AST201H5 Lecture Notes - Cosmological Principle, Victorian Railways E Type Carriage, Local Group

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brownelephant339

23 Oct 2012

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Essential cosmic evolution, 5th edition: measuring astronomical distances, use parallax (geometry of triangles) for the nearest stars, use cepheid variable stars for larger distances. Use the period of variation to nd the luminosity. Assumed the luminosity is the same as nearby stars of the same period. Solve for the distance: use white-dwarf supernova explosions for largest distances. Assume explosions always happen the same way producing the same lumi- nosity. Solve for the distance: existence of other galaxies, diameter of milky way = 100,000 ly (chapter 14, cepheid variables with faint apparent brightnesses other galaxies millions of ly away, types of galaxies, spiral (s) type. Bulge size ranges from small to large. Spiral arms range from loose to tight. Form is regular or barred : elliptical (e) type. Sizes range from small to huge: irregular (i) type. Actively forming stars: organize the various type using the tuning fork diagram, which is not a developmental sequence continued on page 2.

Related Questions

Astronomy Parallax Lab

SCENARIO: Your lab group is planning an expedition to measure the distance to Mars by carefully measuring its position in the sky from two locations simultaneously when it is next at “opposition” (that is, when it is exactly opposite from the sun in the sky) on October 13, 2020. For the best, and most straightforward distance determination with the parallax method, Mars should be high in the sky (as near to your zenith as possible). This can be done by observing Mars: (a) from locations whose LATITUDES are similar to the DECLINATION of Mars at the date of measurement and (b) at the time of night when Mars is highest in the sky.

1a). Determine the Sky Coordinates of Mars on the date of opposition. The relevant coordinate is the Declination (RA/DE J2000 coordinates should be used) – this is the sky coordinate analogous to Latitude on the Earth’s surface. (Note, it is ok to determine these coordinates for Mars from anywhere on Earth for this initial measurement)

Mars DECLINATION on October 13, 2020: ___________________________

Your lab team needs to send observers to two cities that:

(a) have latitudes that are similar to the declination of Mars on that date (within 20 degrees); and

(b) have nearly the same longitude (that is, are nearly due North-South from each other (hint, you will need to go close to the equator!).

1b). Choose two of the cities below and use google maps, google earth or another online resource to record their names and Latitudes.

Melbourne, Australia	Kampala, Uganda	Tokyo, Japan
Omaha, NE, USA	Mumbai, Italy	Khartoum, Soudan

1c). At what time should you measure the sky coordinates (right ascension and declination) to get the most accurate possible parallax distance?

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AST201H5 Lecture Notes - Cosmological Principle, Victorian Railways E Type Carriage, Local Group

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