AST 115 1st EditionExam # 1 Study Guide Lectures: 1 - 11Lecture 1 (January 14)Introduction to Astronomy (basics to know):- Why do astronomers use the powers of ten notation (scientific notation)? Astronomers use the powers of ten notation in order to study distances and sizes of objects that vary from extremely small (i.e. atoms) to very large (i.e. galaxies; the universe). This helps astronomers to avoid using terms such as “a billion trillion”.-How is the powers of ten notation used? The formula used for the powers of ten notation is ± a .bc ×10± dThe “a” in the equation represents a number between one and ten. The “bc” in the equation represents a figure ranging from 00 to 99. The exponent “d” in the equation represents any integer. If the calculated number is large, exponent “d” will be positive. If the calculated number is small, exponent “d” will be negative. For example, in scientific notation, the number 0.0000000067 would be written as 6.70 ×10−9 because we moved the decimal to the right nine spaces.- What is an Astronomical Unit (A.U.)? An astronomical unit is the average distance between the Sun and the Earth. One astronomical unit is approximately 150,000,000 kilometers (1.50 ×108 km) or 93,000,000 miles (9.30 ×107mi).Astronomers use astronomical units to measure distances to objects in our solar system.Overview of the Metric System:-What do we mean by the “size” of an object? When we are measuring the size of an object, we mean that we are looking for the distance across an object. - Basic conversions:1 m = 1 yd (about 40 in)1 km = 1000 m (about 0.6 mi)1 cm = 0.4 in1 mm = 0.039 in-What is mass? Mass is how much material an object contains. It is measured in kilograms (kg). One kilogram is equal to about 2.2 pounds. However, mass and weight are NOT the same thing. Weight depends on where the object is in space. An object on the surface of the Moon will have about 1/6 the weight on Earth, but it will have the same mass.Introduction to Chapter 1: Discovering the Night Sky- There are several things we think we see in the night sky, but many of them turn out just to be illusions. One illusion you may notice is that the night sky seems to be filled with apparent patterns of stars called “constellations”. These stars appear to be, but are NOT all the same distances from us. These stars have angular separation, but not physical separation (distance). - How are the stars named? There are given names for the brightest stars in the constellations (Vega, Regulus, Betelgeuse…). There are also Greek letter designations for the brightest and intermediately bright stars (alphaLyrae, alpha Leonis, alpha Orionis…). Finally, astronomers use catalog numbers for the brightest stars, intermediately bright, and dimmer stars (HR 7001, HD 39801…).Lecture 2 (January 16)Chapter 1 continued:- List and describe the illusions in the night sky that we discussed in class.1. The night sky seems to be filled with apparent patterns of stars called “constellations”. (Previouslymentioned and explained in lecture 1).2. The Celestial Sphere (CS): When observing the night sky, a person seems to be at the center of a vast dome/sphere with a black or grey interior. Astronomers use this imaginary grid to establish directions and bearings in for celestial objects when their distances are unknown or unimportant.Within the Celestial Sphere is the Celestial Equator (CE). The Celestial Equator is the imaginary line on the Celestial Sphere directly above the Earth’s equator that divides the sky into northern and southern hemispheres. The North Celestial Pole (NCP) is the imaginary point just about Earth’s North Pole. The South Celestial Pole (SCP) is the imaginary point directly above Earth’s South Pole. 3. The Celestial Sphere appears to rotate around the Earth (going west) once in 24 hours. This causes the Sun, moon, planets, and stars to appear to rise in the East, and set in the West. However, all of this is just an illusion caused by the Earth’s rotation towards the east.4. The annual apparent eastward motion of the Sun along the Celestial Sphere. The cause of this illusion is the Earth revolving around the Sun. The Sun’s annual path on the CS is called the Ecliptic. The Sun also appears to move through “Constellations of the Zodiac” along the Ecliptic. The annual motion of the Earth also causes the stars to rise about four minutes earlier each night.This is the annual “Parade of Constellations”.- Explain the Constellations of the Zodiac There are 12 to 13 constellations centered on the ecliptic. The Sun spends about one month at each of the constellations, which is why there are certain constellations that can only be seen during certain seasons. - Why is it that the bright planets can always be seen within the boundaries of the Zodiac? The orbits of the planets are nearly in the same plane of the ecliptic.- What is the Equatorial Coordinate System? Astronomers use the equatorial coordinate system to keep track of the positions of objects in the sky. They imagine the celestial sphere surrounding Earth, along with Earth’s equator extending into the sphere. Declination describes where an object is between the two poles located on the imaginary celestial sphere (similar to latitude on Earth). Right ascension is the angular distance from a primary direction along the celestial equator (similar to longitude on Earth).- Describe the daily paths of objects in the sky at the North Pole and the Equator on Earth. These daily paths depend on your latitude on Earth. At the North Pole, all objects in the sky movein paths parallel to the horizon (altitude of NCP = 90˚). At the equator, all objects rise and set perpendicular to the horizon (altitude of NCP = 0˚).Lecture 3 (January 21)- How do you measure your latitude? Measure the altitude of Polaris above your northern horizon. Your latitude will equal the altitude of the North Celestial Pole.- What are Circumpolar Stars? Circumpolar stars are stars that go around the poles. They never rise and never set. (At the north and south poles, the entire sky is circumpolar. At the equator, none of the sky is circumpolar).- What causes the changing of the seasons on Earth? The changing of the season is due to the fact that Earth’s rotational axis is tilted about 23.5˚ [The changing of the seasons NOT due to the distance of the Earth from the Sun; it is also NOT