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Astronomy Unit 1A

by: Emily Mason

Astronomy Unit 1A Astronomy 1020

Emily Mason

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These notes cover the learning objectives presented in Unit 1A.
Stellar Astronomy
Dr. Flower
Study Guide
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This 6 page Study Guide was uploaded by Emily Mason on Wednesday January 13, 2016. The Study Guide belongs to Astronomy 1020 at Clemson University taught by Dr. Flower in Winter 2016. Since its upload, it has received 253 views.


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Date Created: 01/13/16
Unit 1A Learning Objectives: Science  Science- derives from the Latin scientia meaning to know. Science is a consistent body of knowledge about matter and energy, including the methods by which this knowledge is obtained and the criteria by which its truths are tested. o Science mainly relies on observations of nature, which are statements of high standards, composed in the precise language used in a particular science. o Examples: lead is 11.34 times denser than water, a lunar rock weighs 31.4 grams. o Observations of nature are obtained through experiments, observing, collecting, and cataloging. o Some sources of error involved in obtaining facts of nature are imperfections in instruments, human error, improper observational techniques, and poor observing conditions.  Scientific Method- a system of securing and testing scientific knowledge described in a series of steps. o Steps: 1. Gather information/Observations: Observers and experimentalists gather, process, and store observations of nature relevant to the problem they are investigating through experimenting, observing, collecting, and cataloging. 2. Explain information with a hypothesis: Experimentalists try to explain observed phenomena with a hypothesis 3. Test the hypothesis with experiments  Hypothesis- a preliminary explanation for a phenomenon that may or may not be supported by further observations or experiments. Uses human induction and data. o Induction- when our minds put together bits and pieces of information and uncover new lines of thought.  Theory- describes a hypothesis that has considerable experimental support. They are hypothesis that have been confirmed.  Scientific Laws- statements or mathematical relations founded on extensive observations of nature. These observations have clearly demonstrated that the scientific laws are always true, under certain conditions o Example: Boyle’s law states that the volume of a given amount of gas at a fixed temperature decreases as the pressure on it increases. This law applies under normal conditions on earth but may not on other planets.  Sources of error in astronomical observations: o Often, radical results, ones that question our fundamental theories and paradigms, are the result of experimental errors  Paradigms- it is basically an example, and consists of scientific laws, diagrams that give insight into the laws, and a group of calculations and solved problems that everyone agrees are done correctly.  In order from least certain to most certain: Hypotheses (least), Theories, Scientific Laws (most) Learning Objectives: Basic Electromagnetic Radiation  Electromagnetic Radiation- waves of a given wavelength (λ) with a certain energy traveling at the speed of light (c).  The more energy an electromagnetic wave has, the shorter the wavelength.  The approximate wavelength of red light is 780-622 nm (nanometers)  The approximate wavelength of blue light is 492-455 nm  One of the most important interactions in astronomy is between Electromagnetic Radiation (photons) and individual atoms.  This interaction is the absorption of photons by atoms. The atom absorbs the energy of the photon of EMR and this causes electrons in atoms to move further away from the nucleus of the atom into outer orbitals. (Remember it like this: absorption, away)  Emission – As the electron that has been removed from one orbital moves towards the center of another, it then emits and causes a photon to move further away from the nucleus of the atom into outer orbitals. Learning Objectives: Telescopes  Refraction- when light changes direction or bends o Results from a change in the speed of light as it passes from one medium to another o Refraction is used in telescopes because light passes through the lens, is refracted, and meets a point called the focus. This light then goes through a second lens called the eyepiece. The focal lens, or the distance between the center of the lens and the point where the spot of light is smallest, determines how much the telescope magnifies.  Reflection- when light bounces off a surface; the angle at which it bounces off is perpendicular to the surface the light strikes. o The curved nature of the lens made it able to also form a focus point. o Without alteration, this focus point is at an awkward location because it is nin the light path of the object being viewed.  Types of Telescopes 1. Galileo’s Telescope- uses a refracting lens 2. Prime Focus- blocks only a small fraction of light 3. Newton’s Telescope- The focus of the primary mirror is to the side of the telescope tube because he added a small flat secondary mirror to reflect light. 4. Cassegrain Telescope- brings the focus of the primary mirror to the rear of the telescope by reflecting light with a secondary mirror back through a hole made in the primary mirror. 5. Coude Telescope- moves the focus away from the telescope to anywhere in the observatory.  Magnification- the ratio of the focal length of the objective (lens at the front of the telescope) divided by the focal length of the eyepiece. In other words,  Resolving Power- one advantage over the eye/one of the main functions of a telescope that measure how well a telescope can distinguish between two objects close together or how much detail it can show of extended objects such as surfaces of planets  Light Gathering Ability- one advantage over the eye/another function of a telescope that refers to the capability of larger and larger telescopes to produce brighter and brighter images, allowing observers to see fainter objects.  The largest telescopes built in the last century and today are reflectors because they applied a thin layer of shiny metal to the surface of glass, which makes the mirrors extremely reflective, reflecting more than 90% of visible light. Also, the mirror itself can be glass or another ceramic, which does not have to be optically perfect since light never passes through it. They are easier to shape and are lighter than metal.  Atmospheric blurring- distortions in images caused by any misalignments in the telescope mirror and its supports and by atmospheric turbulence.  Active Optics- methods that adjust for mechanical and optical misalignments due to manufacturing errors in the shape of the mirror and to the stresses on the mirror when the telescope is in different positions. o First, it divides the image of a star into cells. If there were no distortion, the parts in image of each cell would be exactly centered. A computer then determines the necessary correction to the shape of the primary mirror to center the image in each cell.  Adaptive optics- a new technique that corrects in real time for blurring caused by atmospheric turbulence. o The system divides the light from a star into pieces. Lasers then excite atomic sodium, causing it to emit at a wavelength of 5890A. The sodium “star” then appears as a point of light and is high enough in the atmosphere to be above the distorting effects of the atmosphere.  Radio Telescopes- a parabolic dish that acts like the mirror of an optical telescope by focusing the radio waves from the sources it is pointed toward onto the dipole. The dipole at the focus produces electric currents, which receivers amplify and record. o A major disadvantage is their poor resolving ability, or the ability to separate two images.  Interferometry- the technique in which telescopes far apart synthesize a telescope with a diameter equal to the Earth’s diameter. Observers record the data from each telescope on magnetic tapes. Researchers then paly the tapes back into a computer that combines the signals as if they were from a single telescope.


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