Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine

Course Course Website: – Textbook: –Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny. You also will need a calculator.

Office Hours Mine Tuesday, Thursday - 1:15-2:15pm Lederle Graduate Research Tower C 632 Neil Tuesday, Thursday - 11 am-noon Lederle Graduate Research Tower B 619-O

Homework We will use Spark owebcthttps://spark.oit.umass.edu/webct/logonDisplay.d owebct Homework will be due approximately twice a week

Astronomy Information Astronomy Help Desk Mon-Thurs 7-9pm Hasbrouck 205 The Observatory should be open on clear Thursdays Students should check the observatory website at: for updated information There's a map to the observatory on the website.

Final Monday 12/14 4:00 pm Hasbrouck 20

HW #5 There is a HW #5 replace which will replace your HW #5 score if you get a higher grade F = G M 1 M 2 r 2 G = 6.67 x m 3 /(kg  s 2 )

HW #6 Due today

HW #7 Due next Thursday

Atoms make up molecules H 2 O - water CO 2 – carbon dioxide CH 4 - methane

Spectroscopy Spectroscopy is the study of the interaction between radiation and matter as a function of wavelength (λ). You can use spectroscopy to determine what is in a body (planet, star, etc.) or atmosphere

How did scientists recently determine that there was water on the Moon?

Water on the Moon White line - NASA' Cassini spacecraft Blue line - NASA's Moon Mineralogy Mapper instrument on the Indian Chandrayaan-1 spacecraft Grey - H 2 O and OH absorptions

Definitions Reflectance – How much light an object reflects Absorption – Light is absorbed and not reflected

Light cause water molecules to vibrate htmlhttp:// html

How much water? If you had a cubic meter of lunar soil, you could squeeze it and get out a liter of water Water has to be near the surface

How do you use light to determine what is in an astronomical body like a star?

bcMfLKeghttp:// bcMfLKeg

What happens when electrons absorb energy?

Energy levels where an electron can reside To go to a higher energy level, an electron needs to gain energy To go to a lower energy level, an electron needs to lose energy

eV 1 eV = 1.6 x Joules

Rules An electron can not jump to a higher energy level unless it gains energy from somewhere else –Absorbs a photon –Gains kinetic energy from an impacting particle To go to a lower energy level, the electron must lose energy –Emits a photon Electron jumps can occur only with the particular amounts of energy representing differences between possible energy levels

Heated hydrogen gas Emission line spectrum White light through cool hydrogen gas Absorption line spectrum

Types of spectra Emission – radiation is emitted at characteristic wavelengths –Material is “hot” so electrons keep on bumping into each other and transferring kinetic energy to each other so they jump between particular energy levels Absorption – radiation is absorbed at characteristic wavelengths –Radiation passes through the material

So why is this important Different elements have different number of electrons Different elements have different energy levels for their electrons

So Different elements can absorb light at specific energies Different elements can emit light at specific energies So if you can measure the wavelength of the light from an astronomical body, you can determine whats in it

Emission line spectra

How can you determine velocities of objects? Doppler Shift – The wavelength of light changes as the source moves towards or away from you Since you know the wavelength position of emission or absorption features If the positions of the features move in wavelength position, you know the source is moving

So Source moving towards you, wavelength decreases –blueshift Source moving away from you, wavelength increases –redshift

nanometer 1 nanometer = 1 x meters

Formulas for light v rad /c = λ shift – λ rest λ rest Rest wavelength of a line of hydrogen is at nm You observe this line at nm for a star What is the velocity of this star? v rad /c = ( )/ nm v rad /c = x v rad = x *3 x 10 8 m/s = -13,700 m/s = km/s It is blue-shifted so the motion is toward us

Blackbody A black body is an object that absorbs all electromagnetic radiation that falls onto it. Perfect emitter of radiation Radiates energy at every wavelength

Stefan-Boltzman Law - energy radiated per unit surface area of a black body in unit time is directly proportional to the fourth power of the black body’s temperature Wien’s Law - blackbody curve at any temperature has essentially the same shape as the curve at any other temperature, except that each wavelength is displaced, or moved over, on the graph

Stars and planets act can be modeled as blackbodies

Any Questions?