AST101H1 Chapter Notes -Scientific Modelling, Orbital Speed, Pseudoscience

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blushbadger899

10 Oct 2012

School

UTSG

Department

Astronomy & Astrophysics

Course

AST101H1

Professor

Michael Reid

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AST101H1 Full Course Notes

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Began in central africa, where people long ago learned to predict the weather with reasonable accuracy by making careful observations of the moon. The length of our day is the time it takes the sun to make one full circuit of the sky. The length of a month comes from the moon"s cycle of phases, and our year is based on the cycle of the seasons. 7 days of the week were named after the seven naked-eye objects that appear to move among the constellations: the sun, the moon, and the five planets recognized in ancient times. Ancient societies studied the sky by: determining the time of day. Egyptians divided the daylight and night into 12 equal parts: marking the seasons. Stonehenge was both an astronomical device for keeping track of the seasons and a social and religious gathering place.

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Introduction. Telescope time is a valuablecommodity in astronomy, so astronomers plan their observationscarefully. One of the first steps is to choose what type ofobservation to make. Recall that three basic types of astronomicalobservation are imaging (taking a photograph of anobject), spectroscopy (spreading an object's light into aspectrum), and timing (measuring how an object's lightvaries with time).

Part A: Sort each of the astronomical questionsbelow into the appropriate bin based on the type of observation youwould need to perform to answer it.

Three Categories: Imagine, Spectroscopy andTiming

The Questions:

1. "What are the major surface features of Mars?"

2. "What is the temperature of Jupiter's atmosphere?"

3. "Does the star Mira vary in brightness?"

4. "How large is the Andromeda Galaxy?"

5. "What is the chemical composition of the Crab Nebula?"

6. "Is the X-ray emission fro the galactic center steady orchanging?"

7. "Is the star Vega moving toward us or away from us?"

8. "Are stars in the Orion Nebula surrounded by dusty disks ofgas?"

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Introduction: Different telescopes areoptimized for observing different wavelengths of light, so anotherconsideration in planning an observation is deciding what type oftelescope to use.

Part B: Each of the following statementsdescribes an astronomical measurement. Place each measurement intothe appropriate bin based on the type of telescope you would use tomake it.

Three Categories: Infrared Telescope, VisibleLight Telescope and X-Ray Telescope

The Statements:

1. Study a dense cloud of cold gas in space.

2. Measure the brightness of a star that is similar to ourSun.

3. Observe the hot (1-million K) gas in the Sun's corona.

4. Obtain a spectrum of sunlight reflected by Mars.

5. Determine the surface temperature of Venus.

6. Look for high-energy radiation from a supernova.

Thank you so much to whoever helps!

Tiny solid and liquid particles suspended in the atmosphere are called aerosols. Windblown dust, sea salts, volcanic ash, smoke from wildfires, and pollution from factories are all examples of aerosols. Depending upon their size, type, and location, aerosols can either cool the surface, or warm it. They can help clouds to form, or they can inhibit cloud formation. And if inhaled, some aerosols can be harmful to people's health.

These maps show average monthly aerosol amounts around the world based on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite. Satellite measurements of aerosols, called aerosol optical thickness, are based on the fact that the particles change the way the atmosphere reflects and absorbs visible and infrared light. An optical thickness of less than 0.1 (palest yellow) indicates a crystal clear sky with maximum visibility, whereas a value of 1 (reddish brown) indicates very hazy conditions.

High aerosol amounts are linked to different process in different places and times of year. High aerosol amounts occur over South America from July through September. This pattern is due to land clearing and agricultural fires that are widespread across the Amazon Basin and Cerrado regions during the dry season. Aerosols have a similar seasonal pattern in Central America (March-May), central and southern Africa (June-September, and Southeast Asia (January-April).

In other cases, however, aerosol concentrations are not related to fires. For example, from May through August each year, aerosol amounts rise dramatically around the Arabian Peninsula and nearby oceans due to dust storms. Elevated aerosol amounts nestle at the foothills of the Himalaya Mountains in northern India in some months, and linger over eastern China for much of the year. These elevated aerosol amounts are due to human-produced air pollution.

What is the most likely source of the high concentration of particulates that appear off the coast of northwestern Africa?

What is the most likely source of the high concentrations of particulates over central Africa and central South America?

What is the most likely source of the high concentrations of particulates over eastern China?

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AST101H1 Chapter Notes -Scientific Modelling, Orbital Speed, Pseudoscience

AST101H1 Full Course Notes

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