Posts Tagged ‘Eclipse’

Ten Random Astromony Questions

January 21, 2010 Leave a comment

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.

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.

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.

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).

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.

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.

Solar and Lunar Eclipses

October 19, 2009 Leave a comment

There are many celestial events that happen daily. Most of these pass by without the slightest notice by the population at large, but only a few are talked about, prepared for, and celebrated. Many people across the world, however, recognize the phenomenon known as an eclipse. People will travel from country to country in order to view this celestial event. There are two categories of eclipse: solar and lunar.

A solar eclipse occurs when the moon passes between the Sun and the Earth. The Sun then becomes either partially or full covered to those viewing the eclipse on the Earth. There are several types of solar eclipses. The first is a total eclipse which occurs when the sun is completely obscured by the moon and the bright sun is replaced by the silhouette of the moon and only the corona is visible to the Earth. This type of eclipse is only visible on a very small section of the Earth.

The next type of solar eclipse is called an annular eclipse. This occurs when the Sun and Moon are exactly in line, but the moon appears to be much smaller than the Sun. Therefore, the sun appears as a very bright ring around the silhouette of the moon called an annulus. A hybrid eclipse occurs when the phenomenon phases between a total and an annular eclipse. The final type of solar eclipse is a partial eclipse. In this eclipse, the Moon only partially obscures the sun. This occurs because the umbra, or the darkest part of the shadow, never passes across the surface of the earth.

The other category of eclipse is called a lunar eclipse. This phenomenon occurs when the Earth passes between the Sun and the Moon causing the moon to dim proportionately the amount of light from the Sun that is blocked by the Earth. As with the solar eclipse, there are several different types of lunar eclipse.

The first kind of lunar eclipse is called a penumbral eclipse. This occurs when the moon enters completely into the Earth’s penumbral shadow. This type of eclipse is subtle and difficult to observe. The next type is called a partial lunar eclipse. This can be observed when the moon passes through the Earth’s umbral shadow. This is easily observable even to the naked eye. The third basic lunar eclipse is called a total lunar eclipse. This occurs when the entire moon passes through the Earth’s numeral shadow. This is a striking event due to the moon’s vibrant red color during the total phase.

The eclipse has been heralded throughout history by many different cultures as signs of good fortune or impending doom. Whether or not these phenomena actually mark the passing of significant events, eclipses will continue to captivate the Earth’s population at large for as long as humanity continues to exist on this planet.


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