astronomy chapter 2

Suppose that instead of being inclined to Earth's orbit around the Sun, the Moon's orbit was in the same plane as Earth's orbit around the Sun. In this hypothetical situation, approximately how many solar eclipses would occur each year?

12

In reality, the Moon's orbit about Earth is tilted (by about 5°) with respect to Earth's orbit about the Sun. As a result, the actual number of solar eclipses that occur each year is approximately _____.

2

There are 360∘ in a full circle: How many arcminutes are in a full circle?

21600 arcminutes

annular solar eclipse

A solar eclipse during which the Moon is directly in front of the Sun but its angular size is not large enough to fully block the Sun; thus, a ring (or annulus) of sunlight is still visible around the Moon's disk.

total solar eclipse

A solar eclipse during which the Sun becomes fully blocked by the disk of the Moon

partial solar eclipse

A solar eclipse during which the Sun becomes only partially blocked by the disk of the Moon.

Which of the following accurately describe an eclipse season?

During an eclipse season, there will be a lunar eclipse at full moon. During an eclipse season, there will be a solar eclipse at new moon. An eclipse season occurs when the nodes of the Moon's orbit are lined up with Earth and the Sun.

Based on what you have learned from your rankings in Parts A and B, why is it generally hotter in summer than in winter?

The Sun is higher in the sky in summer. We have more hours of daylight in summer

apparent retrograde motion

The apparent motion of a planet, as viewed from Earth, during the period of a few weeks or months when it moves westward relative to the stars in our sky.

totality

The portion of a total lunar eclipse during which the Moon is fully within Earth's umbral shadow or a total solar eclipse during which the Sun's disk is fully blocked by the Moon.

solar eclipse

When the moon passes directly between Earth and the sun, blocking sunlight from Earth

precession

a gradual wobble that alters the orientation of Earth's axis in space.

total lunar eclipse.

a lunar eclipse in which the Moon becomes fully covered by Earth's umbral shadow

What is a circumpolar star?

a star that always remains above your horizon and appears to rotate around the celestial pole

Which of the following celestial objects do NOT rise in the east and set in the west, as viewed from the Earth? (Assume that all of these objects are visible from your location on Earth, and that none of them are circumpolar.)

all objects

Eclipse seasons do not occur exactly twice a year. Instead, they occur slightly more often, coming about 173 days apart why do they do this, rather than occurring exactly twice each year?

because the line of nodes gradually moves around the Moon's orbit

farther north you notice more...

daylight in the summer and less daylight in the winter

What conditions must exist for a lunar eclipse to occur?

it must be full moon the Moon must be passing through Earth's orbital plane

Two stars that are in the same constellation:

may actually be very far away from each other.

LUNAR PHASES

memorize

winter solstice

occurs around December 21 and is the moment when the Northern Hemisphere receives the least direct sunlight.

summer solstice:

occurs around June 21, the moment when the Northern Hemisphere is tipped most directly toward the Sun and receives the most direct sunlight.

spring equinox

occurs around March 21 and is the moment when the Northern Hemisphere goes from being tipped slightly away from the Sun to being tipped slightly toward the Sun.

fall equinox

occurs around September 22 and is the moment when the Northern Hemisphere first starts to be tipped away from the Sun.

angular size=

physical size×360∘2π × distance

partial lunar eclipse

the Moon becomes only partially covered by Earth's umbral shadow

What conditions must exist for a solar eclipse to occur?

the Moon must be passing through Earth's orbital plane it must be new moon

angular size

the angle an object appears to span in your field of view

angular distance

the angle that appears to separate a pair of objects in the sky

Orion is visible on winter evenings in the northern hemisphere but not summer evenings because of

the location of Earth in its orbit.

penumbral lunar eclipse

the moon passes only within Earth's penumbral shadow and does not fall within the umbra

The ecliptic

the path the Sun follows as it appears to circle around the celestial sphere once each year. It crosses the celestial equator at a 2312∘ angle, because that is the tilt of Earth's axis.

lunar eclipse

when earth lies directly between the sun and the moon, so earth's shadow falls on the moon

The celestial equator,

which is a projection of Earth's equator into space, makes a complete circle around the celestial sphere.

longest shadow occurs in what season

winter