moon’s shadow falls on the Earth. The total eclipse in only visible in the umbra and this part of the shadow is very small on the Earth. A partial eclipse is observable in the penumbral shadow which covers a larger part of the Earth’s surface. The second eclipse category is called a lunar eclipse. This phenomenon occurs when the Earth passes between the Sun and the Moon during a full moon and the moon passes with in the umbral shadow of the Earth.
http://www.mreclipse.com/Special/SEprimer.html
http://www.mreclipse.com/Special/LEprimer.html
4. What is surface gravity?
Surface gravity is defined as the gravitational acceleration on the surface of an astronomical object such as a planet or a star. It is measured in units of acceleration, which is meters per second squared. Each astronomical body has a unique surface gravity which is determined by the product of the gravitational constant, G, and the mass of the object divided by radius of the object squared. The relative surface gravity of the Earth is 9.81 m/s squared. This means, that the gravitational pull of Earth exerts enough force to pull every object that is caught in its gravitational field toward itself at a speed of 9.81 m/s squared. Further, two objects that are accelerating toward the Earth’s surface will do so at this speed barring any outside interference. This outside interference is measured by multiplying the gravitational constant or G. For example, an F-16 fighter can withstand up to nine Gs. Within the equation, the number nine becomes the coefficient to measure the final modified surface gravity when taking into account the outside interference.
5. What is the difference between reflecting and refracting telescopes?
Every optic telescope falls in to one of two classifications, either refracting or reflecting. The telescopes are classified according to the method that they use to focus the image into the viewing device. A refracting telescope uses lenses to gather and focus light, while a reflecting telescope uses a mirror. The refractor telescope gathers a greater amount of light into the lens than is possible to gather with the naked eye. This presents the observer with a brighter, clearer, and magnified image of the object being observed. This is accomplished by focusing the parallel light onto a focal point while the peripheral light is focused onto a focal plane. A reflecting telescope uses a combination of curved mirrors that reflect light and form an image into a viewing device. A curved primary mirror is the basic optical element and creates an image at the focal plane. A viewing device such as film or a digital sensor may be located at the focal plane to record the image or an eyepiece might be present for viewing the image. The mirror in most modern telescopes is composed of solid glass that has been ground into a parabolic or spherical shape with a thin layer of aluminum deposited on the front which provides a highly reflective metal surface to reflect the images. The light from the image enters the end of the tube and reflects off the primary mirror, to the secondary mirror, and finally to the viewing device. Reflectors are not only useful for measuring visible light, but they can also detect shorter and longer wavelengths (e.g. ultraviolet and infrared light).
http://abyss.uoregon.edu/~js/glossary/reflecting_telescope.html
6. What are the Oort cloud and Kuiper Belt?
The Kuiper belt is a disk shaped region of icy debris about 30-50 AU from the Sun, which is outside the orbit of Neptune. It is similar in organization to the asteroid belt although it is far larger being 20 times as wide and 20-200 times as massive. Although similar in organization, the make up of the individual bodies is markedly different. The asteroid belt is similar to terrestrial planets being made mostly of rock and metal while the Kuiper Belt Objects (KBOs) share a similarity with the Jovian planets being made principally of frozen volatiles such as methane, ammonia, and water. The Kuiper belt is also the home of the dwarf planets Pluto, Haumea, and Makemake. Another organized structure of astronomical bodies has been theorized to exist called the Oort cloud, named for Jan Oort who originally theorized its existence in 1950. Light is so scarce in the far reaches of the proposed solar system that it is extremely difficult to identify the existence the cloud. The main evidence for the belt is the passage of long-period comets that pass through the inner solar system only once. The Oort cloud is home to astronomical bodies that vary in size from 50km to the size of Pluto. It has been theorized that there might be larger bodies within the Oort cloud as well, but no conclusive proof has yet been presented to confirm or deny this presumption.
http://solarsystem.nasa.gov/planets/profile.cfm?Object=OortCloud
7. What are the advantages of a telescope in space?
The main advantage of using a telescope that is based in space rather than on Earth is simply that the space telescope does not have to compete with the Earth’s atmosphere for light. The Earth’s atmosphere can distort the imaging ability of the earthbound telescope. It also blocks x-ray and infrared light so that those spectrums cannot be studied from Earth. Also, a telescope based in space does not have to deal with light pollution as do observatories on Earth.
8. What is a dwarf planet?
A dwarf planed it s a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape, has not cleared the neighborhood around its orbit, and is not a satellite. The classification was created for objects that are not quite large enough to be considered planets, but are larger than asteroids. There are currently five celestial bodies that are defined as dwarf planets.
