Download Astronomy 101: Birth of Astronomy and Ancient Astronomical Discoveries - Prof. Rebecca A. and more Study notes Astronomy in PDF only on Docsity! AST114 Notes Birth of Astronomy Picture of the day: http://antwrp.gsfc.nasa.gov/apod/astropix.html Celestial Sphere: Imaginary sphere around the Earth on which objects in the sky reside. - Celestial Poles (Polaris) (when the north pole extends into the celestial sphere) - Celestial Equator Zenith: The point directly above your head. Horizon: Where the celestial sphere meets the ground. It goes 360 degrees around. ***The altitude of north pole will be equal to the altitude of the observer*** TERMS: Circumpolar zone: Area around the north/south celestial pole. Constellations: Star patterns – the sky is now broken into 88 sectors. Planets: Wanderers in the sky. Ecliptic: Apparent path of the sun through the stars. It is inclined at the 23 degrees due to the earth’s axis. Zodiac: 18 degree wide belt centered on the ecliptic. ***KNOW THE ZODIAC SIGNS: - Capricornus - Aquarius - Pises - Aries - Taurus - Gemini - Cancer - Leo - Virgo - Libra - Scorpius - Ophiuchus - Sagittarius ANCIENT ASTRONOMY Ancient astronomers knew the length of a year (365 days, adjusted every 4 years) Had calendars based on various stars Recognized common astronomical objects (there were 9 of them – not the planets) Understood the earth was spherical (Pythagoras – 500 BC and Aristotle – 350 BC) due to shadows on the moon and being able to see different stars during travels. Knew the sun was farther away than the moon due to solar eclipses Understood the moon’s phases Recorded new or guest stars CIRCUMPOLAR CONSTELLATIONS - Ursa major – big dipper - Ursa minor – little dipper – Polaris - Cassiopeia - Cepheus - Draco Eratosthenes – 200 BC: Measured the circumference of the Earth – not sure how close because of uncertainty of measuring system he used. Aristarchus – 260 BC: Aristarchus of Samos suggested that the Earth was moving around the sun, but his ideas were rejected due to observers not being able to observe any stellar parallax. Hipparchus – 150 BC: Defined and measured positions, direction and magnitude (brightness) of 850 stars; recognized the precession of the Earth’s axis. Ptolemy – 140 BC: Constructed a geometrical representation of the solar system using epicycles that predicted the position of the planets for any desired time and date; his epicycles were able to explain and predict Mars’ retrograde motion – Mars’ apparent backward motion through the stars. Nicolaus Copernicus – 1500 AD: Recognized as the father of modern astronomy. Proposed that the sun was the center of the solar system. Geocentric (earth entered) vs. Heliocentric (sun centered) models Galileo – 1600 AD: Galileo is credited with the beginning of modern science because of his experimental techniques – observations, testing, taking measurements, retesting, etc. He didn’t INVENT the telescope but made one from a description and used it to make astronomical observations. - Supported Copernicus’ view of the world - Discovered sunspots on the sun - Observed phases of venus - Described details of the Lunar surface - Discovered moons (4) of Jupiter which were the first things to be observed that did not go around the Earth - Found that the Milky way was composed of a multitude of individual stars. - Galileo wrote about the things he has discovered in the common language of the time. He
