AST01 - Introduction to Astronomy PDF

AST01 - Introduction to Astronomy Major Historical Events in Astronomy 1054 Chinese astronomers observed the supernova that formed into Crab Nebula 1570 Tycho Brahe detailed survey of the night sky 1609 Johannes Kepler developed Laws of Planetary Motion 1687 Isaac New...

AST01 - Introduction to Astronomy Major Historical Events in Astronomy 1054 Chinese astronomers observed the supernova that formed into Crab Nebula 1570 Tycho Brahe detailed survey of the night sky 1609 Johannes Kepler developed Laws of Planetary Motion 1687 Isaac Newton developed the Universal Law of Gravitation 1781 Discovery of Uranus by William Herschel 1801 Discovery of Ceres by Giuseppe Piazzi 1846 Discovery of Neptune by Urbein Le Verrier 1930 Discovery of Pluto by Clyde Tombaugh 1957 Launch of Sputnik 1 1961 Yuri Gagarin becomes the first man in space 1965 Discovery of Cosmic Microwave Background 1975 Venera 9 becomes the first probe to land on Venus 1976 Viking 1 becomes the first probe to land on Mars 1977 Voyager 1 and 2 launch 2015 New Horizons Pluto Flyby Astronomy in the Philippines In 1865, Astronomy in the Philippines started upon the establishment of the Manila Observatory (Meteorologica De Manila) in Intramuros by Jesuit Scientists and founded by Fr. Federico Faura. In 1993, former President Fidel V. Ramos signed the Proclamation Decree No. 130 declaring the celebration of the National Astronomy Week every third week of February. In 2000, the Philippines were registered as an Associate Member of the International Astronomical Union (IAU). In 2019, through R.A. 11363 the Philippine Space Agency was established. Branches of Astronomy Cosmology - is always regarded as part of astrophysics. It is focused on the largest structure of the universe, and the universe itself by studying its origin and evolution since the Big Bang. Astrochemistry - focuses on the chemical abundance, reactions and interactions inside the stars, interstellar medium, solar system, galaxies, and of the Universe. Astrobiology - covers the life origin, evolution, and its future in the universe. It investigates the possible migration of the Human race to other worlds in the universe. Ethnoastronomy/Archaeoastronomy/Historical Astronomy - describes the unique practices, beliefs, and traditions of a certain group of people in relation to astronomy, while archaeoastronomy illustrates the recovery of cultural and analysis of astronomical material. Astronomy Education - is the branch of astronomy that deals with the transmission of astronomical learning, concepts and knowledge for formal education or community outreach. Planetology - is the study of comparative analysis of the chemical, physical, environmental, astrophysical, biological, and atmospheric inquiry of different planets in the solar system and exoplanets. Conversions in Astronomy Light Year - the distance traveled by light in one year Astronomical Unit (AU) - the average distance between the Earth and the Sun (149 million kilometers or 93 million miles) Parsec - 3.26 light years Models and Theories of the Solar System Laplace's Nebula Theory (1796): The theory states that it all began from a huge cloud of gas which was spinning slowly. This cloud collapsed under gravity. As it collapsed, it started spinning more quickly and began to flatten to conserve angular momentum. Laplace also proposed that planets were formed by the condensation of annular rings around the Sun which was one of the major drawbacks of this theory. Schmidt-Lyttleton Accretion Theory (1944): Schmidt proposed that the Sun passed through a huge cloud of gas and acquired matter to form planets. However, for his theory to be consistent, he postulated the presence of a third body in the vicinity when the Sun passed through this cloud. However, the need for the third body's presence was removed when Lyttleton gave his modification of the theory involving line accretion. In this form of accretion, mathematically described by Bondi and Hoyle. The material from the cloud gets focused gravitationally. The velocities of the material perpendicular to its orbital axis around the central object get destroyed and it is left with less than escape speed. Proto-planet Theory (1960): McCrea explained that the Solar System started with a cloud of dust and gas in a state of hypersonic turbulence. Thus, rapid internal collisions took place. This resulted in aggregation of masses at various places. He experimented with parameters like mass and radius of cloud to explain the current state of the solar system. He gave a revised theory in 1988. Capture Theory (1964): The theory is given by Woolfson and it considers an interaction between a condensed solar mass star and a protostar of lesser mass. The protostar entered the Roche limit and disintegrated to form bodies like planets. This gives a planar structure but highly elliptical orbits. The Solar Nebula Theory (1973): This theory is given by Cameron and it begins with a slowly rotating nebula very similar to the Laplacian theory. The planet formation starts with a disc of 0.01 to 0.1 solar masses. The Modern Laplacian Theory (1974): This theory is also derived from the Laplacian theory and was given by Prentice. He started with a cool gas cloud which condensed in such a way that the angular momentum of the central body was only 1 percent of the system. His contribution was mainly giving a