Intro to Astronomy

Intro to Astronomy - Numbers... (Continued) Scientific...

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Unformatted text preview: Numbers... (Continued) Scientific Notation Scientific Notation Format Decimal Format 5.28 x 102 528 –2.9 x 103 –2 900 4.28 x 101 42.8 –4.5 x 10–1 –0.45 3.87 x 10–3 0.003 87 2.06 x 10–8 0.000 000 020 6 5.6 x 1012 2.5 x 100 9.8365 x 104 3.0 x 107 5 600 000 000 000 2.5 98 365 30 000 000 A question concerning the conversion between these could be on the test Powers of Ten Do tutorial I-2. The Concept of Infinity Infinity can be a difficult and controversial concept. Infinity is the largest of possible numbers. There is no number equal to infinity. If you propose a candidate number, simply add one to get a larger number. No matter what number you propose, infinity is larger. In fact, any number is as far from infinity as is the number one. One very large number is called the “googol.” It is equal to 10100. This is a one, with one-hundred zeros. There are only 1080 particles (of normal matter) in the visible universe, so this number is very big. The Concept of Infinity There is a number even larger than this called the “googolplex.” It is equal to 10 10 100 This is a one, followed by a googol of zeros. Because a googol is larger than the number of particles in the visible universe, a googolplex can not even be written down. Yet – a googolplex is no closer to infinity than 1. The Concept of Infinity The symbol for infinity is: ∞ (These ideas also show up in a video, later in the course.) The Concept of Infinity Q: Which interval is the largest? 1 to 1010 A) B) 1010 to 10100 10100 100 to 10 10100 to ∞ C) 10 D) 10 Systems of measurement... Scientific Measurement – The Metric System All the sciences use the metric system for measurement – astronomy is no different. During the semester measurements are stated in metric units (meters, kilograms, seconds). Metric system measurement units are related to each other by powers of ten (as opposed to the standard system where the relations are whatever number the King liked that day). During the lecture, the measurements are also given in terms of the standard system. Certain powers of ten are used so often, they are given special names. Scientific Measurement – The Metric System Power of Ten Prefix (Symbol) 10–12 = Pico (p) 10–9 = Nano (n) 10–6 = Micro (µ) 10–3 = Milli (m) 10–2 = Centi (c) 10–1 = Deci (d) 101 = Deca (da) 102 = Hecto (h) 103 = Kilo (k) 106 = Mega (M) 109 = Giga (G) Powers of Ten Do tutorial I-3. The Scale of Things (Overview) Moons orbit planets. Planets orbit stars. Stars and planets combine to form “solar systems.” Stars belong to galaxies (along with gas and dust). Galaxies form clusters (sometimes “local groups”). Clusters form superclusters. Superclusters form filaments, and walls (which surround voids). Filaments, walls and voids form the universe. The Scale of Things (Size) Small to large: Meteors/Meteorites: Small bits of rock falling through the atmosphere. Comets: Chunks of ice in orbit around the Sun. Moons: Orbit planets. Asteroids/Planetoids: Small rocks in orbit around stars. Planets: Large rocks in orbit around stars. Stars: Self-luminous spheres of gas/plasma (more details to come). The Scale of Things (Size) Small to large: (The Solar System) The Moon. Pluto. Mercury. Mars. Venus. Earth. Uranus. Neptune. Saturn. Jupiter. The Sun. Size and Distance... (Continued) The Scale of Things (Size) Small to large: (The Solar System) The Moon. Pluto. Mercury. Mars. Venus. Earth. Uranus. Neptune. Saturn. Jupiter. The Sun. The Scale of Things (Size) The Scale of Things (Size) The Scale of Things (Size) The Scale of Things (Size) Small to large: Stars: Self-luminous spheres of gas/plasma. Black Holes (downtown GR). Neutron Stars (large city). White Dwarfs (planet earth). Main-Sequence (normal) stars (the Sun). Giant/Supergiant (dying) stars (Betelgeuse). The Scale of Things (Size) The Scale of Things (Size) The Scale of Things (Size) Small to large: Star Clusters: Open Clusters (50 light-years across) Globular Clusters (100 light-years across) The Scale of Things (Size) Small to large: Nebulae: Clouds of gas and dust, light-years across. The Scale of Things (Size) Small to large: Galaxies: Large aggregates of gas, dust and stars. The Scale of Things (Size) Small to large: Local Group: A group of 35 galaxies, one of which