Astronomy Chapter 0

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69 terms · Charting the Heavens

Spring Equinox

the Sun rises due east today, but will rise slightly north of due east tomorrow

Summer Solstice

noontime Sun reaches its highest point of the year; longest day of the yr

Fall Equinox

Sun has declination 0 degree today, but will have a negative declination tmrw

Winter Solstise

-Sun crosses the meridian 23.5 degrees lower in altityde than the celestial equator
-Sunset occurs at its farthest point south of due west for the year
-Noontime Sun casts the longest shadows

To indicate how far north or south we are on Earth, we specify location in degrees of

latitude.

latitude: there is a unique zero place called the ______ determined by the spinning of the Earth

equator

The closest terrestrial analog to hours of right ascension is the angle of

longitude

The solar day is 3.9 minutes longer than the

sidereal day

If you are in the Moon's umbral shadow, then you will witness a

total solar eclipse

The Earth's spin determines certain special locations on the Earth.
The spin ____ goes through the North and South Poles

axis

Midway between the North and South Poles, the _______ circles the Earth.

equator

What's the latitude of the North Pole?
Of the equator?

90 degrees North for the North Pole
0 degrees for the equator

A zero longitude place was arbitrarily chosen to be the longitude line that runs through _______, ________

Greenwich, England

Longitude lines can be numbered in a complete circle of __________,
(but we usually extend them only 180 degrees east of Greenwich and 180 degrees west of Greenwich)

360 degrees

For giving locations more precisely, degrees of latitude or longitude are subdivided into minutes

minutes of arc
60'

Each minute is further divided into 60 _______________

seconds of arc.

The Sun AND the Moon project an angular size of __ arc minutes on the sky.

30

From Earth, the Sun and Moon have about the same

angular diameter

the celestial sphere is divided into __ constellations

88

If Scorpius is now prominent in the summer sky, in 13,000 years it will be best seen

in the winter sky

When the Moon is directly opposite the Sun in the sky

Full Phase

the sun appears as a thin, bright ring

annular eclipse

Long ago, people believed that there was a giant sphere to which the stars were attached

celestial sphere

"celestial latitude lines"

declination

"celestial longitude lines"

right ascension

Unlike longitude, which is measured in degrees and minutes, right ascension is measured in

hours and minutes

An hour of right ascension corresponds to 60 degrees in the sky.

FALSE

A tropical year is the same as a sidereal year

FALSE

At the solstices, the Sun's declination will be _____ degrees from the equator

23.5

What angle would Eratosthenes have measured had Earth been flat?

0.00×100 degrees

If you are in the Earth's umbra, then it is

night time

Right ascension in the sky is very similar to latitude on the Earth.

FALSE

From the horizon to the observer's zenith is an angle of ___ for everyone on Earth

90°

The star Wolf 1061 has a parallax of 2.34 arcseconds, while the star Ross 652 has a parallax of 1.70 arc-seconds. What can you correctly conclude?

Wolf 1061 is closer to Earth than Ross 652

A lunar eclipse can occur only during the

full phase.

If the Moon's orbit were a little larger, solar eclipses would be

more likely to be annular

The seasons are caused by the precession of Earth's axis.

FALSE

The stars in a constellation are physically close to one another.

FALSE

The interval from new Moon to first quarter is about a

WEEK

The synodic month is

29.5 days

The 26,000 year cycle that changes the poles and equinoxes is called

precession

A solar eclipse can only happen during a:

new moon

If the Moon appears half lit, and is almost overhead about 6:00 AM, its phase is

third quarter

The twelve constellations the solar system bodies move through are the

signs of the zodiac

A long, thin cloud that stretched from directly overhead to the western horizon would have an angular size of

90°

You note that a particular star is directly overhead. It will be directly overhead again in

23 hours, 56 mins

While watching a star, you see it moves 15 degrees across the sky. How long have you been watching it?

1 hour

The parallax shift for all stars is

very small.

From the full moon to third quarter moon takes about

a week.

There is a solar eclipse of some kind every new moon.

FALSE

That Polaris will not always be the pole star is due to

PRESSESION SHIFTING THE CELESTIAL POLE

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. (Click "Show Moon with flat orbit" to see this situation.) 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

Earth orbits the Sun in the

ecliptic plane

What conditions must exist for a solar eclipse to occur?

Phase of the moon must be NEW and the Moon must be passing through the Earths orbital plane

What conditions must exist for a lunar eclipse to occur?

Phase of the moon must be FULL and the Moon must be passing through the Earths orbital plane

A Lunar Eclipse occurs when

Earth's shadow falls on the moon

If you could change the layout of the solar system, which of the following would cause a lunar eclipse to occur at least once every month in this hypothetical situation?

Change the moons orbital plane so that it is in the same plan eas the Earth's orbit around the SUn

If the earth rotated on its axis twice as fast as it currently does, but its
motion around the Sun stayed the same, then:

The night would be twice as long.

If new Moon fell on March 2nd, what is the Moon's phase on March 14th?

waxing gibbous

When the Moon is directly opposite the Sun in the sky, its phase is

full

The interval from new Moon to first quarter is about a(n)

week

The fact that the Earth has moved along its orbit in the time it took to rotate once is the reason for

the difference between solar and sidereal time.

At the equinoxes, the declination of the Sun must be ___ degrees

zero

Celestial coordinates specify which ______ something is with respect to Earth, but not the distance to the object

direction

For objects within the solar system (comets, planets, moons, asteroids), distance is often specified in

Astronomical Units (AU)

An AU is the average distance from the Earth to the Sun, which equals

149,597,870 kilometers

For objects outside the solar system, the______ is often used.

light year (ly)

One light year is equal to

63,240 AU.

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