T1: Lec 5-6 Flashcards
(19 cards)
waht is an eclipse? waht types are there?
occur when one celestial body covers another
Lunar - Earth casts a shadow on the moon
Solar - moon casts shadow on earth
how do we know the Earth is round?
shape of earth’s shadow on moon is round, ships pass over horizon, and changin stars in the sky as you sail
What are the visible planets? and who was the first heliocentric proposal made by?
Mercury, Venus, Mars, Jupiter, and Saturn
Look like stars (Venus and Mercury are morning and evening stars
1st heliocentric proposal by Aristarchus of Samos
What is retrograde? how does it relate to Mercury and Venus? or a Heliocentric solar system?
the pattern of a planet’s movement in the sky when a planet over takes it
Geocentric idea would crux on the planets fully circling overhead
Venus and Mercury are NEVER behind earth (never on opposite sides of the sky)
who is Copernicus?
(1473-1543): Heliocentrist - introduced ellipticals
Copernican Revolution: figure shape of solar system, birth of science in the west, religious tension, established observation and experiment (Scientific method)
who is tycho Brahe?
Tycho Brahe: Last naked eye astronomer
First to make a very precise observation that measured star and planet distances “Great equatorial armillary) = 3 m in diameter!
who is Kepler?
Kepler: Tyche’s Assistance
Established planets move in ellipses, established 3 Laws of planetary motion:
Planets move in ellipses
Equal areas in equal times
Cube-square law of periods
Who is isaac newton?
Explained WHY planets move in ellipses through gravity
Laws of Motion, theory of gravity, Theory of everything, calculus, etc.
What is parallax? What is it able to measure?
the displacement of an object according to different perspectives
Parallax is able to measure distances, form the base of the cosmic distance ladder, allow the study of proper motion and radial velocity (movement towards or away from us).
What phenomena show parallax?
Transit of Venus - from two different perspectives, the position of Venus is different
Solar eclipse - the position of two different perspectives either gives a full eclipse or only partial eclipse
What is adaptive optics?
We can take measurements using lasers pointed at the moon and reflected back to measure distance. (adaptive optics)
What are Parallax limitations?
Limitations of Parallax are that parallax is only most effective for measuring distances of nearby stars as the angle is too small to accurately measure further objects, and the further star the smaller the angle, and thus the less precise the distance measurement will be.
What is stellar parallax?
nearby stars move in relative to the background stars, caused by the Earth’s movement around the sun
The further the star’s distance = less parallax (smaller)
What is Baseline Parallax? Give an example of what we use:
distance between observations (e.g. eyes)
Diameter of earth’s orbit (2AU), serves as a baseline for measuring the parallax angle (the small angle created at a particular point when straight lines from its extremities are joined)
What is a parsec?
A star that is 10 parsecs away = resolution of ….?
The distance of a star relative to arcseconds (a star that is 3.26 light years away = 1 arcsec)
A star that is 10 parsecs away = resolution of 0.1 arcsec
A star that is 0.7 arcsecs away from earth. How many arcsecs is it from Pluto, which is 35x further away from earth.
0.7 * 35 = 24.5 arcsecs from pluto
What does AU mean?
AU - astronomical units
the mean radius of Earth’s orbit around the sun used as measurement
How can we measure apparent distances?
We can measure apparent distance from brightness using “cosmic distance ladder” and “standard candles”
