Astronomy Chapter Summaries

A planet is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighborhood around its orbit.

Dwarf planets don't clear their neighborhood of other objects, which is one of the requirements to be considered a planet.

This is due to the finite speed of light. The light we see from distant objects has taken a long time to reach us, so we are seeing them as they were in the past.

<p>The ecliptic is the apparent path of the Sun across the celestial sphere over a year. It is essentially the plane of Earth's orbit around the Sun.</p> Signup and view all the answers

<p>Imaginary patterns of stars along the celestial sphere</p> Signup and view all the answers

<p>Azimuth is the direction along the horizon, measured in degrees from north, where a celestial object is located. It is used to locate a celestial object in the sky.</p> Signup and view all the answers

<p>They're caused by the changing position of the moon as it orbits Earth, relative to the Earth-Sun line. This results in the changing amount of the sunlit side of the moon that is visible from Earth.</p> Signup and view all the answers

<p>New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third Quarter, Waning Crescent</p> Signup and view all the answers

<p>It means the moon rotates on its axis at the same rate that it orbits the Earth. As a result, we always see the same side of the moon from Earth.</p> Signup and view all the answers

<p>A lunar eclipse occurs when the Earth passes directly between the Sun and the Moon, casting a shadow on the Moon. This causes the Moon to appear darkened, sometimes with a reddish hue.</p> Signup and view all the answers

<p>The approximate radius of the Earth is 6,371 kilometers (3,959 miles).</p> Signup and view all the answers

<p>The geocentric model places the Earth at the center of the universe with the Sun and other planets orbiting around it.</p> Signup and view all the answers

<p>Apparent retrograde motion is the illusion that some planets appear to move backward in the sky against the background of stars. The geocentric model struggled to explain this phenomenon.</p> Signup and view all the answers

<p>Stellar parallax is the apparent shift in the position of a star against the background of more distant stars as viewed from different points in Earth's orbit. The measurement of this shift can then be used to calculate the distance to a star.</p> Signup and view all the answers

<p>The heliocentric model provided a more accurate explanation for the observed motions of the planets, including retrograde motion, which the geocentric model could not explain. It also led to a more precise understanding of planetary orbits compared to the geocentric model.</p> Signup and view all the answers

<p>Tycho Brahe, a Danish astronomer, spent years making precise naked-eye observations of the positions of stars, planets, and the Moon. These detailed observations provided crucial data for Johannes Kepler to formulate his three laws of planetary motion.</p> Signup and view all the answers

<p>Kepler's first law states that the planets orbit the Sun in elliptical paths, not circular paths, with the Sun at one focus of the ellipse.</p> Signup and view all the answers

<p>Kepler's second law states that a planet sweeps out equal areas in equal amounts of time as it orbits the Sun. This means that a planet moves faster when it is closer to the Sun and slower when it is further away.</p> Signup and view all the answers

<p>Galileo Galilei was the first person to use a telescope to observe the night sky. His observations provided significant evidence for the heliocentric model, including discovering moons orbiting Jupiter, the phases of Venus, and the mountains and valleys on the Moon.</p> Signup and view all the answers

<p>The scientific method is a systematic process of inquiry that involves making observations, formulating hypotheses, conducting experiments, analyzing data, and drawing conclusions.</p> Signup and view all the answers

<p>A law is a concise statement that describes a fundamental relationship or pattern observed in the natural world. It is often expressed as an if-then statement and is typically backed by a large amount of experimental evidence.</p> Signup and view all the answers

<p>A theory is a well-substantiated explanation for a natural phenomenon. It is based on a large body of evidence and is generally accepted by the scientific community.</p> Signup and view all the answers

<p>Occam's razor is a principle that states that, when faced with multiple explanations for a phenomenon, the simplest explanation with the fewest assumptions is generally the best.</p> Signup and view all the answers

<p>True</p> Signup and view all the answers

<p>Pseudoscience often makes claims that are not supported by evidence, ignores evidence that contradicts its claims, relies on anecdotes or personal experiences, and uses vague or exaggerated language. It also frequently lacks peer review and attempts to discredit scientific consensus.</p> Signup and view all the answers

<p>Right Ascension (RA) is the celestial equivalent of longitude. It measures the angular distance of a celestial object eastwards along the celestial equator, measured in hours, minutes, and seconds.</p> Signup and view all the answers

<p>Declination (Dec) is the celestial equivalent of latitude. It measures the angular distance of a celestial object north or south of the celestial equator, measured in degrees, arcminutes, and arcseconds.</p> Signup and view all the answers

<p>The origin of the RA/Dec system is defined as the position of the Sun on the celestial sphere during the vernal equinox, which occurs around March 20th or 21st.</p> Signup and view all the answers

