Astronomy 5L Due 2nd meeting Name : ______This page & the coordinate systems worksheet are due at the beginning of the 2nd meeting!

Define the following important astronomy words: Look up the definition, explain in your own words! Constellation: ______

______

______

Apparent magnitude: ______

______

______

The brightness of an apparent magnitude 1 star is ______times brighter than an m= 5 star.

Show calculations.

Multiple stars:

Visual binary (double): ______spectroscopic binary (double): ______

Optical binary (double): ______

Galaxies:

Elliptical galaxy: ______

Spiral galaxy: ______

Irregular galaxy: ______

The Milky Way is a(n) ______galaxy.

Star clusters:

Open star cluster: ______

Globular star cluster: ______

Nebulae:

Absorption (dark) nebula: ______

Reflection nebula: ______

Emission nebula: ______

Planetary nebula: ______

Supernova remnant: ______

1 A

B

C

D

E F G H

2 Name : ______Agenda for today: Go over syllabus Homework due next meeting: definitions & coordinate systems Measurement lab Let’s start with angular measurement! Be sure to write your name & answer all short answer questions in complete sentences.

Measurements and Numbers in Astronomy Astronomy is a branch of science. You will be exposed some numbers expressed in SI units, large and small numbers, and some numerical operations such as addition / subtraction, multiplication / division, and ratio comparison. Lets watch part of a IMAX movie called Cosmic Voyage. http://www.youtube.com/watch?v=1BX-lfK5JLI or http://www.videosurf.com/video/cosmic-voyage-excerpt-61169985?t=18

Scientific notation or powers of 10 notation Astronomy is a subject of extremes (very large numbers and very small numbers) Examples include how many stars in the universe, how many galaxies, the distance to far away stars, length of time, density of giant molecular gas clouds, wavelength measurements, etc. For these very large and very small numbers, it is convenient to use “powers of 10” (or “scientific”) notation. Powers of ten notation expresses the number by using multiples of 10 with exponent numbers. Often a single digit is followed by the decimal point and any other digits, then the exponent. For large numbers: For small numbers: 1 no zero = 10 0 10 1 zero = 10 1 0.1 = 1/10 Divided by 10 =10 -1 100 2 zero = 10 2 0.01 = 1/100 Divided by 100 =10 -2 1000 3 zero = 10 3 0.001 = 1/1000 Divided by 1000 =10 -3

Exercise: Example: 200 = 2 x 100 = 2 x 10 2 1500 = 1.5 x 1000 = 1.5 x 10 3

40,000 = 9,000,000 =

12,700 = 380,000 = example: 0.017 = 1.7 x 10 -2 0.003 =

0.0000005 = 0.00205 =

3 Distance or length measurements In astronomy, we use meters (or variations of that: km, cm, mm, nm etc), astronomical units and light years. To measure the distance to objects that are nearby or to measure size of an object we generally use km. For distance within the solar system, we use astronomical units. For far away objects, light years are used. Complete the chart below: For some part, you must use a ruler to make measurements.

Convert to: If the # is large or small, Object Unit be sure to use sci notation

Your astronomy book cm m

2 meter stick m cm

Pen cm m

Your height cm m

Wave length of green light 550nm m

Radius of the Earth 6,400,000 m km

The distance light travels in one 300,000km m second.

1km = 1000m, 1m = 100cm, 1m = 1,000,000,000nm

4 For the following calculations, please show your work and draw a box around your final answer. Please check if you have the correct unit for the final answer.

Astronomical unit: average distance between ______and ______. 1AU = 1.5x108km

Mercury’s average distance form the sun is 57,900,000km. Show this # in AU: ______

Jupiter’s average distance from the sun is 5.2 AU. Show this # in km: ______

Light Year: distance that light travels in vacuum in one year: 1 ly = 9.5x1012km = 63,000 AU Nearest star, Proxima Centauri is 4.2 lys away. Show this # in km:

The brightest star in the night sky, Sirius, is 8.6 ly away. Show this # in km:

Temperature In astronomy we use the Kelvin as unit of temperature (1K is the same incremental value as 1°C). The Kelvin scale is named after British physicist Lord Kelvin. In the Kelvin scale, water boils at 373K and freezes at 273K. To convert:

Fahrenheit and Kelvin: TK = (5/9)*(TF – 32) + 273 or TF = (9/5) * (TK -273)+32 o Example: let’s say it is 75 F in this room. TK = (5/9)*(75– 32) + 273 = 297K

Water boiling temperature 373K oF

Surface temperature of Titan K -290 oF (Saturn)

Surface temperature of Mercury at K 750 oF hottest

Surface temperature of the Sun 5800K oF

Show sample calculation:

5 Angular Measurements: The Ancients invented angles and a system of angular measurement that can be used to pinpoint a direction as well as the apparent size of the object far away. o • Circle is broken up into 360 equal segments, called degrees (circle = 360 ) o • One degree is further divided into 60 segments, called arc minutes (1’ = 1/60 ) o • One arc minute is divided into 60 segments, called arc seconds (1” = 1/60‘ = 1/3600 )

Circle demo In astronomy we often measure the angular size of celestial object before we truly find out the actual size of the object. Following exercise is to help you gain better feel for angular measurements!

At arm’s length, which circle do you think is closest to the diameter of the Sun? ______

Go outside and stand on a blue “X.” Measure the angular sizes of various objects from where you stand, using your “hand tools.”

Station Object Estimated angular size (o) Height from the ground to the top of the 1 Building 60 railing: Height from the ground to the top of 1 Building 7: Height from the ground to the top of the 2 Building 60 railing:

Height from the ground to the top of 2 Building 7:

Height from the ground to the top of the 3 Building 60 railing:

Height from the ground to the top of 3 Building 7: Width of one pane of window on 1st floor of 3 building 7: Height of the number “60” of the northeast 3 corner:

What do you conclude from comparing your observations from stations 1 and 2?

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