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24
Studying the Sun
| Question | Answer |
|---|---|
| Astronomers are in the business of | gathering and studying light. |
| The vast majority of our information about the universe is obtained from | the study of the light emitted from the stars and other bodies in space. |
| What type of waves are included in electromagnetic radiation? | Includes gamma rays, x-rays, ultraviolet rays, visible light, infrared radiation, microwaves, and radio waves. |
| What is electromagnetic spectrum? | The arrangement of electromagnetic radiation waves according to their wavelengths and frequencies. |
| All energy, regardless of wavelength, travels through the vacuum of space at | the speed of light, or 300,000 kilometers per second. |
| What are the two ways that light can be described? | waves and particles |
| What is the property of wavelength? | the distance from one wave crest to the next. |
| What is visible light? | The narrow band of electromagnetic radiation we can see. |
| Visible light consists of? | a range of waves with various wavelengths. |
| What are photons? | sometimes, light acts as this, a stream of particles |
| Photons | can be thought of as extremely small bullets fired from a machine gun. They can push on matter. The force they exert is called radiation pressure. |
| Each photon has | a specific amount of energy, which is related to its wavelength. Shorter wavelengths have more energetic photons. |
| Who discovered the field of spectroscopy? | Sir Isaac Newton |
| What is spectroscopy? | The study of the properties of light that depend on wavelength. |
| What is continuous Spectrum? | Produced by a incandescent solid, liqid, or gas under high pressure. Consists of an uninterrupted band of color. |
| Absorption Spectrum | Produced when visible light is passed through a relatively cool gas under low pressure. The gas absorbs selected wavelengths of light. So the spectrum appears continuous, but with a series f dark lines running through it. |
| Emission Spectrum | Produced by a hot gas under low pressure. It is a series of bright lines of particular wavelengths, depending on the gas that produces them. |
| The spectra of most stars are of the dark line, or | absorption type. |
| What is the Doppler Effect? | The perceived change in wavelength of a wave that is emitted from a source that is moving away or toward an object. |
| How is the Doppler Effect used in astronomy? | It is used to determine whether a star or other body in space is moving away from or toward Earth. |
| Larger Doppler shifts indicate _________________; smaller Doppler shifts indicate ___________________. | higher speeds; slower speeds |
| How are Doppler shifts measured? | Generally measured from the dark lines in the spectra of stars by comparing them with a standard spectrum produced in the laboratory. |
| Optical telescopes | Example is a Keck Telescope. Used to create an image that is a great distance away, a telescope must collect as much light as possible. Optical telescopes contain mirrors, lenses or both. |
| Refracting Telescope | Uses a lens to bend or refract light.The most important lens in this telescope is the objective lens. It produces an image by bending light from a distant object so that the light converges at a area called the focus. |
| Focus | Central point |
| Focal length of a lens | The distance between the focus (where the image appears) and the lens. |
| Eyepiece | a second lens used to examine an image directly. The eyepiece magnifies the image produced by the objective lens. |
| The _____________ ________ produces a very small, bright image of an object, and the ____________________ enlarges the image so details can be seen. | objective lens, eyepiece |
| What is the defect of refracting telescopes? | As light passes through any lens, the shorter wavelengths of light are bent more than the longer wavelengths. Consequently, when a refracting telescope is in focus for red light, blue and violet light are out of focus. |
| Chromatic aberration | Weakens the image and produces a halo of color around it. When blue light is in focus, a reddish halo appears. When red light is in focus, a bluish halo appears. |
| How can you reduce the chromatic aberration? | Reduced by using a second lens made of a different type of glass. |
| Reflecting telescopes | Invented by Newton to eliminate chromatic aberration. Uses concave mirrorthat focuses the light in front of a mirror, rather than behind it, like a lens. |
| What are the advantages of reflecting telescopes? | Light does not pass through a mirror so the glass for a reflecting telescope does not have to be of optical quality. Mirrors can be fully supported from behind. |
| What are the disadvantages of reflecting telescopes? | The secondary mirror blocks some light entering the telescope. |
| What are the three properties of reflecting and refracting telescopes that aid astronomers in their work? | light-gathering power resolving power magnifying power |
| Light gathering power | Refers to the telescopes ability to intercept more light from distant objects, thereby producing brighter images. Telescopes with larger lenses or mirrors "see" farther into space than do those with small ones. |
| Resolving power | Allows for sharper images and finer detail. |
| Magnifying power | The ability to make an object larger. Magnification is calculated by dividing the focal length of the objective by the focal length of the eyepiece. Thus the magnification of a telescope can be changed simply by changing the eyepiece, |
| What is the main material of which stars are made? | Hydrogen |
| Radio telescopes | Big dishes that detect radio waves. Focuses the incoming radio waves on an antenna, which absorbs and transmits these waves to an amplifier, just like a radio antenna. |