9. What is meant by the resolution of a telescope?
The resolution of a telescope is defined as how clearly a telescope is able to view objects. The higher resolution yields a better ability to make out fine details in the celestial bodies being observed. Resolution is based highly on the quality of the optical components within the telescope, but the aperture, the hole that the light enters the telescope, of the telescope is also critical when dealing with resolution. For this reason, astronomers build bigger telescopes to allow more light in the aperture, increase the resolution, and create a finer more precise picture.
10. What is the difference between the geocentric and heliocentric model of the solar system?
The difference between the geocentric and heliocentric models of the universe hinges on Earth’s role in universal organization. The earliest thinkers believed that the Earth was the center of the universe and all things revolved around it, which was the central idea in the geocentric model of universal organization. This was refuted in 1530 when Copernicus presented a mathematical model in his book De Revolutionibus. Copernicus’ theory upset the religious order of the time so his work was refuted and suppressed, but eventually, with the invention of the telescope, Copernicus’ theory of the heliocentric model of universal organization became provable scientific fact.
Spectroscopy
A multitude of information can be and is gathered from the world, but oft overlooked is the one thing that gives this planet life. That is light, and more specifically light from the Sun. To many, when the Sun is viewed, this signals that it is time for the day to begin and for our work, school, or daily routine to commence. But what is the Sun made of? For that matter, what are stars made of in general?
This question began to be seriously considered and studied during the 19th century. Several scientists in the early 19th century began to contribute to early spectroscopy, which, historically, is the use of visible light dispersed according to its wavelength by a prism. This study led to the discovery by Charles Wheatstone that different metals could be easily distinguished by the different bright lines in the emission spectra of their sparks. This discovery launched the study of spectral analysis.
Diffusion of light
In 1854, a scientist named David Alter published an article that included the spectral radiance, which is the measurement that describes the amount of light that passes through or is emitted from a particular area and falls within a given angle in a specific direction, of twelve different metals. He went on to apply this in a later article to six different gases as well. This article contains a paragraph where he envisioned the application of spectrum analysis to astronomy in regards to the combustion of shooting stars or meteors.
Each element has a spectral fingerprint that is specific to that element. This is detected by analyzing either the emission or the absorption spectrum. The emission spectrum is used when the element being analyzed produces light, such as the spark from a combusting metal or a star. The absorption spectrum is the light that is left over after passing through a solid or gas. The cataloging of elements found on Earth has enabled scientists to analyze the spectral fingerprint of visible stars in our galaxy. This in turn, allows scientists to understand what elements make up specific stars.
Spectral analysis of our sun has yielded the elemental make up of our life-giving star. The sun, for the most part is hydrogen. In fact, it is 70% hydrogen by mass. The other main element found within the Sun is helium, which was actually discovered through spectral analysis of the sun prior to be found on Earth. The Sun is 28% helium by mass. 1% of the sun is oxygen and the remaining 0.5% contains other elements including, carbon, nitrogen, silicon, magnesium, neon, iron, and sulfur. The Sun is about 4.5 billion years old and still has about 5 billion years worth of hydrogen left to burn.
Without spectral analysis, it would be impossible to classify the elemental make up the Sun and many other stars that have been identified. This science’s impact has allowed humanity to better understand the similarities between the Sun and many other stars within our vast universe down to elemental composition.
References
http://chemistry.about.com/od/geochemistry/a/sunelements.htm
http://imagine.gsfc.nasa.gov/docs/science/how_l1/spectral_what.html
Comet Hyakutake
One of the most amazing celestial displays visible to the naked eye on Earth is the passing of a comet near our atmosphere. This event is rare, but spectacular when casual observers are able to view what is known as a great comet, which is a comet that becomes exceptionally bright and can easily be viewed through Earth’s atmosphere. 1996 was to be a special year for the viewing of a great comet. Comet Hale-Bopp was passing through the solar system and promised an amazing show, but unbeknownst to the astronomical world, 1996 would yield yet another great comet.
January 31st, 1996, amateur astronomer, Yuji Hyakutake, was looking into the night sky in search of comets. This had been Hyakutake’s practice for years. He had even moved to a rural southern Japanese province in order to better view the night sky. Using a powerful set of binoculars, Hyakutake had discovered a comet two weeks prior and was again scanning in a similar area in order to track the comet’s progress. While peering into the vast expanse, he noticed a new body. Hardly believing the discovery of a second comet, Hyakutake reported his discovery to the National Astronomical Observatory of Japan. This comet was later confirmed by independent observation later that day and dubbed Comet Hyakutake.
