Astronomy Exam 2 Written Questions + Smartwork

What is an accretion disk, and what are its characteristics? Select the true statements regarding accretion disks.

- an accretion disk's radius is typically hundreds of AU - conservation of angular momentum leads a cloud to form a disk rather than collapse entirely - the shape and motion of the accretion disk are the reason that the subsequently formed planets all orbit in or near the equatorial plane of the star explanation: The cloud collapses towards its equatorial plane, but it does not collapse inward toward its axis of rotation due to conservation of angular momentum. (There is no force preventing the disk from flattening out.) A protostar forms in the center of the disk, and most of the remaining material is ejected back into interstellar space. What remains is the material from which planets, moons, comets, asteroids and other debris form. The accretion disk is typically much larger than the orbits of the planets it will eventually form. Large planets mostly form within tens of AU of the star, but the disk is much larger. If a cloud were perfectly round and had no rotation whatsoever, it would simply shrink into a smaller ball, rather than forming a disk. It is the angular momentum, which results from rotation, that leads to the eventual disk shape. Because they are born out of the disk, the planets will orbit the star in the plane of the disk, unless collisions skew their orbits, or the planets are ejected out of the star's planetary system.

Which of the following is a reason that all large astronomical telescopes are reflecting telescopes?

- reflecting telescopes minimize chromatic aberration - reflecting telescopes can be designed to be shorter than refracting telescopes - reflecting telescopes are not as heavy as refracting telescopes explanation: Refracting telescopes have several limitations that make them not suitable for large telescope designs. For example, chromatic aberration is a phenomenon associated with refracting telescopes: the refraction takes place within the glass lenses. The large, heavy primary lens placed at the top of a refracting telescope limits its size. By contrast, reflecting telescopes can be made larger because they are supported from the bottom and won't warp under their own weight. The mirrors within a reflecting telescope can "fold" the light, thus allowing for reductions in the length and thus the weight of the telescope.

Which of the following can astronomers determine directly from the spectrum of an object?

- speed toward or away from an observer - temperature - composition explanation: The spectrum of an object can tell us the temperature from the peak of its blackbody curve, the composition from the wavelengths of absorption or emission lines, and the speed toward or away from us from the Doppler shift of those lines.

Which of the following quantities contribute to the angular momentum of a spinning object on the surface of the Earth?

- the distribution of the mass of the object - the mass of the object - the rate of spin of the object

Choose all that apply. CCD cameras are better astronomical detectors than the human eye because

- the integration time can be longer - they can observe at wavelengths beyond the visible - their quantum efficiency is higher explanation: CCD cameras are more sensitive than the eye to light, detecting as much as 90% of the photons striking it compared to only about 10% for the eye. A camera can also be left open for a long time and record all the photons that strike it during that time, whereas the eye has a fixed exposure time of about a tenth of a second. Also the human eye sees only a tiny range of wavelengths compared to the vast possibilities of the entire EM spectrum that astronomers want to investigate.

Astronomers may describe certain objects as being redshifted or blueshifted. Select all true statements about this phenomenon from those listed below.

- these objects are exhibiting the doppler effect - wavelengths of light from the objects differ from expected (rest) wavelengths because the object is moving away from (redshifted) or toward (blueshifted) the observer explanation: Light from approaching objects is blueshifted, and light from receding objects is redshifted. This is called the Doppler effect. If an object is moving toward you, the light reaching you from the object has a shorter wavelength than the light emitted by the object. (Think of the visible spectrum, where blue has a shorter wavelength than red.) We say that the light from the object is blueshifted. Notice in the figure below that the waves are squeezed as the object moves toward the observer. Conversely, if an object is moving away from you, the light reaching you is redshifted, or stretched. Redshift and blueshift do not mean the light is primarily visible or that it is primarily red or blue. It means only that the light the object is emitting is more red or more blue than if the object were at rest.

