Term
| Give some insight on viewing the curved scale on page 7. |
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Definition
The curved scale summarizes the range of sizes from atomic particles up to the diameter of the entire universe visible.
Distances traveled on the curved scale (no matter where you start or end, so long as you travel the same distance on the scale) give proportionally the same distance between the two pairs of objects.
In other words, the size difference between a proton and an atom is proportionally the same as the difference between an astronomical unit and the distance to the nearby stars; they take up the same amount of space on the scale. |
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Term
| A light year is the distance light travels in a year through a vacuum. What is this distance in km and AU? |
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Definition
| 1 ly = 9.46 x 10^12 km = 63, 000 AU |
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Term
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Definition
| A light minute is the distance light travels in a vacuum in one minute; approximately 18 million kilometers. |
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Term
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Definition
A parsec is the distance at which two objects separated by 1 AU make an angle of 1 arcsec.
1 pc = 3.09 x 10^13 km = 3.26 ly |
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Term
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Definition
| A constellation is any of the 88 contiguous regions that cover the entire celestial sphere, including all the objects in each region; also, a configuration of stars often named after an object, a person, or an animal. |
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Term
| How does the celestial sphere appear to move with relation to the Earth? |
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Definition
| The celestial sphere appears to revolve around Earth once in each day-night cycle. In fact, it is Earth's rotation that causes this apparent motion. |
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Term
| How are the celestial poles and equator determined? |
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Definition
| The poles and equator of the celestial sphere are determined by extending the axis of rotation and the equatorial plane of Earth out onto the celestial sphere. |
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Term
| What is the ecliptic plane? |
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Definition
| From day to day, the Sun traces a straight path on the celestial sphere. This path is called the ecliptic. |
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Term
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Definition
| The zodiac are the constellations through which the Sun moves throughout the year as it travels along the ecliptic. |
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Term
| Describe all the equinoxes and solstices. |
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Definition
Equinox: This is when the ecliptic and the celestial equator intersect. This happens twice a year and results in 12 h of daytime and 12 h of nighttime. One is called Autumnal and the other is called vernal.
Winter solstice: This is the point on the ecliptic farthest south of the celestial equator. The Sun rises to the lowest height at noon. This is the fewest hours or daylight for the norther hemisphere.
Summer solstice: The Sun rises farthest north of east and passes highest in the sky. The northern hemisphere experiences the most daylight. |
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Term
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Definition
| The seasons result from the tilt of the Earth's rotation axis combined with Earth's revolution around the Sun. |
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Term
| What causes the phases of the moon? |
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Definition
| The phases of the Moon are caused by the relative positions of Earth, Moon, and Sun. The Moon completes one cycle of phases in a synodic month, which averages 29 1/2 days. |
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Term
| Describe the lunar eclipse. |
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Definition
| A lunar eclipse occurs when the Moon moves through Earth's shadow. During a lunar eclipse, the Sun, Earth, and Moon are in alignment with Earth between the Sun and the Moon, and the Moon is in the plane of the ecliptic. |
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Term
| Describe the solar eclipse. |
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Definition
| A solar eclipse occurs when a strip of Earth passes through the Moon's shadow. During a solar eclipse, the Sun, Earth, and Moon are in alignment with the Moon between Earth and the Sun, and the Moon is in the plane of the ecliptic. |
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Term
| Describe the scientific method. |
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Definition
| Science is process for gaining more knowledge in a way that ensures that the information can be tested and thereby accepted by everyone. Science as a process is also called the scientific method, and it describes how scientists ideally go about observing, explaining, and predicting physical reality. |
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Term
| Describe Ptolemy's geocentric theory. |
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Definition
| According the Ptolemy, each planet is assumed to move in a smal circle called an epicycle, the center of which moves in a larger circle called a deferent, whose center is offset from Earth. This was his attempt to account for the occasional retrograde motion of the planets and the resulting loops that the planets trace out against the background stars. |
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Term
| Aristarchus came up with a heliocentric cosmology for what reason? |
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Definition
| Aristarchus proposed a more straightforward explanation of planetary motion, namely, that all of the planets, including Earth, revolve around the Sun. The retrograde motion of Mars in this heliocentric (Sun-centered) cosmology occurs just because the faster moving Earth overtakes and passes the red planet. |
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Term
| Who was Nicolaus Copernicus? |
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Definition
Copernicus developed a heliocentric theory of the known universe. He determined which planets are closer to the Sun than Earth and which are farther away.
