Ast101 midterm 1

What are some reasons for why we experience the phases of the moon?

Half of the moon Is always facing the Earth but is illuminated differently by the Sun at all times

What are constellations?

Constellations are patterns in the night sky that are 88 sectors of division in the night sky. They are fixed relative to each other but rise and set every night

When does a lunar eclipse occur?

A lunar eclipse occurs when the Earth’s shadow falls onto the moon.

Solar eclipses, when do they occur ?

They usually occur on a very narrow path on Earth’s surface

they occur when from the earth, the moon covers the sun’s light.

This casts a shadow on the earth

Kepler’s law 1

The planets move around the sun in an elliptical shape, with the Sun at one focus

Kepler law 2

A planet orbiting around the Sun covers equal areas of distance over equal intervals of time, moving faster as it approaches the sun. Planets further away from the Sun move slower

Kepler law 3

There is a mathematical equation that finds out how long 1 year is on one planet relative to earth time by measuring its speed

What is the difference between a comet and an asteroid?

Asteroids are mainly located in the Asteroid belt between Mars and Jupiter. They have a lower eccentricity than comets and are much closer to the sun.

Comets have higher eccentricity and orbit and speed up as they approach parhelion. They are found all over the solar system

They are both leftover materials from the formation process of the solar system

What are some differences between terrestrial and jovian planets?

Terrestrial planets : Mercury, Venus, Earth, and Mars (my very edgy mother)

• not as many moons

• thin atmospheres

• rocky surfaces

• made from heavy elements

jovian planets: Jupiter, Saturn, Uranus, Neptune (just sharted under Napoleon)

• many moons

• typically larger

• move slower

• thicker atmospheres

• gas giants +ice planets

What is eccentricity?

Eccentricity is the ratio of distance from the foci of an ellipse to the length of the major axis. the smaller it is, the more round the ellipse shape is

Problems with the geocentric model of the universe

• Galileo discovered the moon has craters, which corrupted the idea that everything in the heavens was perfect

• Retrograde motion could better be explained by noting that Mars does not just rotate in epicycles around the earth

• Jupiter has moons that orbit it (not everything in the heavens revolves around earth )

• Venus appears to change in sizes throughout the year which could not be possible if it was orbiting earth

Distances of things in our Solar system from Shortest to longest

earth to the moon

The Sun to Mercury

the sun to earth (1 AU or 150 million km )

the sun to Jupiter

1 light year ( 9.46 trillion km)

the sun to Proxima Centauri (4.5 light years away )

the sun to the centre of the Milky Way galaxy

the sun to Andromeda

Distinct planets

• Jupiter has many moons

• Mercury has no moons

• Venus has an extremely thick co2 atmosphere (high temperatures)

• Venus also spins on its axis in retrograde (clockwise)

• Mars has dry ice and many probes/ landers

• Mars has a 25.2 degree orbital tilt which produces significant seasons

• Jupiter has a thick gaseous atmosphere and a giant ball of liquid hydrogen at its centre

• cannot be observed directly

• Saturn has rings, second largest planet in solar system (several probes have visited) has moons orbiting its rings

• Uranus is the coldest planet and is made of thick water, ammonia and methane w a 98 degree axis tilt and thin rings

• Neptune has the strongest winds in solar system, is the slowest planet (furthest from the sun)

the zodiac

The planets, sun and moon are all found within an 18 degree wide belt that is entered around the ecliptic

What happens on the Summer solstice in the northern/southern hemisphere?

• The Sun goes to the highest point in the sky at the Tropic of Cancer

• The day is the longest of the year

• The suns rays illuminate the North Pola for 24h

• The Arctic circle (place 67 degrees north of equator) is lit up

Southern hemisphere

• All places within 23 degrees of the South Pole (called Antarctic circle) do not see the sun for 24 hours

What happens on the winter solstice (December 21) in the Northern and Southern Hemispheres?

Northern Hemisphere

• The Arctic circle does not experience any sun for 24 hours

• the northern hemisphere experiences the lowest amount of daylight

• the sun rises in the sky for less time/ appears lower than the zenith

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Southern Hemisphere

• the antarctic circle receives 24 hours of sun

• the tropic of capricorn experiences the sun at the zenith at noon

• all places within 23 degrees of the South Pole experience sun 24 hours

What happens on the fall +vernal equinox

• the sun crosses the equator

• there is 12 hours of day and 12 hours of night

• the sun is on the celestial equator and does not favour either hemisphere

How does the equator experience seasons?

• temperature wise, everything is very similar

• seasons are characterized by the moisture rain etc

When does the new moon occur?

When it is in the same general direction in the sky as the sun

the dark side is turned toward us

• it is the beginning of the moon cycle

• the glare of the sun washes it out (embarrassing)

• rises at sunrise, sets at sunset

phases of the moon + times they rise and set

Moon rises and sets a little bit later with each phase, with its highest peak in between

New moon

• ( day 0) —> rises and sets at sunrise +sunset

Waxing crescent

• (3-4 days after new moon) —> transits/rises/sets 3 hours after sun

1st quarter

• (1 week after new moon)—> transits/rises/sets 6 hrs after sun i

Waxing gibbous

• (10-11 days after new moon) —>transits/rises/sets after sun

Full moon (2 weeks after new moon)

• The earth is between the moon and sun at this point

• Only time lunar eclipse can occur

• Rises at sunset, sets around sunrise

Waning gibbous

• Rises around 3 hours after sunset (9am) sets around (1am) transits 9h before sun, sets 3hrs after sun

3rd quarter (around a week before next new moon)

• transits/rises/sets 6 hours before sun

• rises around midnight, up the rest of night and morning

Waning crescent (2-4 before new moon)

• transits/rises/sets 3 hours before sun

this is only true around the equinox so

Why does solar eclipse happen?

• When moons orbit is tipped relative to the ecliptic plane, as new moon crosses the ecliptic plane and blocks the light from the sun

How long is the moon cycle?

around 27 earth days

What would seasons be like on a planet w a diff axial tilt than earths?

• Planet with a greater tilt would have more pronounced seasons

• Planets with a smaller tilt would have no significant seasons

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True facts about celestial bodies as theyre viewed on Earth

• Venus has phases just like the moon

• mars has gibbous looking phases

• all planbets outside of earths orbit can only exihibit nearly full phases

why don’t we see an eclipse at every full moon?

because the moon is tilted about 5 degrees relative to the earths orbital tilt and this causes the suns shadow to just miss the line where it needs to go to cast a shadow