Exam #1: Ch. 0, "An Introduction to Astronomy;" Ch. 1, "The Copernican Revolution"

At the equinoxes, what is the degree of the declination of the Sun?

0°

deci; d

10^-1 (0.1)

centi; c

10^-2 (0.01)

milli; m

10^-3 (0.001)

micro; μ

10^-6 (0.000001)

nano; n

10^-9 (0.000000001)

kilo; K

10^3 (1000)

mega; M

10^6 (1000000)

giga; G

10^9 (1000000000)

Zodiac Constellations

13 constellations that lie along the annual path of the sun across the sky: Capricorn, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Ophiuchus, Sagittarius

What is the rate of degrees per hour that Earth rotates on its axis?

15° per hour

What is the largest possible degree of longitude?

180°

If a particular star is directly above you, after how much time will it be there again?

23 hours and 56 minutes

At the solstices, how many degrees away is the Sun's declination from the equator?

23.5°

How many years are in Earth's precession?

26,000

Synodic/Lunar month

29.5 days; average period of the Moon's revolution with respect to the line joining the Sun and Earth; period of the Moon's phases, the Moon's appearance depends on the position of the Moon with respect to the Sun as seen from the Earth.

Tropical/Solar year

356.424; the time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth.

What is the greatest distance above or below the ecliptic the Moon can move?

5.2°

How many officially recognized constellations are there?

88

From the horizon to the observer's zenith is at what angle?

90°

What is the largest possible degree of latitude?

90°

Roughly how much time is between a full moon and a third quarter?

About one week

How were ancient astronomical and astrological studies related?

Astronomy and astrology were joined subjects, until astronomers recognized more concrete, scientific principles about the galaxy, and proved astrological concepts to be false.

Celestial Sphere

Imaginary sphere of gigantic radius with the earth located at its center; the poles of the celestial sphere are aligned with the poles of the Earth; the celestial equator lies along the celestial sphere in the same plane that includes the Earth's equator.

SI

International System of Measurement; system of physical units ( SI Units ) based on the meter, kilogram, second, ampere, kelvin, candela, and mole, together with a set of prefixes to indicate multiplication or division by a power of ten.

International Date Line; IDL

Imaginary line of longitude; 180° degrees east or west of the Greenwich Meridian.

Universe

The totality of space, time, matter, and energy, and "everything we are conscious of."

Annular Eclipse

"Ring of fire," occurs when the Moon moves in front of the Sun but does not cover the Sun's discs completely.

How much larger is the Sun than the Earth?

About 11 times.

Anti-Meridian

Also 180th Meridian: 180° east or west of the Prime Meridian with which it forms a great circle; used as the basis for the International Date Line.

Circumpolar Constellation

Always above the horizon, and always visible; located in the Northern Circumpolar sky.

Ecliptic

Apparent annual path of the Sun on the celestial sphere.

Why do constellations appear as though they are moving?

As Earth rotates, our position in relation to the constellations changes; therefore, it looks to us as though they are moving, when in fact, Earth is.

What causes the phases of the Moon?

As the Moon orbits the Earth, different parts of the side facing the Earth are illuminated by the Sun.

Nebulae

Clouds of dust and gas.

Significant Figures

Digits that carry meaning contributing to its measurement resolution. All non-zero numbers are significant; 'trailing zeros' that are not needed to hold the decimal point are significant, and zeros within a number are always significant; zeros that do nothing but set the decimal point are not significant.

Declination

Distance of a point north or south of the celestial equator; 'latitude for celestial objects.'

⊕

Earth

Star

Enormous mass/ball of hot gas; powered by nuclear reactions at its core.

Meridian

Geographical meridian or line of longitude that is half of the imagined circle of earth, connecting points of equal longitude, terminated by the North Pole and the South Pole; the position of a point along the meridian is given by its latitude.

Right Ascension

Goes eastward on celestial equator; moves on scale of 360° as point in sky moves east; 'longitude for stars.'

Constellation

Group of stars forming a pattern that is traditionally named after objects, animals, and mythological figures.

