NAT SCI 13 - Astronomy Ancient to Modern Astronomy PDF

NAT SCI 13- ASTRONOMY Ancient to Modern Astronomy The Golden Age of Astronomy – Greece 600 BC to 150 AD The Ancients Ancient Mesopotamia ▪ The basics of geometry and tr...

NAT SCI 13- ASTRONOMY Ancient to Modern Astronomy The Golden Age of Astronomy – Greece 600 BC to 150 AD The Ancients Ancient Mesopotamia ▪ The basics of geometry and trigonometry helped them explain the motions of -Sumerians and Babylonians earliest planets, sun and moon However, they known civilizations to practice erroneously decided that everything in the astronomy. They developed detailed lunar calendars and were among the “heavens” revolved around the earth. That first to create star catalogs. is what appears to happen, but this apparent motion is really due to the earth’s -Their observations also contributed to early astrology, with the belief that rotation. They decided that the Earth celestial events could influence human couldn’t be rotating because we feel no affairs. motion. Ancient Egypt SOME OF THE FAMOUS GREEKS -Solar Worship- Ra (God of Sun). ARISTOTLE They used the heliacal rising of Sirius to mark the beginning of the Nile flood, knew that the earth was a sphere because a crucial event for agriculture. during an eclipse the earth’s shadow was a circle. However, Aristotle believed in an earth -Architectural Alignments: The centered (Geocentric) solar system. construction of pyramids and temples ARISTARCHUS often involved astronomical alignments. For example, the Great was the first to propose a sun-centered Pyramid of Giza is aligned with solar system (Heliocentric), but no one incredible precision to the cardinal agreed with him. Aristotle’s influence was too points strong and lasted over a thousand years. He also tried to calculate sizes of the moon and sun and distances to them. The ▪ Early Babylonians Egyptians and method was good, but his measurements Chinese made important astronomical were off, so his answers were wrong. observations ERATOSTHENES -calculated the ▪ The five closest planets were observed circumference of the earth. and novas and comets were recorded HIPPARCHUS -observed and recorded ▪ Comets were blamed for disasters and over 1,000 stars for his star catalog. These were seen as portents of doom measurements were later recorded by ▪ Calendars: Many ancient cultures Ptolemy. developed complex calendar systems based on astronomical observations, which were crucial for agricultural and ceremonial purposes. PTOLEMY -compiled a 13-volume book which TYCHO BRAHE explained the work of Greek Astronomers. In ▪ The Danish astronomer Brahe was a the dark ages to follow, these works were meticulous observer who made many preserved by Arab scholars. accurate measurements of the motions of heavenly objects. ▪ Telescopes were not yet invented and The problem he used devices called pointers to ▪ The Greeks believed that the planetary accurately line up stars to measure orbits were circles and that everything went them. Also, he did not believe in the around the earth, including the sun and heliocentric model due to what he saw planets, and the stars. as a lack of stellar parallax. ▪ The stars resided on a crystal sphere ▪ The concept of parallax shows that as through which light shown. Unfortunately you view an object from two different for the Greeks, the solar system was not positions it will appear to shift against that simple. They had trouble reconciling the background. this model with the observed motion of the planets. So, they tried changing things slightly JOHANNES KEPLER ▪ Kepler, an Austrian by birth, became THE PROBLEM WITH RETROGRADE Brahe’s assistant about a year before MOTION Brahe’s death ▪ Kepler, a brilliant mathematician, As planets revolve, they sometimes appear to analyzed Brahe’s 20 years of go backwards in their orbit. This is called astronomy data and discovered some retrograde motion. interesting relationships in the data. ▪ The Ptolemaic System- Ptolemy had KEPLER’S LAWS OF PLANETARY introduced the concept of epicycles. As MOTION a planet orbited the earth, it moved in small circles. These were called ▪ The 1st law states that planets travel in epicycles. elliptical orbits, rather than circular orbits. This eliminates the need for ▪ The middle ages were a time of those pesky epicycles scientific stagnation. ▪ The 2nd law states that a planet travels COPERNICUS faster closer to the sun, so that it covers Nicholas Copernicus, a Polish astronomer, equal triangle shaped orbit sections was the first great astronomer in a long time. during the same amounts of time. His revolutionary book was published as ▪ You probably noticed that the planets Copernicus was dying. He was afraid to travel at different speeds. The inner publish it because the Catholic Church, very planets travel more quickly than the powerful at the time, firmly believed in the outer planets Kepler’s 3rd law give a geocentric model, which put man in the center mathematical relationship for this. This of the known universe. relationship is: period(of revolution)^2 = -Giordano Bruno, who refused to deny the distance (from the sun to the planet)^3, heliocentric theory of Copernicus, was burned : p2=r3 at the stake in 1600. GALILEO GALILEI ▪ His law of Universal Gravitation ▪ one of the first scientists to use explained how the force decreases with experimentation to figure things out in distance. This is similar to how light science. spreads out from a source. This is ▪ He came up with the concepts behind somewhat complicated. inertia, among other things ▪ Newton also revised Kepler’s 3rd law to ▪ Kepler and Galileo were contemporaries include the force of gravity. This allows us and actually corresponded. to find the mass of an object from the orbits ▪ Galileo may have been the 1st scientist to of its satellites. For example, we can find use the newly developed telescope to the mass of Jupiter by calculating how long make astronomical observations. These it takes one of its moons to go around it. included: (possible lab) We can even use a more – The discovery of the four largest moons complicated version of this law to find the of Jupiter masses of galaxies – The discovery that planets are not just “points of light.” ▪ Newton also made other great contributions to science in the areas of – The discovery that the moon is not a optics. smooth ball, as proposed by others. – The discovery of sunspots (which ▪ He also invented Calculus, and the probably caused him blindness later) and reflecting telescope. He would not have observations of them to estimate the been surprised by space travel. He rotational period of the sun understood how we could actually leave ▪ And the discovery of the phases of Venus, the earth with his “cannon model”. which showed that Venus must orbit the sun, not the earth This was evidence supporting the heliocentric model of the LESSON 2: TELESCOPE solar system. ▪ Telescope- an optical instrument that utilizes lenses and mirrors to magnify GALILEO VS THE CHURCH distant objects, enabling us to observe ▪ Many of his observations went against the celestial bodies and phenomena that accepted geocentric model. would otherwise be invisible to the naked ▪ The heliocentric model had been banned eye. The basic components of a telescope work together in a coordinated manner to by the church Galileo was told to drop the achieve this magnification. heliocentric theory from his writing ▪ When he didn’t, he was tried by the THE ESSENTIAL COMPONENTS OF A Inquisition and was sentenced to house TELESCOPE arrest until he died. ▪ He continued to work until his death The 1.Objective Lens or Mirror church exonerated Galileo in 1992, more - is the primary optical element in a telescope, than 350 years after his death. responsible for collecting and focusing light ISAAC NEWTON from distant objects. This element is typically the largest component of a telescope, and its ▪ One of the greatest scientists who ever size determines the telescope's light-gathering lived, although not a “nice man.” Newton’s power. 3 laws of motion Orbits controlled by gravity and inertia. 2.Eyepiece -is the lens you look through to view the ▪ Law of Gravitation and Gravity activity. magnified image. It acts as a magnifying glass, further enlarging the image produced by the LIMITATIONS objective lens or mirror. Atmospheric Distortion - Earth's 3.Mount atmosphere acts as a turbulent -is the structure that supports the telescope and allows it to be pointed in different medium that distorts light passing directions. Through it. This atmospheric distortion causes twinkling of stars and blurring of 4.Tripod images, limiting the resolving power of -provides a stable base for the telescope, ground-based telescopes reducing vibrations and ensuring a clear view. Light Pollution - Artificial light from 3 MAIN TYPES OF OPTICAL TELESCOPE cities and towns, known as light pollution, interferes with astronomical 1. REFRACTING TELESCOPE - uses a observations by creating a bright CONVEX lens as the objective, which background that obscures faint celestial BENDS light rays to converge at a focal objects. point. 2. REFLECTING TELESCOPE - uses a CONCAVE mirror as the objective, ▪ Limited Wavelength Coverage - which REFLECTS light rays to Optical telescopes primarily observe in converge at a focal point. the visible light spectrum (about 400 to 700 nanometers). Their wavelength 3. CATADIOPTRIC TELESCOPE - uses a coverage is limited to this range, combination of both lenses and mirrors. meaning they can’t detect infrared, ultraviolet, or other forms of radiation. POWER ASTRONOMICAL INSTRUMENTS AND Light-Gathering Power - ability TECHNIQUES to collect and concentrate light from distant objects. A larger ▪ Photographic plate- the first image- objective gathers more light, recording device used with telescopes; it records the brightness of objects, but with resulting in brighter and more only moderate precision detailed images, especially of faint objects like distant galaxies or ▪ Photometers-Sensitive astronomical nebulae. instrument that measures the brightness of individual objects very precisely. Resolving