Today in Space News: Pluto and Charon tattle on missing Kuiper Belt objects

Transcription

1 Today in Space News: Pluto and Charon tattle on missing Kuiper Belt objects

2 Study Points Define blackbody radiation. Draw two graphs of intensity vs wavelength for the low temperature object (reddish) and the high temperature object (bluish). What happens to the graph if the temperature of the body increases? Define and differentiate between the following: atom, element, molecule Identify the three basic particles in an atom. Know whether their charge is positive or negative or neutral. Know their approximate relative masses (not the mass itself, just how they compare). Know where each is located in the atom. Describe or sketch a simple model of the atom (the Bohr model) including permitted orbits. Given a model of the atom, show which jumps correspond to emission spectra and which to absorption spectra. Given a model of the atom showing several energy levels, identify which photon comes from which electron transition. What information can astronomers obtain from the spectrum of a star, galaxy or gas cloud? What did Annie Jump Cannon contribute to the study of spectra? Cecilia Payne? State the two chief components of stars. What percent is each? Discuss how astronomers can tell what elements are in a gas cloud or in a star.

3 Blackbody Radiation Atoms and Light 2 3 1

4 Blackbody Radiation Spectra Definition: Radiation emitted by a heated object* When not heated, the object is black When heated, the object varies in color depending on the temperature Continuous spectrum A blackbody absorbs and emits radiation Cooler object less radiation Hotter object more radiation

5 Examples: Blackbody Radiation Spectra Incandescent light bulb Filament changes color as it is heated Hot lava Sun and other stars Heated metal

6 Blackbody Radiation Spectra Examples Cooler Objects Emit less radiation Appear reddish Hotter Objects Emit more radiation Appear yellowish

7 Light Bulb Filament & Demonstration Solve: Are there vibrations of the atoms in the filament? 1. Are there many atoms or a few atoms in the metal filament? 2. True or False: Each atom vibrates at some frequency. 3. True or False: All atoms vibrate at the same frequency. 4. Why does an object change color when heated? Explain. 5. Are there vibrations of the atoms in the filament?

8 Light Bulb Filament & Demonstration Solve: Are there vibrations of the atoms in the filament? 1. Are there many atoms or a few atoms in the metal filament? MANY ATOMS

9 Light Bulb Filament Solve: Are there vibrations of the atoms in the filament? 1. MANY ATOMS in the metal filament. 2. True or False: Each atom vibrates at some frequency. TRUE

10 Light Bulb Filament Solve: Are there vibrations of the atoms in the filament? 1. MANY ATOMS in the metal filament. 2. Each atom VIBRATES at some frequency. 3. True or False: All atoms vibrate at the same frequency. FALSE Not all vibrate at the same frequency Many different frequencies

11 Light Bulb Filament Solve: Are there vibrations of the atoms in the filament? 1. MANY ATOMS in the metal filament. 2. Each atom VIBRATES at some frequency. 3. Atoms vibrate at DIFFERENT frequencies. 4. Why does an object change color when heated? Explain. Different frequencies correspond to different wavelengths and display different colors. Blue light = 400 nm Red light = 700 nm

12 Light Bulb Filament Solve: Are there vibrations of the atoms in the filament? 1. MANY ATOMS in the metal filament. 2. Each atom VIBRATES at some frequency. 3. Atoms vibrate at DIFFERENT frequencies. 4. Why does an object change color when heated? Explain. 5. Are there vibrations of the atoms in the filament? YES

13 Blackbody Radiation Spectra Examples: body-spectrum Side Note: Intensity = Energy/surface area Temperature α Energy

14 Which star is hottest? How do you know?

15 Which star is hottest? How do you know? Hotter object (higher temperature) has: More overall radiation (intensity)* Higher peak* Be able to draw Intensity vs. Wavelength graphs*

16 Spectrum of the Sun What do you know from this spectrum? Absorption hot dense object with a gas cloud Mix of gases (but which ones?)

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18 Spectra Spectra Other stars show similar but not identical line patterns. So why are there lines in the spectra at all? What do those lines mean?

19 Spectra of stars (differences)

20 Intensity difference

21 Line differences are element differences

22 Annie Jump Cannon* Harvard around 1900 Sorted hundreds of thousands of stars by their patterns of spectra lines. Discovered patterns among star spectra Spectra lines are different for different elements* Hotter Cooler UV Longer λ λs?, visible?, Temperatures?

23 Annie Jump SpectraCannon Hotter Cooler O B A F G K M { { { { { { Blue Red Lines used to categorize wavelength & temperature Still used today and extended past M for darker red and brown stars.

24 Spectra Spectra So why are there lines in the spectra at all? And What do those lines mean?

25 Definitions Spectra Element* More than 100 substances that cannot be broken down any simpler Atom* Basic unit of a chemical element Has protons, neutrons, & electrons Molecule* Group of atoms

26 Atoms Spectra Protons positive charge ( + ); larger mass* Neutrons neutral, no charge; larger mass* Electrons negative charge ( - ); smaller mass* Nucleus protons and neutrons* Surrounded by orbiting electrons*

27 Quantum Mechanics Study of atoms and subatomic particles Bohr Model (be able to draw this*) Ground state - Lowest energy level 1. Electrons have certain orbits and not others 2. Orbits are closer together as you get further from the nucleus

28 Quantum Mechanics Absorb = take in (ex. Increase energy) Emit = give off (ex. Decrease energy) Emission Spectrum: When an electron jumps down, it emits all the energy at once in a bundle called a photon (the energy is quantized as a packet). Electron emits energy.* Absorption Spectrum: If an electron absorbs a photon of just the right energy, it jumps up. Electron absorbs energy.*

29 Of the electron jumps shown, which number of jump(s) EMITS (gives off) a photon?

30 Of the electron jumps shown, which number of jump(s) EMITS (gives off) a photon?* 2 and 3 Decrease in energy

31 Of the electron jumps shown, which number of jump ABSORBS (takes in) a photon?

32 Of the electron jumps shown, which number of jump ABSORBS (takes in) a photon?* 1 Increase in energy

33 For the atom shown, a blue and a green photon are emitted and a red photon is absorbed. Which jump corresponds to emitting a blue photon? Which jump corresponds to emitting a green photon? Which jump corresponds to absorbing a red photon?

34 For the atom shown, a blue and a green photon are emitted and a red photon is absorbed.* Which jump corresponds to emitting a blue photon? 2 Which jump corresponds to emitting a green photon? 3 Which jump corresponds to absorbing a red photon? 1

35 Cecilia Payne-Gaposchkin* Surveyed star spectra Discovered stars are about 90% hydrogen and 10% helium*

36 Spectra Lines Tell us what elements are in the spectra (Annie Jump Cannon)* Tells us how much of each element is in the spectra (Cecelia Payne-Gaposchkin)*

37 Cosmos: A Spactime Odyssey (2014) with Neil degrasse Tyson Episode 8: Sisters of the Sun

38 Homework and Announcements Continue working on STUDY POINTS Pay attention to quizzes! No lab today, but lab Tues/Thurs next week. Check calendar if unsure! Sunset Part 1 Due Today! Submit by D2L, , or hand in to me. Work on Moon Phases Observation due March 7 Work on Planetarium, Star Gazing, Telescope, Moon Craters and News Report due May 14 Planetarium Field Trip: Being rescheduled. Keep an eye out for s.