Patterns in the Sky

Vocab for the textbook Understanding Our Universe by Stacy Palen and George Blumenthal 4th edition for Astronomy&101

Zenith

Point directly above the observer in the celestial sphere

Meridian

The line on the celestial sphere that runs from north to south dividing the sky into an eastern half and a western half

Horizon

The line that separates the sky from the ground. Perpendicular to zenith then spin 360 that’s your horizon

Celestial Sphere

Imaginary sphere with celestial objects in its inner surface.

Initially created by the Ancient Greeks

Constellation

Group of stars that seem fixed pattern on the celestial sphere

 

Day

Time it takes Earth to rotate on its axis.

A sidereal day is the time it takes for the Earth to complete one full rotation relative to distant stars, approximately 23 hours and 56 minutes.

A solar day, which is about 24 hours, measures the time from one noon to the next, accounting for Earth's orbit around the Sun.

Apparent Daily Motion

The daily path each object takes across the sky.

Altitude

The location of an object above the horizon or the angle formed between the object and the observer's line of sight, measured in degrees.

Latitude

The angular distance north or south from the equatorial plane of a nearly spherical body

Longitude

Circumpolar

Can always be seen from the horizon from a specific location on Earth, appearing to circle around the celestial pole.

Revolve

One object orbits another

Rotate

Spin on an axis

Ecliptic

The annual path of the sun against the stars; this follows the zodiac the 12 constellationsand is the basis for the changing seasons and the positions of celestial objects in the sky.

Summer Solstice

When the north pole is titled towards the sun, the day when the sun is the highest in the sky as it crosses the meridian, the sun rises farthest north of east, sets furthest north of west, marks the first day of summer typically on June 21

Winter Solstice

When the north pole is tilted away from the sun, resulting in the shortest day of the year, typically occurring around December 21.

Equinoxes

Twice a year when day and night are of approximately equal length, marking the beginning of spring and fall, typically occurring around March 21 and September 23.

Tropical Year

The time between equinoxes which is slightly shorter than 1 solar Earth orbit and is approximately 365.24 days long, marking the cycle of seasons.

Tropics

the regions of Earth located between the Tropic of Cancer and the Tropic of Capricorn (23.5 N and 23.5 S), the sun is directly overheard on the equinoxes

Precession of the Equinoxes

The change of the positon of the equinoxes over time due to the Earth's axial tilt and orbital motion, resulting in a gradual shift in the alignment of the stars as viewed from Earth.

Noon

The time at which the Sun crosses the meridian.

Equator

Imaginary line on Earth dividing it in half.

At the equator all stars rise and set each day.

At other latitudes, the celestial equator intersects the horizon due east and due west. Therefore, a star on the celestial equator rises due east and sets due west. Stars north of the celestial equator rise north of east and set north of west. Stars south of the celestial equator rise south of east and set south of west.

Tropical Year

The time between one crossing ot the vernal equinox and the next. Slightly shorter than the time it takes for Earth to orbit once about the sun.

New Moon

When the moon is between Earth and the sun.

Far side illuminated, from Earth its in darkness.

-UP AT DAYTIME.

• Up at daytime

• NEVER visible in night

• Rises with the sun at sunrise

• Crosses the meridian near noon

• Sets with the sun in the west.

Cresent

Phase in which the object appears less than half illuminated by the Sun

Gibbous

Phase in which the object appears more than half illuminated by the Sun

Waxing Crescent

• Moon visible east of the sun

• Most noticeable just after sunset, near the west

• Lit on the west side

First Quarter Moon

• 1 week after a new moon

• Named due to a fourth of its way through orbit

• Rises at noon

• Meridian at Sunset

• Sets as Midnight

Full Moon

• Opposite of the sun

• Viewed from Earth fully illuminated by the sun

• 2 weeks after the new moon

• Rises as the sun sets

• Meridian at midnight

• Sets at sunrises

Third Quarter Moon

• Half of the near side is in sunlight and half darkness

• Rises at Midnight

• Crosses meridian near sunrise

• Sets at noon

Eclipse

When the shadow of one astronomical object falls on another

Solar eclipse

When the Moon passes between Earth and the Sun casts a shadow on Earth.

• small shadow

Lunar Eclipse

• Moon is in the Earth’s shadow occurs when the Earth passes between the Sun and the Moon, causing the Earth’s shadow to cover the Moon.