is the Milky Way. The Scale of Things (Size) Small to large: Galaxy Cluster: 100’s of galaxies. Supercluster: Cluster of galaxy clusters. The Scale of Things (Size) Small to large: Filament/Wall: A string of superclusters. Void: A region (100 million light-years) with no galaxies. The Scale of Things (Size) Do Tutorial I-4 Ranking Task, Size & Scale, Exercise #1 The Scale of Things (Size) Do Tutorial I-5 Ranking Task, Size & Scale, Exercise #2 The Scale of Things (Size) Do Tutorial I-6 Ranking Task, Size & Scale, Exercise #3 The Scale of Things (Mass) Low to High: Meteors/Meteorites: Small bits of rock falling through the atmosphere. Asteroids/Planetoids: Small rocks in orbit around stars. Comets: Chunks of ice orbiting the Sun. Moons: Orbit planets. Planets: Large rocks in orbit around stars. Stars: Self-luminous spheres of gas/plasma (more details to come). The Scale of Things (Mass) Low to High: (The Solar System) The Moon. Pluto. Mercury. Mars. Venus. Earth. Uranus. Neptune. Saturn. Jupiter. The Sun. The Scale of Things (Mass) Low to High: (MSol = Mass of the Sun) Stars: Self-luminous spheres of gas/plasma. White Dwarfs (~MSol). Main-Sequence (normal) stars (0.1MSol – 30MSol). Neutron Stars (~2MSol). Black Holes (>MSol). Giant/Supergiant (dying) stars (>2MSol). Star Clusters: Open Clusters (100’s MSol) Globular Clusters (100,000’s MSol) The Scale of Things (Mass) Low to high: Nebulae: 1000’s MSol Galaxies: 109 MSol Local Group: 1010 MSol Galaxy Cluster: 1011 MSol Supercluster: Bigger... Filament/Wall: Even bigger... Universe: Can’t get bigger... The Scale of Things (Mass) Do Tutorial I-7 Ranking Task, Size & Scale, Exercise #4 Size and Distance... (Continued) The Scale of Things (Distance) Near to Far: Meteors/Meteorites Atmospheric The Moon: ~240,000 mi Asteroids/Planetoids: Mars-Jupiter distance Comets: To Neptune and beyond Planets: Variable, Venus closest, Neptune farthest. The Sun: 93,000,000 miles. Distances within the Solar System easily reach billions of miles. In order to decrease the size of the numbers, we change our units of measure. The Scale of Things (Distance) Distances within the Solar System easily reach billions of miles. In order to decrease the size of the numbers, we change our units of measure. The average distance from the Earth to the Sun is 150,000,000 kilometers (93,000,000 miles). We define the astronomical unit (AU) as equal to this distance. The Earth is 1 AU from the Sun. The AU is used only within planetary systems (the Solar System), not to measure between the stars – unless we are making comparisons for teaching purposes. The Scale of Things (Distance) Model of the Solar System and nearest star: Mercury: 0.4 AU. Venus: 0.7 AU. Earth: 1 AU = 1 inch. Mars: 1.5 AU. Jupiter: 5.2 AU. Saturn: 10 AU. Uranus: 20 AU. Neptune: 30 AU. Voyager spacecraft: 50 AU (~4,650,000,000 mi from Sun). The Scale of Things (Distance) Do Tutorial I-8 (LecTut document, Astronomical Distance I) The Scale of Things (Distance) The nearest star (not the Sun) to us is a star called α Centauri (alpha Centauri). This star is not visible in Grand Rapids – too far south. Its distance is 25,000,000,000,000 miles. This is about 270,000 AU. This is the nearest star!!! The Scale of Things (Distance) Q: On our model, how far away is this? A) Main Building B) Fulton Street C) Franklin Street D) 28th Street E) Kalamazoo (City of) The Scale of Things (Distance) The Scale of Things (Distance) The nearest star (not the Sun) to us is a star called α Centauri (alpha Centauri). This star is not visible in Grand Rapids – too far south. Its distance is 25,000,000,000,000 miles. This is about 270,000 AU. This is the nearest star!!! Betelgeuse (Orion) is 3,000,000,000,000,000 miles away, ~31,000,000 AU. Miles are bad, AU is not good enough. The Scale of Things (Distance) Q: On our model, how far away is this? A) 44th Street B) Kalamazoo (City of) C) Indianapolis, Indiana D) Chattanooga, Tennessee E) Miami, Florida The Scale of Things (Distance) Distance to stars: Measured in light-years. One light-year is the distance traveled by light in one year. One light-second: The distance traveled by light in one second. Speed of light: 300,000 km/sec (186,000 mi/sec). One light-second = 300,000 km (186,000 mi). Light can circle the Earth’s equator 7-1/2 times in one second. The Scale of Things (Distance) Distance to stars: Measured in light-years. One