survey of the universe tom burbine tburbine@amherst.edu
Post on 26-Dec-2015
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Stellarium
• Everybody should download the program Stellarium
• http://www.stellarium.org/
• Need to change your location
Help Sessions
• 7-10 pm on Sundays and Tuesdays
• First Help Session will be Feb. 3 in Kendade (email on room number later)
Stars
• Stars are composed primarily of Hydrogen and Helium
• Generate energy through nuclear fusion
Sun
• Our star
• Typical star since the msses of stars range from 0.1 to 100 solar masses
• 1 solar mass is the mass of the Sun
http://www.aerospaceguide.net/solar_system/sun.html
Galaxies
• Galaxies are massive gravitationally bound systems of stars and stellar remnants, gas, dust, planets, and dark matter
• Dark matter is matter that you can’t see but whose gravity affects visible matter and background radiation
Milky Way Galaxy
• Our Galaxy
• 100-400 billion stars
http://www.astro.keele.ac.uk/workx/milkyway/page.html
Light-year
• Distance that light travels in a year
• Light travels at a speed of 300,000,000 m/s in a vacuum
• 1 light year = 10,000,000,000,000,000 meters
Local Group
• Gravitationally bound group of galaxies that the Milky Way is a member of
• Contains more than 30 galaxies
http://hendrix2.uoregon.edu/~imamura/123/lecture-3/lecture-3.html
• A system based on multiples of 10 is much more intuitive for humans
• We are born with 10 fingers and toes
• The math system that we use is based on 10
Metric System
• Any system of measurement needs three fundamental units– Length - meter– Mass - kilogram– Time - second
• 1 kilometer = 1,000 meters
• 1 meter = 100 centimeters
• 1 centimeter = 10 millimeters
• 1 kilogram = 1,000 grams
Things you need to know because we will use the metric system
• one kilometer is 5/8 of a mile
• one meter is 3.28 feet
• one centimeter is 0.39 inches
• 1 kg (mass) is equivalent to 2.2 pounds (force) on Earth
• We will use the metric system in this class
• Does anybody remember the Mars Climate Orbiter?
Mars Climate Orbiter• Software calculated forces for the
thrusters in English units (pounds). • People controlling the spacecraft thought
the calculated forces were in Newtons (metric). (One English pound of force equals 4.45 Newtons.)
• Changes made to the spacecraft's trajectory were actually 4.45 times greater than what the JPL navigation team believed.
• The spacecraft missed its intended 140 - 150 km altitude above Mars during orbit insertion, instead entering the Martian atmosphere at about 57 km.
• The spacecraft was destroyedhttp://en.wikipedia.org/wiki/Image:Mars_Climate_Orbiter_2.jpg
• 1 kilometer = 1,000 meters
• 1 meter = 100 centimeters
• 1 centimeter = 10 millimeters
• 1 kilogram = 1,000 grams
• one kilometer is 5/8 of a mile
• one meter is 3.28 feet
• 1 kg (mass) is equivalent to 2.2 pounds (force) on Earth
Meter
• Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole
• International Prototype Meter was defined as the distance between two lines on a standard bar composed of an alloy of ninety percent platinum and ten percent iridium, measured at the melting point of ice.
Meter
• Now defined as equal to the distance travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second.
Gram and Kilogram• A gram was first decreed to be equal to “the absolute
weight of a volume of water equal to the cube of the hundredth part of the meter, at the temperature of melting ice.”
• Now, the International Prototype Kilogram is used as the standard.
• It is made of a platinum alloy known as “Pt‑10Ir”, which is 90% platinum and 10% iridium
International Prototype Kilogram
• Photo of Danish national
kilogram prototype
Other Units used in Astronomy
• Solar mass – Mass of Sun
• Jupiter mass – Mass of Jupiter
• Light year – Distance light travels in a year
• Astronomical Unit – Average distance between the Sun and the Earth
• Speed of light (c) - 3 x 108 m/s
Scientific Notation
• 10000 = 104
• 100000000 = 108
• 10000000000 = 1010
• 100000000000000000000 = 1020
• 0.001 = 10-3
• 0.0000001 = 10-7
How do you write numbers?
• 31,700,000 = 3.17 x 107
• 2,770,000 = 2.77 x 106
• 0.00056 = 5.6 x 10-4
• 0.0000078 = 7.8 x 10-6
How do you do multiply?
• 106 x 108 = 10(6+8) = 1014
• 10-5 x 103 = 10(-5+3) = 10-2
• (3 x 104 ) x (4 x 105) = 12 x 10(4+5) = 12 x 109 = 1.2 x 1010
How do you divide?
• 108/106 = 10(8-6) = 102
• 10-6/10-4 = 10(-6-(-4)) = 10-2
• (3 x 108)/(4 x 103) = ¾ x 10(8-3) = 0.75 x 105 = 7.5 x 104
Stars in the Universe
• Say there are 100 billion galaxies
• Each galaxy has 100 billion stars
• So how many stars in the universe
Answer
• Number of stars in universe
• = (100 x 109) x (100 x 109) = 10000 x 1018
= 1 x 1022 = 10,000,000,000,000,000,000,000
• This is about the same number of grains of sand in every beach in the world
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