ASTR-1010 Lecture Notes - Lecture 20: Arctic Circle, Celestial Equator, Diurnal Motion

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crimsonwalrus101

22 Mar 2017

School

Vanderbilt University

Department

Astronomy

Course

ASTR-1010

Professor

Stassun Keivan

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Document Summary

What are constellations: constellations are regions of the sky, 88 constellations fill the entire sky. Locate an object by its altitude (above horizon) and direction (along horizon: know your reference points, we measure the sky in angles, 1 degree= 60 arcminutes, 1 arcminute=60 arcseconds. Celestial coordinates: declination: north or south of celestial equator, right ascension: east or west of vernal equinox. Why do stars rise and set: earth rotates from west to east, diurnal motion. Stars appear to move from east to west. Stars near the north celestial pole are circumpolar and never set: we cannot see stars near the south celestial pole, all other stars (and sun, moon, planets) rise in east and set in west. Why do(cid:374)"t we see the sa(cid:373)e co(cid:374)stellatio(cid:374)s throughout the year: depends on where you are on earth: constellations vary with latitude, depends on time of year. Sky varies with latitude but not longitude: altitude of celestial pole=latitude.

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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ASTR-1010 Lecture Notes - Lecture 20: Arctic Circle, Celestial Equator, Diurnal Motion

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