Unit 1: Discovering the Night Sky Flashcards
What did ancient greeks believe about the earth?
- that the earth was flat, floating on ocean, surrounded by animals and life
What did the bible say about the earth?
- that the earth in flat, ocean all around (ocean of heaven) and Heaven of heaven’s
- earth and water are separated by solid mass
- underworld (tartar)
How are planets named?
- all planets are named after Greek Gods, except for earth
What is the Milky Way?
- where we live, and is 9 hundred and 25 quadrillion km’s
- 9.25x10^17 km
- the middle of the milky way is more interesting but more dangerous
How many stars are there in the universe?
- 100 Billion- 200 Billion stars
How many galaxies are there in the universe?
- 100-200 Billions galaxies
- all galaxies have a different number of stars
Approximately how many stars can we see in the night sky with the naked eye?
- 6000 stars can be seen by the naked eye
- 3000 In north and 3000 in south
What did the Greeks and Romans consider constellations to be? How did they used to label stars?
- patterns of heroes and monsters
- they used to label stars along with the alphabet from the most bright to the least bright
How many official constellation regions of space have modern astronomers divided the sky into?
- 88 official constellations
- feeding off past patterns from ancient greeks
What is Polaris?
- the north star
- at the end of Ursa Minor (little dipper)
What is Sirius?
- the brightest star other than the sun, moon and venus
What are the apparent cyclic motions of the sun and stars in our sky do to?
3 things
- the movement of the earth
1. Rotation: the spin of the earth on it’s axis, it takes one day for the earth to complete 1 rotation
2. Revolution: the movement of the earth in orbit around the sun , its takes one year for the earth to complete one revolution
3. Precession: the slow conical motion of the earths axis of rotation , this takes about 26000 years for the earth to complete 1 cycle of precession
Which way do the stars move when viewing them from the north pole?
- horizontally
Which way do the stars move when viewing them from the equator?
- vertically
Which way do the stars move when viewing them from middle latitudes?
- diagonally
What is unique about the stars near the poles on the celestrial sphere
- the stars near the poles of the celestrial sphere move in trails that circle that pole (polaris)
- these stars don’t set below the horizon
What does the view of the star’s movement depend on?
- our latitude
Explain Foucault’s experiment in 1851 with the Pendulum
- the pendulum was introduced in 1851 and demonstrates the earth’s rotation
- hung pendulum from a ceiling and created a pattern that effectively proved the world is spinning on an axis and it moves as a unit
Explain the movement of a Pendulum at the equator
- it will move faster, tracing smaller circles each day at the extreme N and S latitudes
- during shift pendulum would not be distorted at all
Explain the movement of a Pendulum at the north pole
What is the due to
- small changes in latitude have big implications
- this shift of the pendulum would be easily distinguished
What is Latitude vs longitude?
- latitude: distance from the equator in degrees
- longitude: equator, north or south
What is another name for latitude and longitude
- latitude is also called parallels
- longitude is also called meridians
What is altitude?
- above compared to sea level
Why where time zones created?
- for convenience as travel times shrunk
What is astronomical noon?
- when the sun hits the highest point in the sky
- this is different in different time zones
- at noon on a shadow clock, the shadow is the shortest
How many different time zones are there?
- 24
What is the International Date line?
What happens when you cross it from west to east?
What happens when you cross it from east to west?
- an imaginary line on the earth that separates two consecutive calendar days
- cross it from west to east: back one calendar day
- cross it from east to west: gain one calendar day
- the date in the eastern hemisphere to the left of the line is always one day ahead of the date in the western hemisphere
Who invented time zones?
- Sir Standford Fleming
What is the celestrial sphere?
- an imaginary sphere surrounding the earth on which all objects in the sky can be located
Why dont we use altitude to measure placement in space?
- because it is very hard to tell the depth in space.
What is Declination ?
- latitude of celestrial sphere
What is Ascension?
- longitude of celestrial sphere
- prime meridian
How does the Celestrial sphere appear to rotate?
- on 2 axis (like earth)
- the norther and southern celestrial poles
- located directly above the earths poles
What does the celestrial equator do?
- it divides the celestrial sphere into northern and southern hemispheres
How do we define the position of an object on the celestrial sphere?
- using two coordinates
- right ascension and the declination
Do Celestrial coordinates move?
- celestrial coordinates of the sun are always moving from our perspective but it actually stays in the same place and we move (earth)
- earth revolves around the sun which shifts our view of the stars
How many constellations are within the ecliptic plane
- 12 constellations
- sun visits once a month
Describe the sun in the summer?
- the sun is high in the sky during mid-day
- the shaft of sunlight is more concentrated onto a small area which heats the ground effectively and makes the days warm
- there are longer days
Describe the sun in the winter?
- the sun is low in the sky during mid-day
- the shaft of sunlight is more spread out so heating the ground less
- shorter days
What are seasons caused by?
- the earths axis is tilted and as the earth revolves around the sun, different parts of the earth receive more direct sunlight (summer) while others receive sunlight that is more spread out (winter)
- the seasons we experience are linked to the motion of the sun along the celestrial sphere
Which hemisphere does the sun always hit more directly?
- the northern hemisphere
What is the degree of the earths axis
- 23 1/2 degrees
What is the furthest sun path point called ?
