Celestial Mechanics Study Guide

These flashcards cover various concepts related to celestial mechanics and astronomy, including the celestial sphere, coordinates, eclipses, and lunar phases.

Celestial Sphere Model

A representation of the sky where stars and planets are projected onto an imaginary sphere surrounding the Earth.

Limitations of the Celestial Sphere Model

The model inaccurately represents distances between celestial objects and does not account for their three-dimensional positions.

Celestial Coordinate System

A system used to specify the locations of celestial objects, defined by right ascension and declination.

Celestial Coordinates for Vega

Vega has the coordinates approximately 18h 36m 56.33s right ascension and +38° 47' 1.28'' declination.

Degrees of Sky from Horizon to Horizon

The sky visible from horizon to horizon is approximately 180 degrees.

Celestial Equator

An imaginary projection of Earth's equator onto the celestial sphere.

Celestial Poles

The points where Earth's axis of rotation intersects the celestial sphere, considered as the North and South celestial poles.

Ecliptic

The apparent path of the Sun across the celestial sphere, marking the plane of Earth's orbit.

Tilt of the Ecliptic

The ecliptic is tilted at an angle of about 23.5 degrees with respect to the celestial equator due to the tilt of Earth's rotational axis.

Objects Following the Ecliptic

The Sun, Moon, and planets follow the path of the ecliptic.

Zodiacal Constellations

A group of constellations through which the Sun, Moon, and planets appear to move, significant in astrology.

False

True or false: stars in a constellation are actually next to each other in space.

Daily vs. Yearly Motion T-chart

Daily motion refers to the apparent movement of celestial objects due to Earth's rotation, while yearly motion refers to the orbit of Earth around the Sun.

Rotation

The spinning of Earth on its axis, causing day and night.

Revolution

The orbiting of Earth around the Sun, which takes about one year.

Causes of Seasons

Seasons are caused by the tilt of Earth's axis and its orbit around the Sun, leading to varying sunlight intensity and duration.

Sun's Position above the ecliptic

The Sun is highest above the ecliptic at the summer solstice and lowest at the winter solstice.

Altitude Change with Seasons

The Sun's altitude varies with seasons; higher in summer and lower in winter affecting sunlight distribution.

Solstices and Equinoxes

Solstices occur during the longest and shortest days, while equinoxes occur during equal day and night; they affect sunrise and sunset positions.

Direction of Rising and Setting

Planets, the Moon, and stars generally rise in the east and set in the west.

Stars Rise Earlier

Stars rise about 4 minutes earlier each night due to Earth's orbit around the Sun.

Sidereal Day vs. Solar Day

A sidereal day is based on Earth's rotation relative to distant stars, about 23 hours and 56 minutes, while a solar day is based on the Sun's position, 24 hours.

Star Rising Time

If a star rose at 9:57 PM tonight, it will rise at approximately 9:53 PM tomorrow.

Phases of the Moon

The phases include new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent.

Waxing vs. Waning

Waxing refers to the moon's illumination increasing, while waning refers to its illumination decreasing.

Half Moon Phase

A 'half moon' can refer to either the first quarter or last quarter phase.

Sidereal Month vs. Lunar Phases

A sidereal month is the time the Moon takes to orbit Earth relative to the stars, roughly 27.3 days, while a full set of lunar phases takes about 29.5 days.

Solar Eclipse

An event where the Moon passes between Earth and the Sun, blocking the Sun's light.

Position During Solar Eclipse

In a solar eclipse, the Moon is between the Sun and Earth.

Annular vs. Total or Partial Solar Eclipse

An annular eclipse occurs when the Moon is too far from Earth to completely cover the Sun, whereas a total eclipse completely covers it.

Lunar Eclipse

An event where Earth comes between the Sun and the Moon, casting a shadow on the Moon.

Position During Lunar Eclipse

In a lunar eclipse, Earth is between the Sun and the Moon.

Color of Moon During Lunar Eclipse

The Moon appears red during a lunar eclipse due to Earth's atmosphere filtering sunlight.

Eclipses Frequency

Eclipses don't happen every month due to the tilt of the Moon's orbit.