His revolutionary theory was flawed in that he assumed that the planets had circular orbits around the Sun. |
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Term
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Definition
Tycho reasoned that if a new star is nearby, its position should shift against the background stars over the course of a night. This is the concept of parallax.
Also, Tycho rejected both Copernicus's heliocentric theory and the Ptolemaic geocentric system. He devised a halfway theory called the Tychonic system. According to Tycho's theory, Earth is stationary, with the Sun and Moon revolving around it, while all the other plants revolve around the Sun. |
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Term
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Definition
Kepler developed three laws that describe orbital shapes, changing speeds, and the lengths of planetary years.
1. The orbit of a planet around the Sun is an ellipse with the Sun at one focus.
2. A line joining a planet and the Sun sweeps out equal areas in equal intervals of time.
3. The sqaure of a planet's sidereal period around the Sun is directly proportional to the cube of the length of its orbit's semimajor axis. |
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Term
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Definition
Galileo made two discoveries using telescopes that supported a heliocentric cosmology:
1. Phases of Venus
2. Moons orbiting Jupiter |
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Term
| What is Newton's theory of gravity? |
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Definition
Newton's law of gravity:
Two objects attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
In other words, gravitational force decreases with distance. |
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Term
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Definition
Light sometimes acts acts as particles (not just waves), creating what is called the wave-particle duality.
Einstein proposed that light travels as waves enclosed in discrete packets, now called photons. |
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Term
| What is the electromagnetic spectrum? |
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Definition
| This is the full range of possible wavelengths. |
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Term
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Definition
| A wavelength (lambda) is the distance between two successive wave crests. |
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Term
| What is a reflecting telescope? |
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Definition
| Reflecting telescopes, or reflectors, produce images by reflecting light rays from concave mirrors to a focal point or focal plane. |
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Term
| What is a refracting telescope? |
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Definition
| Refracting telescopes, or refractors, produce images by bending light rays as they pass through glass lenses. Glass impurity, opacity to certain wavelengths, and structural difficulties make it inadvisable to build extremely large refractors. Reflectors are not subject to the problems that limit the usefulness of refractors. |
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Term
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Definition
| Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. |
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Term
| What effect does Earth's atmosphere have on different types of light? |
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Definition
| Earth's atmosphere is fairly transparent to most visible light and radio waves, along with some infrared and ultraviolet radiation arriving from space, but it absorbs much of the electromagnetic radiation at other wavelengths. |
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Term
| What is an ideal blackbody? |
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Definition
| And ideal blackbody absorbs all of the electromagnetic radiation that strikes it. |
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Term
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Definition
Wie's law:
The peak wavelength of radiation emitted by a blackbody is inversely proportional to its temperature.
In other words, the hotter any object becomes, the shorter its lambda-max, and vice versa. |
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Term
| How do spectral lines help with element finding? |
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Definition
| Spectral lines serve as distinctive "fingerprints" that identify the chemical elements and compounds comprising a light source. |
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Term
| What is an atom and what do atoms mean to spectral lines? |
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Definition
An atom consists of a small, dense nucleus (composed of protons and neutrons) surrounded by electrons. Atoms of different elements have different numbers of protons, while different isotopes have different numbers of neutrons.
The spectral lines of atoms of a particular element correspond to the various election transitions between levels of those atoms. When an electron shifts from one energy level to another, a photon of the appropriate energy (and hence a specific wavelength) is absorbed or emitted by the atom. |
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Term
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Definition
| The Bohr model depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity. |
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Term
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Definition
1. Emission lines are the spectral lines from a flame against a dark background. The number of lines produced and their colors are unique to the element or compound that produces them.