Open Cluster

Group of stars that appear close together.

Longitude

Horizontal, East or West

Vernal/Spring Equinox

Marks the beginning of spring in the Northern Hemisphere; the sun is at 23.5°

☾

Moon

Positive Declination

North of the celestial sphere

Scientific Method

Observations->Hypotheses->Theories-> Experiments->Measurements-->back to observations; continuous cycle

Jovian Planet

One of the four giant outer planets of the Solar System, they all have rings: Jupiter, Saturn, Uranus, or Neptune; names are based on Roman mythological figures (Jove was the Roman/Greek god of the sky, supreme mythological god).

Solar Eclipse

Only occurs at New Moon; occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks the Sun.

Zenith

Point directly above you, no matter your location.

North Celestial Pole

Point in the sky about which all the stars seen from the Northern Hemisphere rotate; Polaris is located almost exactly at this point in the sky.

South Celestial Pole

Point in the sky about which all the stars seen from the Southern Hemisphere rotate.

Celestial Equator

Projection of the terrestrial equator out into space; Earth's axial tilt inclines the celestial equator by 23.4° with respect to the ecliptic plane.

Non-Circumpolar Constellations

Rise in the east, fall in the west; visibility varies with the rotation of the Earth and Earth's position in orbit.

Scientific Notation

Scientists use this method of measurement to handle very large or very small numbers; works in powers of ten; Physics includes very small and very large numbers frequently.

Messier Objects

Set of astronomical objects first listed by French astronomer Charles Messier ( in his"Catalogue des Nébuleuses et des Amas d'Étoiles," or "Catalogue of Nebulae and Star Clusters," 1771); First edition covered 45 objects numbered M1 to M45; his final list had 103 objects; other objects were added later by other astronomers, and the last object, M110, was added in 1966.

Negative Declination

South of the celestial sphere

Globular Cluster

Spherical collection of stars that orbits a galactic core as a satellite; very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers.

☉

Sun

Galaxies

Swarms of billions of stars (Ex.: Milky Way, which has 3 to 4 billion stars).

Powers of Ten

Ten multiplied (when +) or divided (when -)by itself a certain number of times.

Why aren't there lunar and solar eclipses every month?

The Moon's orbit is inclined to the ecliptic, meaning that the tilt of the Moon's orbit makes the Moon not line up with Earth and the Sun every time in all three dimensions.

Parallax

The apparent displacement of a foreground objective, relative to observers location to an object.

Polaris

The brightest star in the constellation Ursa Minor; it is above the north celestial pole, and is the current 'Northern Pole star;" from the perspective of someone on Earth, this star does not change location as Earth rotates.

Light Year

The distance traveled by light in one year; regular measures of time, like minutes or hours, are too small to describe the distance.

How does the size of a parallax shift relate to closeness of the object?

The larger the parallax shift, the closer an object is.

How does the parallax of a nearby object compare to that of an object farther away?

The nearby object exhibits a larger parallax than the farther object; inversely related to distance.

Why does Polaris very gradually move

The precession of the Earth shifting the celestial pole

Astronomy

The study of the universe.

Sidereal day

The time it takes for the Earth to complete one rotation about its axis with respect to the 'fixed' stars; 3.9 days shorter than solar day--the position of the sun makes the difference.

Solar day

The time it takes for the Earth to rotate about its axis from one sunrise or sunset to the next (sunrise to sunrise, sunset to sunset)

From the perspective of Earth, how do the angular diameter of both the Sun and the Moon compare?

They look similar or the same; ~ 0.5o = 30 arcmin; in reality the Sun's physical diameter is 400 times bigger than the Moon, while the Moon is ~ 400 times closer to the Earth

Physical Quantities

Time, Mass, Speed, Length (Exs.: Metric System, SI/Standard or British System, etc.)

In which direction does the Earth rotate?

To the East.

SI Prefixes

Used to form decimal multiples and sub-multiples of SI units.

Latitude

Vertical, North or South

How large are the parallax shifts of stars?

Very small.