power - ability to distinguish between two closely ▪ CCDs-Charge-Coupled Devices. An spaced objects. It is determined electronic device consisting of a large array by the diameter of the objective of light-sensitive elements used to record and the wavelength of light being very faint images. images are digitized. observed. ▪ Digitized-Converted to numerical data that Magnifying power - ability to can be read directly into a computer enlarge the image of a distant memory for later analysis. object. While it might seem like the most important power, it is actually ▪ Spectrographs-A device that separates the least significant. light by wavelengths to produce a spectrum. ▪ False-color images- A representation of launched in 2002 and has been very graphical data with added or enhanced productive in the study of violent erup color to reveal detail. tions of stars and black holes. TELESCOPE IN SPACE Fermi Gamma-ray Space Telescope Enrico Fermi Hubble Space Telescope Launched in 1999 and orbits a third of Edwin Hubble the way to the Moon the most successful telescope ever to orbit Earth Launched in 2008 and operated by an Launched in 1990 and contains a 2.4- international consortium led by the United States, is capable of mapping m (95-in.) mirror plus instruments that large areas of the sky to high sensitivity. can observe at near-infrared, visual, and near ultraviolet wavelengths. It is controlled from a research center on Earth and observes continuously. LESSON 3: THE PLANET EARTH Inner planets are expected to be high- Herschel Space Observatory density worlds because they formed from Launched in 2009, it observed from the hot inner parts of the solar nebula, behind a sunscreen. where only rock and metal particles could it could not observe from orbit around condense. Earth because Earth is such a strong Craters are found abundantly on terrestrial source of IR radiation, so the telescope planets, raising the question of their origin. was sent to a position 1.5 million km (1 The Earth's axis is tilted at an angle of million mi) from Earth in the direction about 23.5 degrees relative to the plane of away from the Sun. its orbit around the sun. This tilt is responsible for the Earth's Chandra X-ray Observatory seasons and the variation in daylight hours Chandra is named for the late Indian- throughout the year in different parts of the American Nobel Laureate world. Subrahmanyan Chandrasekhar Earth's orbital plane is the flat path that it follows as it travels around the sun. Launched in 1999 and orbits a third of The crust varies in thickness from about the way to the Moon 5-70 kilometers depending on location. It is composed primarily of solid rock and is The telescope has made important divided into two main types: oceanic and discoveries about everything from star continental crust. formation to monster black holes in The mantle makes up about 84% of the distant galaxies Earth's volume. It is composed of hot, semi- solid rock and is divided into the upper and Compton Gamma Ray Observatory lower mantle. Dr. Arthur Holly Compton One of the first gamma-ray Earth's unique features: observatories. Launched in 1991 Molten interior: Generates a It mapped the entire sky at gamma-ray magnetic field. wavelengths. The European-built INTEGRAL (International Gamma-Ray Active crust: Involves moving Astrophysics Laboratory) satellite was  continents, earthquakes, volcanoes, (about 24%). Trace amounts of other elements, such as carbon, oxygen, and and mountain building. nitrogen, make up the remaining 2%. Oxygen-rich atmosphere: A unique The Sun is classified as a yellow feature in the solar system dwarf star, which is a type of star that is relatively small and emits a yellow light. It emits light and heat due to nuclear fusion, a process where hydrogen atoms combine to form helium, releasing energy in the form of light and heat. The Sun's temperature and heat are explained by principles such as: Stefan-Boltzmann Law - Describes the power radiated by a black body in terms of its temperature. Wien's Law - States that the wavelength of the peak emission of a black body is inversely proportional to its temperature. Blackbody Radiation – the radiation emitted by a perfectly opaque object. This radiation is continuous and its characteristics depend only on the object’s temperature. THE MAIN PARTS OF THE SUN INCLUDE: Core: The central region where nuclear fusion occurs. Radiative Zone: The layer where energy is transported outward by radiation. PLANETARY DEVELOPMENT OF EARTH Convection Zone: The outer layer where energy is transported by Differentiation- merging of dense convection. material. Chromosphere: The layer above the Cratering-bombardment photosphere, visible during solar Flooding- eclipses. Slow surface evolution-tectonic plate/ Photosphere: The visible surface of natural process the Sun. Corona: The outer atmosphere of the Sun, extending millions of kilometers into space. LESSON 4: THE SUN SOLAR ACTIVITIES INCLUDE: PROPERTIES OF THE SUN Solar Winds: Streams of charged particles released from the Sun's Diameter: 