2.1 Flashcards
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
Why is a star twinkling observed? What causes it?
The effect of earth atmosphere
it is being bent by volumes of air
What is found to be within one of the north celestial pole
A faint star (polaris)
What causes seasons
Winter- sunlight strikes the northern hemisphere at a shallow angle for a short period of time
spring- the earth is tilted neither toward nor away from the sun as day and night are equal
summer-The North Pole is facing the sun, some strikes the northern hemisphere directly and the sun stays in the sky for longer
fall- The Earth spin access is tilted with respect to its orbital plane
equinox
the intersection of the ecliptic and the celestial equator.
Why do we do daylight savings
So people could have more time with the summer than winter
What are the cons of daylight savings
A causes electricity and does not save money
digital outside is better than real outside
The angle of Earth’s access is equal to what? What is the angle in degrees?
The Celestial and the Ecliptic Sun
23.5°
International date line
a crooked imaginary line on the earth’s surface roughly corresponding to ISO longitude at which when crossed from east to west the date jumps forward 1 day
15° equals to what
1 hour of right ascension
what is another name for polaris
pole star (north star)
Contrast of sidereal day in a solar day
Siberia - a day by the stars length of time that takes the vernal equinox to return to the celestial meridian
solar day- length of time that the sun takes to return to your meridian
analemma
diagram showing the position of the Sun in the sky as seen from a fixed location on Earth at the same mean solar time
contrast a constellation and an asterism
Asterism- do not make up a constellation on their own
constellation- patterns of stars visible to your eyes
Contrast a solar year and a sidereal year
Siberian- interval of time that it takes the sun to return to a given position
solar year- the interval between passings of sun through the vernal Equinox
Vernal equinox
the equinox is crossed by the sun as it moves to northern declinations
hour circles
the great circles passing through the celestial poles
sidereal time
the hour angle of the vernal equinox equal to the right ascension of objects on your meridan
tropical year
the length of time between 2 successive vernal equinoxes
Celestial sphere
an abstract sphere that has an random large radius and is concentric to Earth.
Why are summer daytimes longer than winter daytimes
Because the sun in winter is above the horizon for a shorter period of time
ecliptic
the path followed by the sun across the celestial sphere in the course of year
What does not cause seasons
Changes in the earth’s distance
where do constellations stories come from
greek mythology
Autumnal equinox
of the 2 locations in the sky where the ecliptic crosses the celestial equator that the one that the sun passes each year when moving from northern to southern declinations.
Where is 0 latitude
Equator
Constellations
one of the 88 areas into which the sky has been divided for convenience in referring to the stars or other objects there in
Meridians
The great circle on the celestial sphere that passes through the celestial poles and the observers zenith