mathematical explanation of the process of formation and the formation of planets in concentric rings. Interplanetary Bodies of the Solar System Asteroid Belt - the gap between Mars and Jupiter where hundreds of thousands of known asteroids orbit the Sun Dwarf Planets in this region: Ceres Kuiper Belt - a very distant version of the Asteroid Belt that extends from the orbit of Neptune out to a distance of well beyond 50 AU from the Sun. Dwarf Planets in this region: Pluto, Haumea, Makemake, Eris Oort Cloud - surrounds the entire solar system with a shell of frozen bits of ice and rock that stretches out to about a quarter of the way to the nearest star. Both the Kuiper Belt and the Oort Cloud are the origin of most of the comets we see. Stellar Formation Hertzsprung-Russell Diagram - Also called as HR-Diagram is one of the most important tools in the study of stellar evolution. It plots the temperature of stars against their luminosity (the theoretical HR diagram), or the color of stars (or spectral type) against their absolute magnitude (the observational HR diagram, also known as a color-magnitude diagram). We can know a star's internal structure and evolutionary stage simply by determining its position in the diagram.  Main sequence stars which 90% of the stars spend their lives in. The MS stars account for 80%-90% of the stellar population. Red giant or super red giant have high luminosities, lower surface temperature, and larger radius. Helium-burning stars. White Dwarf Stars (for mid mass stars) is the shed-off core of the red giant stars. In a spectrum, hot objects emit mostly short-wavelength radiation, while cool objects emit mostly long-wavelength radiation-hot stars are blue and cool stars are red. Nebulas, Star Clusters, Galaxies Galaxies - huge grouping of stars, planets, star clusters, nebulae, black holes, dust, dark matter, and everything else. These billions of stars are bound together by the mutual pull of gravity. Types: Lenticular Galaxies (S0 class) - with galactic disk, don't have spiral arms. Little sign of star-forming activity in their disk, dominated by old red and yellow stars. Elliptical Galaxies (E0 circular - E7 elongated) - simple ball shape. old stars and globular star clusters which imply that any star formation in these galaxies has long since ended. Spiral Galaxies (Sa - Sd (loose)) - have vast, rotating discs of stars, dust, and gas. It has a ball-shaped nucleus inside a disc with spiral arms. It is said that 25-30% of galaxies are spirals. Sa Sd (loose) Barred-Spiral Galaxies (SBa - SBd) - are spiral galaxies in which the spiral arms don't seem to emerge from the galaxy center but from the ends of a linear or football-shaped cloud of stars that straddle the center. Peculiar Galaxies - are due to galactic collisions, making a distorted shape of both galaxies. Some smaller galaxies went straight to the heart of the bigger one. Dwarf Galaxies - a few thousands light-years across, or even less. Most abundant type of galaxy in the universe. Low luminosity, and low mass. Low Surface Brightness Galaxies - They can be as large as most other galaxies, they haven't many stars, which make them not appear as bright. Although they have a full tank of gas. Galaxy Clusters - a large-scale structure in the universe consisting of hundreds to thousands of galaxies bound together by gravity. These clusters are the largest known gravitationally bound structures in the universe and can contain masses equivalent to hundreds of trillions of solar masses. - Rich galaxy clusters contain over thousand galaxies, most elliptical and more concentrated towards the center. Rich clusters often contain one or more giant elliptical galaxies at their center. Poor galaxy cluster contains fewer than a thousand (and only a few) galaxies spread through a region that can be as large as a rich cluster Milky Way Galaxy (barred spiral galaxy) Main Parts: - Bulge - Contains older, Population II stars - Disk: Contains stars, gas, and dust, with a mix of Population I (younger) and Population II (older) stars - Halo - Contains old stars, globular clusters, and a significant amount of dark matter. Star Clusters Gas and Dust - Empty spaces are not really empty but contain gas and dust particles that compose the interstellar medium (ISM). 90% by mass is composed of hydrogen, and others are traces mostly of helium. - Cold clouds or molecular hydrogen. The clouds of cold molecular and atomic hydrogen embody the raw material from which stars can be formed in the disk of the galaxy. - Hot ionized hydrogen. This is created when the ultraviolet radiation emitted abundantly by hot newly- formed stars ionizes surrounding clouds of gas. Types of Nebulae Planetary Nebula ○ are the atmosphere of old stars that started out resembling the Sun but then expelled their outer atmospheric layers. These nebulae are expanding into space and fading as they grow larger. Emission Nebula ○ a hot interstellar cloud and emitting visible light results in a glowing cloud. The young stars of type O and B produce ultraviolet radiation that can ionize the hydrogen and other atoms in these clouds Reflection Nebula ○ The cloud is not hot enough to emit visible light, dust particles reflect light from nearby stars. A human hair is 100 times wider than these tiny grains. Dark Nebula ○ a cloud of dust and cold gas, which does not emit visible light, it hides the stars it contains.