Comet Hyakutake
At the time of the comet’s discovery, Hyakutake’s magnitude, or brightness, was measured at 11.0 and the comet’s coma, or nebulous envelope around the nucleus of the comet, was measured at 2.5 arc minutes across. It was located 2.0 AU from the Sun. After the discovery, it was noted that the comet could be seen in photographs taken earlier when the comet was 2.4 AU from the Sun. Scientists noted that as Hyakutake passed near the Sun, it did not have a significant fading effect that is common to new comets as the layers of highly volatile materials evaporate due to the presence of the Sun. This led researchers to believe that this was not the comet’s maiden voyage through the solar system and perhaps the comet might yield a great show to those on Earth because more mature comets have a tendency to brighten instead of fade due to the lack of evaporation.
With the anticipation of Great Comet Hale-Bopp, Hyakutake was in danger of fading into obscurity, but the comet would have its day. Three days to be exact. The comet became visible to the naked in early March of 1996 and attained its full brightness on March 25, 1996. At its peak, observation estimated the comets magnitude at 0 and tail lengths of up to 80 degrees were reported as the comet passed within 0.1 AU of the Earth. Due to the small window of Hyakutake’s peak magnitude, it was unable to set the imaginations of humanity of fire as Hale-Bopp did the following year. However, the comet was greatly noted and admired.
Chemical analysis of the comet revealed that it was made primarily of ethane and methane. This was the first time that either of these gases had been detected in a comet. This led researchers to the conclusion that the comet was formed in interstellar space away from the Sun which would have evaporated the volatile gases. Spectrographic analysis of the comet’s ices determined the amount of deuterium, a stable isotope of hydrogen found abundantly in the oceans of Earth, present within the comet to be twice of what is found in Earth’s oceans. This study led to the possible debunking of the theory of Earth’s oceans being caused by cometary collision due the difference in deuterium levels. This finding was further confirmed by the analysis of Hale-Bopp and Halley’s Comet. The most surprising data garnered from Hyakutake’s passage was the revelation that the comet was emitting x-rays. This was the first observation of this phenomenon, but it was later confirmed by separate research that nearly every comet observed exhibited the same behavior. This phenomenon is thought to be caused by interactions between energetic solar wind particles and cometary material evaporating from the nucleus.
Comet Hyakutake’s Nucleus
Great Comet Hyakutake highlighted 1996 with an amazing celestial display, but not only was the show that the comet put on spectacular, but the new information regarding the make-up and emission properties of comets was just as spectacular to those within the scientific community. Although Hyakutake’s bright life span was short, it will continue to be one of the most celebrated cometary events of the last century and the data garnered from the study of this comet will continue to influence cometary research until such earthbound research is no longer necessary.
References
Reflecting Telescopes vs. Refracting Telescopes
Telescopes are the window to the universe. They allow the universe to be observed and studied from the vantage point of Earth. Without the amazing insight provided by these instruments, humanity would still be living in naivety of our place in the universe and the universal picture as a whole. Beginning in the 17th century, telescopes have provided great insight into the space around us and continue to provide amazing imagery and data that allow us to understand the universe as a whole in much more definite detail.
Every optic telescope falls in to one of two classifications, either refracting or reflecting. They are classified according to the method that is used to focus the image into the viewing device. A refracting telescope (refractor) uses lenses to gather and focus light, while a reflecting telescope (reflector) uses a mirror. The refractor telescope gathers a greater amount of light into the lens than is possible to gather with the naked eye. This presents the observer with a brighter, clearer, and magnified image of the object being observed. This is accomplished by focusing the parallel light onto a focal point while the peripheral light is focused onto a focal plane.
Refracting Telescope Optics
The refracting telescope was the first telescope to be invented and used. The first apparitions of the refractor telescope were created in the early 17th century. The inventor was a Dutch lens maker named Hans Lippershey who intended to use the device for military purposes. He applied for the patent for the refractor in 1608. Galileo was the first person credited with applying the use of the telescope to the study of the sky. With this, he was able to see the craters on the moon, the four major moons of Jupiter, and the rings of Saturn.
There are several problems with the refracting telescope. First and foremost, refractors lend themselves to what are called chromatic and spherical aberrations. Chromatic aberration occurs when a lens fails to focus all the color to the same focal point. This defect shows as a fringe of color along the boundaries that separate dark and bright parts of the image. This was dealt with originally by increasing the focal length of the lens which led to extremely long telescopes. Spherical aberration occurs due to the increased refraction of light rays when they strike a lens near its edge. This causes the outer rays of light to be focused more tightly away from the focal point which causes the image to be imperfect. Another issue with refracting telescopes is lens sagging. This occurs in telescopes with large lenses. This is a result of gravity deforming the glass since the lens can only be held in place on the edges. This also produces an imperfect image. Further, there is a problem with lenses themselves. Lenses are flawed with small air bubbles trapped within the glass, which is also opaque to certain wavelengths of light. Even visible light is dimmed by the reflection and absorption when the light passes through the glass.
