2.1 Flashcards
(51 cards)
Polaris
(it is the north star)
a star that appears almost above the Earth’s rotational axis.
Where is 0 longitude
The Prime Meridian
Contrast the Julian and Gregorian calendar
Julian- accurate because it had 365 days in the leap year
gregorian- years are evenly divisible by four leap years, 11 days were skipped
What other pros of daylight savings
The further the country the more use of daylight saving time
encourages people to stay out in the summer
Scintillations
The flickering of electromagnetic radiation caused by moving volumes of intermediary gas
circumpolar
stars that are close enough to the celestial pole that they never set
Right ascension
the astronomical equivalent of longitude
solstice
the point on the celestial sphere of the northernmost or southernmost declination of the sun is caused by a year, coincidentally the time when the sun reaches that point
Why don’t planets twinkle
They are close enough to Earth they can be seen through telescopes
Asterisms
A special grouping of stars, part of a constellation
How did Johann bayer assign Greek letters to start in each constellation
In alphabetical order from brightest to least
zenith
the point in the sky directly overhead on the observer (not related to celestial coordinates or to particular stars) 90% altitude
Celestial poles
The intersection of the celestial sphere with the axis of rotation of the earth
mean solar day
a solar day for the “mean sun” which moves at a constant rate during the year
midnight sun
the sun is seen around the clock from locations sufficiently for north or south at the suitable season
Precession
the slowly changing position of stars in the sky resulting from variating in the orientation of the earth’s axis
pole star
a star approximately at a celestial pole, Polaris now the pole star there is no south pole star
Declination
celestial latitude measured in degrees north or south of the celestial equator
Contrast the movement of stars when standing at the equator and standing at a pole
Equator - stars would rise perpendicularly to the horizon
pole - the north celestial code would be directly overhead and the celestial equator would be on the horizon
Celestial equator
the intersection sphere centered at the center of earth to which it appears that the stars are affixed
What are time zones? Where is each centered?
A zone on the globe that is about 15 longitude wide and extends from pole to pole and within which a uniform clock time is used
How does precision affect the cataloging of celestial positions
It has to make small corrections in any catalog of celestial positions to update them in present time
Coordinate systems
methods of assigning positions with respect to a suitable axis
Where is 90 latitude
poles