What day is it on
- summer solstice ( june 21)
- longest day of the year
What is the furthest point of the ecliptic circle to the south called?
- winter solstice (december 21)
- shortest day
What are the 2 points on the ecliptic where the sun crosses the celestrial equator are called ?
- equinoxes
- september 21 and march 21
- Vernal Equinox
- Autumnal Equinox
Which hemisphere do the seasonal names of equinoxes and solstices refer to?
- the seasons of the northern hemisphere
What is the zenith?
- 90 degrees above head
What is a white night?
- a night where it never gets completely dark
- high latitudes
- around december 22
What is a polar day?
- a period where the sun doesn’t set for 24 hours or more
- around june 21
When history states that they used the north star to navigate where they true?
- no
- because within 2500 years the north star has been in the same place but before then it was not even visible
What causes the motion of precession
- gravitational forces of the sun and the moon pulling on the earth as it rotates causes the earth to under -go a top-like motion called precession
- precession also causes the position of the north celestrial pole to slowly drift through the stars
Does the earths axis of rotation change direction?
- yes
- precession
What is a Synodic month
- new moon to new moon
- 29 1/2 days long
- the time it takes for the moon to orbit the earth with respect to the sun
Where does the moon get its light from and what is its orbit?
- the moon gets its light from reflecting off of the light from the sun
- the moons orbit is 29 1/2 days
- the moon orbits the the earth which orbits the sun
How long is a sidereal month
- the time it takes for the moon to orbit the Earth with respect to the stars
- 27.3 days long
Why are there sydonic months and sidereal months?
- because the earth moves in its orbit around the sun as the moon moves in its orbit around the earth
- aka they both have their own orbits
What are the phases of the moon
- waxing crescent: small slice of right lit up
- first quarter: right half lit, left hard dark
- waxing gibbous: sliver on left shadowed
- full moon: fully lit
- waning gibbous: small slice of right shadowed
- third quarter: left half lit, right dark
- waning crescent: small slice on left lit up
- new moon: completely dark, not visible from earth, directly between sun and earth
Do waxing or waning moons look bigger?
- waxing
Crescent vs Gibbous
- crescent: 1/4 moon visible
- gibbous: 3/4 visible
What are the three kinds of Lunar Eclipses?
What moon phase
- Penumbral: the moon appears dimmed
- Partial: part of the moons enters the umbra of the earth’s shadow is darkened
- Total: all of the moon enters the earth’s shadow and becomes a reddish color, only lit from light bending around the earth’s atmosphere
- happens 3-4 times a year in position of a full moon phase
What happens in Penumbral eclipses? (lunar)
- the moon fully enters the penumbra of the earths shadow (sun, earth then moon)
- appears dimmed
What happens in a Partial eclipse (lunar) ?
- part of the moon enters the umbra of the earths shadow
- the earth appears darkened
(sun, earth moon )
What happens in a Total Lunar Eclipse, what is unique about these ones?
- all of the moon enters the earth’s shadow and becomes a reddish color
- only lit from light bending around the earth’s atmosphere
Which kind of eclipses do you need to wear eyewear for?
- solar eclipse
What are solar eclipses?
What moon phase do they occur in
- solar eclipses occur at specific places on the earth
- only happens in New moon phase
- shadows become super sharp
- sun, moon, earth
What happens during a solar eclipse
- you start to feel a cold breeze as the heat from the sun is getting covered
- the moon looks black
- a solar corona becomes visible around the moon which is the sun’s atmosphere which we cannot usually see
- 1 1/2 to 2 1/2 minutes
- venus can been seen very high in the sky
When Is the next solar eclipse?
2026
What are the Three types of solar eclipses
- total solar eclipse
- if you are located where the umbra(shadow) of the moons shadow reaches you will see a total eclipse where the entire disk of the sun is covered by the moon - Partial solar eclipse
- those just outside this region where the penumbra of the moons shadow reaches will only see a partial eclipse during which only part of the sun is covered by the moon - Annular eclipse
- sometimes the occurs when the moon is too far away from the earth to completely cover the sun , when this occurs the moon appears in the centre and a thin ring or ‘annulus’ of light surround
When do eclipses occur
- they do not occur every full or new moon because the moons orbit is tilted by 5 degrees with respect to the earth’s sun ecliptic plane
- the eclipse shadow can miss the earth
- when the sun, moon and earth are aligned on the line of nodes
- every 18 years?
What is the line of nodes?
- 90 degree angle from the ecliptic plane
What is the lunar calendar?
- calendar that is based on the cycles of the moon phases
- examples. Islamic or Hijrah calendar
- year always consists of 12 lunar months
- there is an 11 day shift every year between solar and hirjah calendars
- most lunar calendars are lunisolar meant months are kept on a lunar cycle but then intercalary months are added to bring the lunar cycles into synchronization with the solar year
What are Solar Calendars?
The Gregorian calendars is the internationally accepted calendar
- pope gregory xiii on 24 feb 1582
Julian Calendar
What is a leap year?
- leap years add a 29th day to february which normally has 28 days.
- this is the differentiating feature between the Gregorian and julian calendar with a leap day every four years cuz gregorian omits 3 leap days during 400 year period
What year was a leap year in both the Gregorian and Julian calendars?
-1600, 2000