| What are the advantages of radio telescopes over optical telescopes? | They are much less affected by turbulence in the atmosphere, clouds and weather. No protective dome is required.Viewing is possible 24 hours a day. Radio telescopes can see through interstellar clouds. Can detect clouds of gases too cool to emit light. |
| What are the disadvantages of radio telescopes? | Hindered by human-made radio interference. |
| Space telescopes | Orbit above Earth's atmosphere and thus produce clearer images than Earth-based telescopes. |
| Hubble space telescope | First space telescope built by NASA. Provided images that clearly resolve the separation between Pluto and its moon. Provided data about planets that orbit other stars, the birth of stars, black holes, the age of the universe and the expansion of the un |
| Chandra X-ray observatory | Space telescope launched in 1999. Used to gather data about black holes. |
| Compton Gamma-ray observatory | used to study both visible light and gamma rays |
| The sun is | the earth's primary source of energy. |
| Why is the sun important to astronomers? | it is the only star whose surface we can study. |
| What is the sun made up of? | gas; no sharp boundaries exist between its various layers. |
| What are the four parts of the sun? | The solar interior The visible surface (photosphere) Two atmospheric layers The chromosphere and corona |
| Photosphere | light ball; radiates most of the sunlight we see and can be thought of as the visible "surface" of the sun. |
| What is the photosphere made up of ? | Consists of a layer of gas less than 500 kilometers thick. |
| What are the photospheres granuales? | Grainy, numerous small markings called granules. Granules are each the size of Texas. Their brightness is from hotter gases rising from below. As this gas spreads, cooling causes it to darken and sink back into the interior. Each granule survives 10-2 |
| Convection | The up and down movement of gas. Causes the grainy appearance of the photosphere and responsible for the transfer of energy in the uppermost part of the sun's interior. |
| Chromosphere | Just above the photosphere. A relatively thin layer of hot gases a few thousand kilometers thick. |
| What is the chromosphere made up of? | Consists of hot, incandescent gases under low pressure. It produces an emissions spectrum that is nearly the reverse of the absorption spectrum of the photosphere. |
| What makes the chromosphere's red color? | One of the bright lines of hydrogen contributes a good portion of its total light and accounts for the sphere's red color. |
| Corona | The outermost portion of the solar atmosphere. Is very weak and, as with the chromosphere, is visible only when the brilliant photosphere is covered. |
| What is the Corona made up of? | The outer fringe of the corona, Ionized gases, extends a million kilometers from the sun and produces a glow about half as bright as the moon. |
| The solar wind | The streams of protons and electrons that boil from the corona. This wind travels outward through the solar system at speeds up to 800 kilometers per second. |
| What is the temperature of the photosphere? | 6000 K. |
| Is the temperature at the top of the corona higher or lower than the photosphere? | The temperature unexpectedly increases upward from the photosphere, exceeding 1 million K at the top of the corona. Although the corona temperature is much higher that that of the photosphere, it radiates much less energy because of its very low density. |
| Why do sunspots appear dark? | Because fof their temperature, which is about 1500 k less than that of the surrounding solar surface. |
| What are sunspots? | The dark regions on the surface of the photosphere. An individual spot contains a black center rimmed by a lighter region. |
| What are Prominences? | Huge, cloud-like structures consisting of chromospheric gases.They appear as great arches that extend way into the corona. They are ionized gases trapped by magnetic fields that extend from regions of intense solar activity. |
| What are soar flares? | The most explosive events associated with sunspots. Brief outbursts that normally last about an hour and appear as a sudden brightening of the region above a sunspot cluster. They are relatively rare. |
| What happens during solar flares? | The release enormous amounts of energy, much of it in the form of ultra violet, radio, X-ray radiation. |
| What are auroras? | Also called the northern and southern lights, the most spectacular effect of solar flares. Earth's upper atmosphere near its magnetic poles is set aglow for several nights. |
| Can the solar interior be observed directly? | No |
| How does the sun produce energy? | By nuclear fusion |
| What is nuclear fusion? | A nuclear reaction that converts four hydrogen nuclei into the nucleus of a helium atom. Tremendous energy is released. Energy is released because some matter is actually converted to energy. |
| What happens during the process of nuclear fusion? | Only a small percentage of hydrogen in the nuclear reaction is actually converted to energy. The sun is consuming as estimated 600 million tons of hydrogen each second; about 4 million tons are converted into energy. As hydrogen is consumed, the product |
| Which type of radiation has the shortest wavelength? | gamma rays |
| The energy of a photon is related to its | wavelength |
| As light passes through a prism, which color will bend the most? Red, yellow, violet, blue? | violet |
| What type of telescope uses a concave mirror? | Reflecting telescopes |
| The thin, red rim seen around the sun during a total solar eclipse is the | Chromosphere |
| What is the source of the sun's energy? | Nuclear fussion |
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jclicurse
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