<p>Scalars are physical quantities that have only magnitude and no direction. Examples include mass, time, speed, and temperature.</p> Signup and view all the answers

<p>Acceleration is a change in velocity over time. It can involve speeding up, slowing down, or changing direction. It is a vector quantity, meaning it has both magnitude and direction.</p> Signup and view all the answers

<p>Newton's first law of motion, also known as the law of inertia, states that an object at rest will remain at rest, and an object in motion will stay in motion at a constant velocity unless acted on by a net external force. This means objects tend to resist changes in their state of motion.</p> Signup and view all the answers

<p>Newton's second law of motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. It is expressed as F = ma, where F is force, m is mass, and a is acceleration.</p> Signup and view all the answers

<p>The law of gravity states that every object in the universe attracts every other object with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This is expressed as F = Gm1m2/r2, where F is the gravitational force, G is the gravitational constant, m1 and m2 are the masses of the objects, and r is the distance between their centers.</p> Signup and view all the answers

<p>Angular momentum is a measure of an object's rotational inertia. It is a conserved quantity, meaning it cannot be created or destroyed; it can only be transferred from one object to another.</p> Signup and view all the answers

<p>Wavelength is the distance between two successive crests or troughs of a wave, while frequency is the number of waves passing a given point per second. Wave speed is the speed at which the wave propagates, and it is related to wavelength and frequency by the equation: Wave speed = wavelength x frequency.</p> Signup and view all the answers

<p>The electromagnetic spectrum encompasses all forms of electromagnetic radiation, arranged in order of increasing energy. This includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.</p> Signup and view all the answers

<p>Mass energy is the energy contained within an object due to its mass, while kinetic energy is the energy an object possesses due to its motion.</p> Signup and view all the answers

<p>Thermal energy refers to the internal energy associated with the random motion of atoms and molecules within a substance. It is the energy of heat.</p> Signup and view all the answers

<p>Gravitational potential energy is the energy stored in an object due to its position in a gravitational field. The higher an object is above the ground, the more gravitational potential energy it possesses.</p> Signup and view all the answers

<p>Radiant energy is the energy carried by electromagnetic radiation, such as light. It can be transformed into other forms of energy or transferred to other objects.</p> Signup and view all the answers

<p>Wien's law states that the wavelength at which a blackbody emits the most radiation is inversely proportional to its temperature. This implies that hotter objects emit more radiation at shorter wavelengths.</p> Signup and view all the answers

<p>Light can interact with matter in several ways, influencing its properties and behaviors. During emission, matter converts thermal energy into radiant energy, like the light emitted by a star. Absorption happens when matter absorbs radiant energy, raising its temperature. Light can also pass through matter during transmission, like when light travels through a gas cloud. In reflection, light bounces off matter, as seen with planets reflecting sunlight.</p> Signup and view all the answers

<p>A spectrum is a display of light separated by wavelength. It appears as a rainbow-like band. A spectrum can be created using a prism or a diffraction grating.</p> Signup and view all the answers

<p>There are three main types of spectra. Continuous spectra are generated by hot, dense objects, like stars, and show a continuous range of wavelengths. Emission spectra arise from hot, thin gases and show only specific, bright lines. Absorption spectra occur when light from a hot, dense object passes through a cooler gas, causing specific wavelengths to be absorbed.</p> Signup and view all the answers

<p>The Doppler effect is the change in frequency of a wave due to the relative motion of the source of the wave and the observer. If the source emits a wave and moves toward the observer, the frequency of the wave is shifted higher. If the source moves away, the frequency is shifted lower.</p> Signup and view all the answers

<p>Refraction is the bending of light as it passes from one medium into another medium with a different density. This is caused by the change in the speed of light as it transitions between the two media.</p> Signup and view all the answers

<p>A lens in a telescope uses refraction to gather light rays and focus them to a focal point. This creates a magnified image.</p> Signup and view all the answers

<p>Angular resolution is the ability of a telescope or other optical instrument to distinguish between two separate, closely spaced objects or details. It essentially represents the smallest angle between two objects that can be resolved as separate. Larger telescopes with bigger apertures generally have better angular resolution.</p> Signup and view all the answers

<p>Light gathering power is a telescope's ability to collect light from faint objects. This is directly related to the area of the telescope's primary mirror or lens. Larger telescopes collect more light and hence can detect fainter objects.</p> Signup and view all the answers

<p>Magnification is a telescope's ability to enlarge the image of a celestial object. It is determined by the ratio of the focal length of the objective lens or mirror to the focal length of the eyepiece. Higher magnification makes objects appear larger but does not necessarily improve the detail or sharpness of the image.</p> Signup and view all the answers