2. A bright line of electromagnetic radiation. |
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Term
| What are absorption lines? |
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Definition
1. The solar spectrum that has been partially absorbed by gases between the Sun and the view on Earth.
2. A dark line in a continuous spectrum created when photons of a certain energy are absorbed by atoms or molecules. |
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Term
| What is a continuous spectrum (continuum)? |
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Definition
| A continuum is a spectrum of light over a range of wavelengths without any spectral lines. |
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Term
| What is the Doppler effect? |
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Definition
The Doppler effect (or Doppler shift) is the change in frequency of a wave for an observer moving relative to its source. The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession.
Blue shift = source moving towards you (high pitch siren)
Red shift = source moving away from you (low pitch siren) |
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Term
What is the mass and radius of the Sun? Use the Earth as a unit.
What is the Sun mostly composed of? |
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Definition
Mass = 3.33 x 10^5 Earth masses
Radius = 10^9 Earth radii
Composition (by mass) = 74% hydrogen, 25% helium, 1% other. |
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Term
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Definition
| The this shell of the Sun's gases we see are from its photosphere, the lowest level of its atmosphere. The gases in this layer shine nearly as a blackbody. The photosphere's base is at the top of the convection zone. |
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Term
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Definition
Convection is the transfer of energy by moving currents of fluid or gas containing that energy.
Convection of gas from below the photosphere produces features called granules. |
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Term
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Definition
| Above the photosphere and below corona is a layer of hotter, but less dense, gas called the chomosphere. Jets of gas, called spicules, rise up into the chomosphere along the boundaries of supergranules. |
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Term
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Definition
| The outermost layer of thin gases in the solar atmosphere, called the corona, extends outward to become the solar wind at great distances from the Sun. The gases of the corona are very hot, but they have extremely low densities. |
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Term
| How long are the cycles of the variations of the Sun's surface features? |
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Definition
| Some surface features on the Sun vary periodically in an 11-year cycle, and the magnetic fields that cause these changes actually vary over a 22-year cycle. |
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Term
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Definition
| Sunspots are relatively cool regions produced by local concentrations of the Sun's magnetic field protruding through the photosphere. The average number of sunspots and their average latitude vary in an 11-year cycle. |
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Term
| Describe nuclear fusion and Einstein's equation, E=mc^2. |
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Definition
Thu Sun's energy is produced by the thermonuclear process called hydrogen fusion, in which four hydrogen nuclei release energy when they fuse to produce a single helium nucleus.
The energy released in a thermonuclear reaction comes from the conversion of matter into energy, according to Einstein's equation. |
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Term
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Definition
Distances to the nearer starts (not the super far ones) can be determined by stellar parallax, which is the apparent shift of a star's location against the background stars while Earth moves along its orbit around the Sun.
distances to more remote starts are determined using spectroscopic parallax. |
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Term
| What is the apparent magnitude (of a star)? |
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Definition
| The apparent magnitude of a star, denoted m, is a measure of how bright the start appears to Earth-based observers. |
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Term
| What is the absolute magnitude (of a star)? |
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Definition
The absolute magnitude of a star, denoted M, is a measure of the star's true brightness and is directly related to a star's energy output, or luminosity.
The absolute magnitude of a star is the apparent magnitude it would have if viewed from a distance of 10 pc. Absolute magnitudes can be calculated from the star's apparent magnitude and distance from Earth. |
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Term
| Define the inverse-square law. |
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Definition
| The inverse-square law is the gravitational attraction between two objects and the apparent brightness of a light source are both inversely proportional to the square of its distance. |
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Term
| What is the Hertzprung-Russell (H-R) diagram? |
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Definition
The H-R diagram is a graph on which luminosities of starts are plotted against their spectral types (or, equivalently, their absolute magnitudes are plotted against surface temperatures.
The H-R diagram reveals the existence of four major groupings of stars: main-sequence starts, giants, super-giants, and white dwarfs. |
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Term
| What is hurdle in finding stellar masses? |
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Definition
| The hurdle for in finding stellar masses in that it can't be done directly by examining isolate stars. The mass of star can be determined only by its gravitational effects on other bodies, using Newton's law of gravity. |
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Term
| What do stellar masses tell us? |
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Definition
| Stellar masses are related to a stars luminosity and its location on the H-R diagram. The mass determines the amount of energy each star has available to manufacture light and other electromagnetic radiation. |
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