light-year is the distance traveled by light in one year. One light-minute: The distance traveled by light in one minute. mi 1 lm = 186,000 × 60 s = 11,160,000 mi s It takes light eight minutes to travel from the Sun to the Earth. The Sun is eight light-minutes away from the Earth. The Scale of Things (Distance) Distance to stars: Measured in light-years. One light-year is the distance traveled by light in one year. One light-hour: The distance traveled by light in one hour. mi s 1 lhr = 186,000 × 60 × 60 m = 669,600,000 mi s m Light-day, light-week, light-month, light-year. Possible but never seen: light-decade, light-century, ... The Scale of Things (Distance) Distance to stars: Measured in light-years. α Centauri: 4.2 light-years (ly). Betelgeuse: 520 ly. Rigel: 850 ly. Diameter of Milky Way: 100,000 ly. Distance to Andromeda galaxy: 2.2 million ly. Distance to galaxy clusters: 100’s millions of ly. Distance to edge of visible universe 13.75 billion ly. The Scale of Things (Distance) Do Tutorial I-9 (LecTut document, Astronomical Distance II) The Scale of Things (Distance) Do Tutorial I-10 (LecTut document, Astronomical Distance III) Constellations Constellations In ancient times, constellations only referred to the brightest stars that appeared to form groups, representing mythological figures. Constellations In ancient times, constellations only referred to the brightest stars that appeared to form groups, representing mythological figures. Constellations Today, constellations are well-defined regions on the sky. The “stick-figure” is irrelevant. Constellations are defined by their borders. Constellations The constellation borders were defined by the IAU in 1928 (they are the only ones allowed to name constellations, or stars.) There are 88 constellations, covering the entire sky. 48 ancient constellations (Claudius Ptolemy) 40 modern constellations (Renaissance map makers) All stars belong to a constellation, a couple belong to two (Alpheratz)! Allow us to find other objects (comets, planets, etc,...) Asterisms Asterisms are patterns of stars similar to constellations. The “Great Square” in Pegasus is an asterism. They are defined by their stick figures. Asterisms Asterisms The constellation borders are irrelevant to asterisms and asterisms themselves have no borders. The IAU does not care about asterisms. Because people can make them up for themselves, there is an unknown number of asterisms. Only bright stars are used for asterisms, some stars belong to several asterisms. Allow us to find other objects (constellations, comets, planets, etc,...) Constellations/Asterisms The stars of a constellation only appear to be close to one another Usually, this is only a projection effect. The stars of a constellation may be located at very different distances from us. Constellations Do lecture-tutorial I-11 “Constellations” LecTut.pdf document, page 10. Constellations Q: All constellations have asterisms. A) True B) False This is a really bad question! If you find a constellation involved with no known asterism, you could make-up an asterism for it. Constellations Q: All asterisms are contained within a constellation. A) True B) False Stars Stars are named with a “proper name,” many of which were created by Arabic astronomers during Europe’s “Dark Ages.” Orion Betelgeuse The names were generally related to the roll or part the star played in the constellation’s representation. For example, Betelgeuse means “arm-pit.” Rigel means “foot.” Rigel 2800 stars have proper names. Stars Stars Stars are named by a Greek letter (α, β, γ) according to their relative brightness within a given constellation + the (Latin) possessive form of the name of the constellation: Orion Betelgeuse Betelgeuse = α Orionis Rigel = β Orionis α Bayer Designation Rigel alpha β beta γ gamma δ delta ε epsilon Stars Stars Stars are named by number (1, 2, 3) according to their position (right ascension) within a given constellation + the possessive form of the name of the constellation: Orion Betelgeuse Betelgeuse = 58 Orionis Rigel = 19 Orionis Flamsteed Number Rigel Stars Stars Q: The star name, “µ Pegasi” is an example of A) a proper name for a star. B) a Bayer designation for a star. C) a Flamsteed number for a star. D) none of these. Stars Do lecture-tutorial I-12 “Star Names” LecTut.pdf document, page 11. ...
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