astrology Flashcards
what is the universe? where does this understanding come from?
the universe is all that exists everywhere, including all matter, energy, planets, stars, galaxies, and the space in which all of this exists. what we know and understand about the universe is based on who we are, where we live, what century we live in, and what culture we are from.
what sort of objects can we see in our skies? list them all
the sun, moon, stars, and planets (mercury, Venus, mars, Jupiter, and Saturn) along with comets, meteorites, novas and supernovas, and the Milky Way
how do we know that people in the past observed the movements and patterns of sky objects? what sort of evidence have they left us with?
people have made and left objects to show what they observed in the sky (drawings, sculptures, and monuments). they observe the movement of the sun and moon, and when solstices occur.
constellation
group of stars that form a pattern in the sky
how many constellations are there? give examples
88 known constellations (virgo, Hercules, Orion)
what is an asterism? give an example. how are they useful?
smaller groups of stars that form shapes within the constellation. the Big Dipper. they help to tell directions when compasses are not available.
celestial sphere
an imaginary rotating sphere on which lie all objects of the night sky. it extends around earth and is divided in to the northern and Southern Hemispheres (thus an observer can only see half).
ecliptic
path the sun and some other sky objects appear to take across the celestial sphere, due to earth’s orbit around the sun.
why do objects in the sky seem to move from east to west?
because of earth’s rotation
retrograde motion
makes planets appear to move across the sky, then loop back in the opposite direction
- due to earth going around the sun faster than the outer planets in the solar system
azimuth and altitude
azimuth: distance measured from the north along the horizon to a point below the celestial object
altitude: angular height of a celestial object measured from the horizon
the voyageur and its purpose
a spacecraft carrying gold-plated greetings, sights, and sounds from earth. purpose is to study outer planets
difference between optical telescope and radio telescope
radio telescopes can be used on cloudy days as well as at night because they detect radio waves, while optical ones only detect visible light (only detect small part of electromagnetic spectrum)
why are some telescopes placed in orbit above our atmosphere?
to observe space in more detail. (Ex/ only a fraction of electromagnetic radiation from space reaches earth’s surface. Therefore, some telescopes are in space to take advantage of the wealth of info the whole spectrum of this radiation provides).
how do telescopes that detect non-optical radiation contribute to our understanding of space?
from using them, we can determine what stars/planets are made up of and the radiation they give off.
galaxy
a collection of many billions of stars, plus gas and dust, held together by gravity. formed when a cloud of gravity, stars, and dust begins to contract.
what galaxy are we a part of?
The Milky Way (400 billion stars)
who discovered the first galaxy? when?
galileo discovered galaxies in 1610, but William Herschel discovered that the Milky Way is made of a collection of stars with his telescopes with his sister in 1780.
describe 3 types of galaxies
elliptical galaxies: - spherical to oval in shape
- older galaxies with few young stars
- 15-20 percent of all galaxies we see
spiral galaxies: - have a bulge in the centre and spiral arms on the sides
-70-75 percent of all galaxies
- have old stars in the centre and young stars on spiral arms
irregular galaxies: - have no definite shape and no spiral arms or central core
- 10 percent of all galaxies
star cluster
a collection of stars held together by gravity. open clusters have 50-1000 stars and appear around the Milky Way’s disk, and globular clusters have spherical shapes and 100000-1000000 stars
