Charting the Heavens

Warm-up 9/15 Which constellation has the brightest star in the sky?

Galaxy and the Universe The universe is the totality of all space, time and matter The universe is constantly growing Our galaxy is the milky way, and it spans 100,000 light years

Celestial Sphere Formed from the apparent rotation of stars based on the earths spin Consists of the North Celestial Pole, celestial equator, and south celestial pole While technically incorrect, it gives us a way to better map the stars Use “angular positions” to find locations of the stars

Motion of Sun and Stars The basic social time unit is called a Solar Day, a 24 hour period The passage of the sun, as well as other objects is called Diurnal motion

Sidereal day This is a day based on the rotations of the stars This is different from a solar day because it is based not only on the earth’s rotation around the sun, but on the earth revolving around its own axis The solar day is 3.9 minutes longer than the sidereal day

Seasonal Changes The earth is tilted at about 23.5 degrees, which allows for what we know as seasons At certain times of the year, certain parts of the earth get more/less sunlight, which changes the length of days and the average temperatures in the area

Seasonal Changes

Warm-Up 9/16 What is the difference between a sidereal and solar day?

Solstices These occur on the day when the earth is tilted the most When the one side of the earth experiences cold weather, the other side of the earth experiences hot weather Summer solstice: June 21st, longest day of the year for the Northern hemisphere Winter Solstice: December 21; shortest day of the year for the Northern Hemisphere

Equinox When the earth intersects the celestial equator we have an equinox There are fall and vernal(spring) equinox

The Moon Completes phases in about 29 days Consists of “waxing” and “waning phases”

Moon Phases Waxing phases consist of the moon getting brighter Waning phases consist of the moon getting darker These go together with gibbous and crescent phases

Moon Months 2 types of months: Sidereal month: The time it takes for the moon to complete one revolution around the earth (27.3 days) Synodic Month: The time it takes for the moon to complete it’s phases (29.5 days)

Lunar Eclipse A lunar eclipse occurs when the earth blocks all sunlight to the moon You can have 2 types of Lunar Eclipses; Partial and Total Partial is an imperfect alignment between the sun, earth and moon but still occurs Total is a perfect alignment Can be seen by the whole entire night side of earth

Solar Eclipse When the moon blocks out the sun Again, there are partial and total eclipses Can only be seen by a small portion of the earth, unlike a lunar eclipse

Warm-up 9/21 What is the difference between an equinox and a solstice?

Triangulation Using Trigonometry to find the location of certain objects

Parallax a displacement or difference in the apparent position of an object viewed along two different lines of sight

Kepler’s first law All planetary orbits are ellipses

Kepler’s second law a line between the sun and the planet sweeps equal areas in equal times

Kepler’s third law The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit. Py2 = aAU3

Warm-Up 9/22 What is so important about today?! (hint: it has to do with the earth’s tilt)