Astronomy 100 Tuesday, Thursday 2:30 - 3:45 pm Tom Burbine

Help Desk There is an Astronomy Help Desk in HAS 205. It will be open from Monday through Thursday from 7-9 pm.

OWL HW Due Tuesday at March 8 th by 11:59 pm

By Thursday I will put on OWL everybody’s HW and PRS scores so far

Test Thursday March 10 th 40 questions Will cover Chapters 4, 5, 6, and 7 Will not cover Supplemental chapters 2 and 3 If there is a problem with taking the test on March 10th, I need to know today I will give you all constants you need to know But you need to memorize formulas Bring pencil

Test Rooms People who last names begin with A and B will be in Hasbrouck 137 Everybody else will be in Hasbrouck 20

Constants (given on top of test) c = 3 x 10 8 m/s G = 6.67 x m 3 /(kg s 2 ) h = x joule second g = 9.8 m/s 2

Formulas E = mc 2 KE = ½ mv 2 c = frequency * wavelength E = h*frequency F = mass * acceleration Angular momentum = m * v * r F = G M 1 M 2 distance 2

You should be acquainted with Escape velocity = square root (2GM planet /R planet ) Stefan-Boltzman Law Emitted power per square meter = σ T 4 σ = 5.7 x Watt/(m 2 Kelvin 4 ) Wien’s Law Wavelength (maximum intensity) = 2,900,000 nm T (Kelvin)

Figure 6.13

Figure 6.6

Things you definitely should know Doppler Shift Calculating energy Tides Newton’s 3 Laws Temperature conversion from Kelvin to Celsius Atomic Mass, Atomic Number What is in the nucleus Energy Levels and the transitions

Things you be acquainted with Periodic Table How energy, frequency, and wavelength are related gravitational acceleration General information on telescopes and observing

Percentages 100% = % = 0.1 1% = % = 0.001

Hints for studying Go over my notes Go over all figures I showed in class Make sure you can use the formulas

Hints for taking Test Read the whole question carefully Read all the answers Check your math Do calculations by hand and by using calculator

Review Session I will have a review session on Wednesday March 9 from 7-9 PM in Goessmann Laboratory room 20.

Is everybody okay?

Telescopes Why do we use telescopes?

Initially Everybody observed with their eyes

Figure 7.1

Figure 7.2a Parallel lightLens

Figure 7.2b

Why are Telescopes better than your eyes? They can observe light in different wavelength regions (eyes can only see visible light) They can collect more light than eyes They can be built to compensate for the distorting effects of the atmosphere

Figure 7.6 Refracting telescope

Figure 7.7 Reflecting Telescope

Reflecting Telescopes Figure 7.8

Why are reflecting telescopes used more in astronomy? Since light passes through the lens of a refracting telescope, You need to make the lens from clear, high- quality glass with precisely shaped surfaces

It is Its easier to make a high-quality mirror than a lens

Also, Large lenses are extremely heavy

Size of a telescope Diameter of its primary mirror or lens Light collecting area is proportional to the diameter squared since Collecting area =  r 2 E.g., 8-meter telescope

To measure light In the past, they used photographic plates Now they use CCDs (charge-coupled devices) CCD are electronic detectors CCDs are chips of silicons

Figure 7.5

CCDs CCDs can collect 90% of photons that strike them Photographic plates can only collect 10% of the photons CCDs are split into squares called pixels Data is in electronic form

Atmosphere Atmosphere can absorb light Atmosphere can scatter light Atmosphere can distort light (twinkling)

Twinkling Twinkling of stars is caused by moving air currents in the atmosphere. The beam of light from a star passes through many regions of moving air while on its way to an observer’s eye or telescope. Each atmospheric region distorts the light slightly for a fraction of a second.

Advantages of space-based telescopes It can be open 24 hours, 7 days of week Do not have to worry about distorting effects of atmosphere There is no extra background of light due to scattering of light in the Earth’s atmosphere Observe in more wavelength regions

Figure 7.20

It does not help That you are closer to the stars

Hubble Telescope Can observe in visible, infrared, and ultraviolet wavelength regions

Hubble Figure 7.19b Telescope is the size of a school bus

Jupiter

Video

Attendance PRS

Questions?