Spherical Aberration
Due to the issues with the refracting telescope, ideas for developing a telescope that used curved mirrors instead lenses began to circulate in the 17th century. This idea had been introduced in the 11th century by Alhazen in his widely read work, Book of Optics. Although the idea had been present for several centuries, no practical application of the theory occurred until 1673 when Robert Hooke created the first working reflecting telescope. Isaac Newton has been credited with the creation of the first practical reflecting telescope using a spherically ground metal primary mirror and a small diagonal mirror. This design is now known as the Newtonian telescope, and is still popular for amateur telescope builders. Although the theoretical advantages of the reflector design compensated for many of the disadvantages of the refractor, it took over 100 years for the reflector to become popular due to the poor performance of speculum metal which was being used as the reflective surface at the time. With the perfection of parabolic mirror fabrication of the 18th century, silver coated mirrors of the 19th century, and long-lasting aluminum coated mirrors of the 20th century the reflecting mirror has become the telescope of choice for astronomers world-wide.
Reflecting Telescope Optics
A reflecting telescope uses a combination of curved mirrors that reflect light and form an image into a viewing device. A curved primary mirror is the basic optical element and creates an image at the focal plane. A viewing device such as film or a digital sensor may be located at the focal plane to record the image or an eyepiece might be present for viewing the image. The mirror in most modern telescopes is composed of solid glass that has been ground into a parabolic or spherical shape with a thin layer of aluminum deposited on the front which provides a highly reflective metal surface to reflect the images. The light from the image enters the end of the tube and reflects off the primary mirror, to the secondary mirror, and finally to the viewing device. Reflectors are not only useful for measuring visible light, but they can also detect shorter and longer wavelengths (e.g. ultraviolet and infrared light).
Mirrors within the reflecting telescope eliminate the risk of chromatic aberration, but this type of telescope may still produce other types of aberrations, namely spherical. This was the design flaw within the Hubble Space Telescope’s mirrors originally. There are other types of aberrations as well, but these have been corrected with more advance telescope design. The design most common in professional telescopes is the Ritchey-Chrétien telescope, which is a specialized Cassegrain telescope that utilizes two hyperbolic mirrors instead of a primary parabolic that is common in the standard Cassegrain design.
As technology continues to advance, the future for optics is bright. With further advance in the science of optics, we will continue to garner a greater understanding of the universal picture as a whole and where our place is within that ever expanding picture.
References
http://csep10.phys.utk.edu/astr162/lect/light/refracting.html
http://www.enchantedlearning.com/inventors/page/t/telescope.shtml
http://abyss.uoregon.edu/~js/glossary/reflecting_telescope.html
Bok Globules
The birth of a baby is one of the most amazing miracles to behold in the natural world. From conception to birth, the change that a baby endures beginning as a single cell and ending up as a full grown and functioning human being in the short span of forty weeks is unrivaled in nature. Stellar birth, however, is also an extremely amazing event. Although the birth of a star takes an eternity in comparison to the human gestational cycle, it is one of the most amazing processes that occur within the celestial realms. One place where the birth of stars occurs is within dark molecular clouds called Bok Globules.
A pair of Bok Globules
Bok globules are dark, dense clouds of dust and gas found within H II regions, which are low density clouds of gas and plasma that can be as big as several hundred light-years in diameter. These Bok globules typically have a mass that ranges between 0.1 and 2000 solar masses, a unit of astronomical mass measurement that is equal to the mass of the Sun. They are contained with an area of about a light year or so in diameter. Molecular hydrogen, carbon dioxide, helium, and a small percentage of silicate dust are found within these clouds.
These astronomical phenomena where first observed by astronomer Bart Bok in the 1940s. Bok and his researcher partner E.F. Reilly published a paper in 1947 that stated these clouds were similar to the cocoons of insects. They hypothesized that these clouds were undergoing gravitational collapse to form protostars from which star clusters and star systems were formed. This hypothesis was difficult to verify due to the fact that the clouds obscure all visible light being emitted from within the cloud. However, infrared analysis observations published in 1990 confirmed that stars were being formed within the Bok globules.
Bok globules are the smallest manifestations of dark nebulae, which are interstellar clouds that contain a very high concentration of dust that allows them to scatter and absorb visible light. Bok globules support both the inflow and outflow of material, a process common in the development of protostars. These clouds are known to have a temperature of around 10 Kelvin.
Bok globules are still being intensely researched and their inmost properties are still being analyzed. While there is still much information to be garnered from Bok globules, what is known is that they actually serve as a cocoon protecting infant protostars from being stripped by radioactive stellar winds from other nearby stars and the block all visible light. Bok globules are an amazing phenomena and the understanding of these clouds will give us an even greater insight into the birth of stars.
References
http://astronomy.swin.edu.au/cms/astro/cosmos/B/Bok+Globule
http://www.universetoday.com/2009/02/02/journey-inside-a-bok-globule/
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
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