Survey of the Universe Tom Burbine

Readings Should start reading Units 1-4

Stellarium Everybody should download the program Stellarium Need to change your location

Office Hours M-W am in Kendade 221

Help Sessions 7-10 pm on Sundays and Tuesdays First Help Session will be Feb. 3 in Kendade ( on room number later)

HW #1 HW #1 is due Feb. 6

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

Stellar evolution Stars are born Live And then die

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 billion stars

Galaxies Taken over 11 days Over 10,000 objects apparent (majority are galaxies)

There are estimated to be more than 176 billion galaxies in the observable universe

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

Big Bang Explosion that started the Universe

Why do we use the metric system in science?

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 km altitude above Mars during orbit insertion, instead entering the Martian atmosphere at about 57 km. The spacecraft was destroyed

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 How is the meter defined?

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 How are the gram and kilogram defined?

Gram and Kilogram How are the gram and kilogram defined?

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 10 8 m/s

Scientific Notation = = = = = = 10 -7

How do you write numbers? 31,700,000 = 3.17 x ,770,000 = 2.77 x = 5.6 x = 7.8 x 10 -6

How do you do multiply? 10 6 x 10 8 = 10 (6+8) = x 10 3 = 10 (-5+3) = (3 x 10 4 ) x (4 x 10 5 ) = 12 x 10 (4+5) = 12 x 10 9 = 1.2 x 10 10

How do you divide? 10 8 /10 6 = 10 (8-6) = /10 -4 = 10 (-6-(-4)) = (3 x 10 8 )/(4 x 10 3 ) = ¾ x 10 (8-3) = 0.75 x 10 5 = 7.5 x 10 4

Always use units for your answers

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 10 9 ) x (100 x 10 9 ) = x = 1 x = 10,000,000,000,000,000,000,000 This is about the same number of grains of sand in every beach in the world

Questions: How many of these stars have planets? How many of these planets have life?

Any Questions?