1.4 million km (870,000 mi) atmosphere. Mass: about 1.989 x 10^30 kilograms. Distance (Earth): 149.6 million kilometers Sunspots: Temporary phenomena on Surface Temperature: 5,500°C the Sun's photosphere that appear as Composition: The Sun is primarily composed of hydrogen (about 74% by mass) and helium  spots darker than the surrounding -You could move the electron from one areas. energy level to another by supplying enough energy to make up the Solar Flares: Sudden eruptions of difference between the two energy energy on the Sun's surface. levels and by absorbing photon. Coronal Mass Ejections (CME): Large expulsions of plasma and magnetic Excited State: When the electron moves to a field from the Sun's corona. higher energy level, the atom is said to be in These phenomena are crucial in an "excited state." understanding how solar activity can affect Earth. De-excitation: After some time, the electron falls back to its original, lower energy level THE IMPACT OF SOLAR ACTIVITIES ON (ground state). When it does, the atom EARTH, PARTICULARLY: releases energy, often in the form of light (a Solar Flare Effects: The potential for photon). solar flares to disrupt communications and power systems. Collision - If two atoms collide, one or both Radio blackout: solar flares may have electrons knocked into higher emit intense burst of electromagnetic radiation, energy levels. particularly in the x-ray and *longest wavelength (reddest) photon - ultraviolet wavelength. shorter wavelength (higher-energy, bluer) Satellite Disruption Coronal Mass Ejection Effects: The photons possibility of CMEs causing *Jumps of electrons from one orbit to another geomagnetic storms that can affect are sometimes called quantum jumps. The satellites and power grids and Aurora: quantum jump represents a change of electron Radiation hazard: CME’s can motion, so electromagnetic radiation is either release high energy particles released or absorbed in the process. that pose a radiation hazard to astronaut in space Technological malfunctions MEASURING VELOCITIES: THE DOPPLER EFFECT Doppler effect-is an apparent change in the wavelength of radiation caused by relative LESSON 5: THE SUN II motion of a source and observer. Electron Shells -Astronomers use it to measure the speed of Columb force- the attraction that bounds the negative charge of the blobs of gas in the Sun’s atmosphere toward electrons and positive charge on the or away from Earth, as well as speeds of entire nucleus. stars and galaxies. Positive ion- is an atom with missing electrons *Sounds with long wavelengths have low Electron’s binding energy - The pitches, and sounds with short wavelengths energy needed to pull an electron away have higher pitches. from its atom. Excitation of Atoms Blueshift - a doppler shift toward -the process by which an atom absorbs shorter wavelengths caused by a energy, causing one or more of its velocity of approach. electrons to move from a lower energy level (or orbit) to a higher energy level. Redshift - a doppler shift toward longer wavelengths caused by a velocity of recession.  Maunder minimum. This coincides with the middle of a period called the “Little Radial velocity (Vr) - That component of an Ice Age,” a time of unusually cool object’s velocity directed away from or toward weather in Europe and North America the observer. from about 1500 to about 1850. -The Doppler shift is sensitive only to the part Active Region- is an area with an of the velocity directed away from you or especially strong magnetic field, up to toward you. 1,000 times stronger than the average magnetic field of the Sun. THE SUN’S CHEMICAL COMPOSITION - primary site where solar flare is produced. ATOMIC SPECTRA (KIRCHHOFF'S LAW) Law 1 : The Continuous Spectrum A solid, liquid, or dense gas excited to emit light will radiate at all wavelengths and thus produce a continuous spectrum. Law 2 : The Emission Spectrum A low-density gas excited to emit light will do so at specific wavelengths and thus produce an emission spectrum. Law 3 : The Absorption Spectrum If light comprising a continuous spectrum passes through a cool, low-density gas, the result will be an absorption spectrum. THE SUN’S MAGNETIC CYCLE Sunspots are magnetic phenomena, so the 11-year cycle of sunspots must be caused by cyclical changes in the Sun’s magnetic field. Differential rotation- the rotation of a body in which different parts of the body have different periods of rotation. Convection Zone- A region inside a star where energy is carried outward as rising hot gas and sinking cool gas. Dynamo Effect- - The process by which a rotating, convicting body of conducting matter, such as in Earth’s core or in the Sun’s convection zone, can generate a magnetic field. Babcock model- A model of the Sun’s magnetic cycle in which the differential rotation of the Sun winds up and tangles the solar magnetic field. This is thought to be responsible for the sunspot cycle. Maunder Butterfly Diagram- Historical records show that there were very few sunspots from about 1645 to 1715, a phenomenon known as the