<p>Optimal conditions for astronomical observations involve a dark sky with minimal light pollution, a high altitude to minimize atmospheric blurring, calm weather with minimal wind to minimize atmospheric distortion, and a dry location to reduce cloud cover.</p> Signup and view all the answers

<p>Radio waves, visible light, and some near-infrared and near-ultraviolet radiation can penetrate Earth's atmosphere. However, most infrared and ultraviolet radiation, as well as X-rays and gamma rays, are absorbed or scattered by the atmosphere.</p> Signup and view all the answers

<p>The solar system includes one star (the Sun), 8 planets, many dwarf planets, numerous moons, millions of asteroids, and trillions of comets.</p> Signup and view all the answers

<p>The inner solar system consists of the rocky planets Mercury, Venus, Earth, and Mars, and the asteroid belt. These objects are relatively small and dense. The outer solar system includes the gas giants Jupiter, Saturn, Uranus, and Neptune, the Kuiper belt, and the Oort cloud. These objects are larger and less dense than the inner objects.</p> Signup and view all the answers

<p>The catastrophic encounter hypothesis suggests that the planets formed from material that was ripped from the Sun during a close encounter with another star. This material later coalesced into planets in orbit around the Sun.</p> Signup and view all the answers

<p>The collapsing nebular theory postulates that the solar system formed from a rotating cloud of gas and dust, known as a nebula. The cloud collapsed under its own gravity, with most of the material forming the Sun at the center. The remaining material flattened into a disk, and the planets were born as smaller chunks of matter within that disk coalesced.</p> Signup and view all the answers

<p>The frost line refers to the distance from the Sun where hydrogen-based compounds like water, methane, and ammonia can freeze into solids. This played a crucial role in the differentiation of the composition of planets in the solar system.</p> Signup and view all the answers

<p>Jupiter and Neptune's gravitational influence played a significant role in shaping the asteroid belt and the Kuiper belt. Orbital resonances with these giant planets created gravitational disturbances that prevented the formation of a planet and cleared out empty spaces within these regions. The asteroid belt and the Kuiper belt are remnants of this process.</p> Signup and view all the answers

<p>Planetesimals are small, rocky or icy bodies that formed in the early solar system. They are the building blocks of planets. They collided and accreted over time, eventually forming planets.</p> Signup and view all the answers

<p>The currently accepted theory for the formation of the Moon is the giant impact hypothesis. This hypothesis posits that Earth collided with a Mars-sized planetesimal early in its history. The debris from this collision then coalesced to form the Moon.</p> Signup and view all the answers

<p>The inner planets, in order of increasing distance from the Sun, are Mercury, Venus, Earth, and Mars.</p> Signup and view all the answers

<p>The inner planets and Earth's moon, in order of increasing size, are: Earth's moon, Mercury, Mars, Venus, and Earth.</p> Signup and view all the answers

<p>The interior structure of a planet typically consists of a metallic core, a rocky mantle, and a rocky crust. The core is generally the densest part, followed by the mantle, and the crust is the least dense layer.</p> Signup and view all the answers

<p>Venus and Earth both have mostly molten, convective mantles and liquid outer cores. This is due to their larger size and internal heat. Mercury, Mars, and the Moon, on the other hand, have cooled off more rapidly due to their smaller size and have mostly solid interiors.</p> Signup and view all the answers

<p>Earth's atmosphere is primarily composed of nitrogen and oxygen, while Venus's atmosphere is dominated by carbon dioxide. Mars's atmosphere is also primarily carbon dioxide but is much thinner than Venus's.</p> Signup and view all the answers

<p>Venus's atmosphere is thick due to a runaway greenhouse effect. The planet's proximity to the Sun, combined with its dense carbon dioxide atmosphere, traps heat. This effect causes the surface temperature to rise to extremely high temperatures.</p> Signup and view all the answers

<p>The Caloris Basin is a very large impact crater on Mercury. It is one of the largest impact craters in the solar system. The impact that formed the basin is believed to have caused significant seismic activity on Mercury, resulting in the formation of unusual terrain features on the opposite side of the planet known as 'weird terrain'.</p> Signup and view all the answers

<p>Mercury's temperature range is extreme due to its proximity to the Sun. The side of the planet facing the Sun experiences very high temperatures, while the side facing away from the Sun is much colder. This large temperature difference is also caused by Mercury's slow rotation and lack of a substantial atmosphere to regulate temperature.</p> Signup and view all the answers

<p>The 2:3 spin-orbital resonance means that Mercury rotates three times for every two orbits it completes around the Sun. This unusual resonance is a key piece of evidence for confirming Einstein's theory of relativity.</p> Signup and view all the answers

<p>The eccentricity of Mercury's orbit, combined with its proximity to the Sun, causes its orbital speed to vary considerably.</p> Signup and view all the answers