Put the following stages of planet formation in order of occurrence. (Earliest stage --> Latest stage)

1. An interstellar cloud collapses into a disk of gas, dust 2. Gas pushes smaller dust grains into larger grains 3. Larger dust grains grow into clumps 4. Clumps of dust collide and stick, forming planetesimals 5. Km-sized planetesimals attract other objects by gravity 6. Planets of various sizes form explanation: The process of planet formation begins with a cloud of dust and gas that collapses to form an accretion disk. Within the disk, random motions of the gas push the dust around, and some of the dust sticks together to form larger and larger grains, eventually becoming clumps. With continued collisions, 100-meter clumps of dust grow into kilometer-sized planetesimals, which have enough gravity to grow still larger by pulling in and capturing other smaller planetesimals. The process continues until planets of various sizes are formed.

Rank the following events in the order that corresponds to the formation of a planetary system (earliest stage --> latest stage)

1. Gravity collapses a cloud of interstellar gas 2. A rotating disk forms and dust grains stick together by static electricity 3. Small bodies collide to form larger bodies 4. Primary atmospheres form 5. A stellar wind "turns on" and sweeps away gas and dust, removing primary atmospheres from planets 6. Secondary atmospheres form

Rank the types of radiation in order of their energy, from least to greatest. red visible light, x rays, blue visible light, infrared, radio waves, gamma rays

1. Radio waves 2. infrared 3. red visible light 4. blue visible light 5. x rays 6. gamma rays explanation: Light of greater energy has a shorter wavelength. Therefore, the order from least to greatest energy is the same as the order of longest to shortest wavelength: radio waves, infrared, red visible light, blue visible light, X-rays, and gamma rays.

Rank the following in order of decreasing wavelength. infrared, ultraviolent, gamma rays, visible, radio waves

1. Radio waves 2. infrared 3. visible 4. ultraviolet 5. gamma rays

The light-gathering power of a 4-meter telescope is __________ than that of a 2-meter telescope.

4 times larger explanation: The light-gathering power of a telescope depends on the area of the aperture, and since area scales as size2, two times bigger size is 22 = 4 times more light-gathering power.

A new star is forming inside this glowing cloud of gas. The dark band in the middle is made of a disk of thick dust, which obscures the light within it and hides the forming star from view. Newly forming stars are surrounded by gas and dust. Based on this observation, what is the most likely scenario for the formation of the Solar System?

A cloud of gas and dust collapsed into a flattened disk, within which the Sun and planets formed explanation: A collapsing cloud that flattens into a disk explains the disk shape of our Solar System, where the planets all orbit near the same flat plane. The planets orbit in the same direction as the cloud they formed from was rotating in. Most other options would not explain this flat shape and the orderly orbits, and star collisions are so rare that that formation scenario is highly unlikely.

Written question: What is the constraint on the energy of light that can absorbed and emitted by an atom?

A given atom may have many energy states available to it, but those states are discrete. When electrons in an atom gain or lose energy, the atom shifts from one energy state to another. Because the atom's energy states are discrete, the electrons must gain or lose energy in particular amounts, corresponding to the difference between energy levels in the atom. An electron cannot gain an amount of energy that puts the atom between states. Atoms absorb and emit radiation at unique wavelengths, giving them special fingerprints. Charlotte's answer: The constraint is that they can only occupy certain energy levels and the energy of the light has to match the change in the difference in the energy levels. (LOOK ON PAGES 134-137)

Written question: Why are large diameter telescopes better than small diameter telescopes? Provide at least 2 reasons.

A larger diameter telescope is better due to 1. the larger aperture. And 2. ____________. In making the diameter larger, the aperture is increased. Aperture is the area of the lens, and the lens is a device that uses refraction to bend light. When the aperture is bigger, the angle of light that can be let in is higher. This way people can get a clearer view of images they are trying to obtain in space.

Why is an iron atom a different element from a sodium atom?

A sodium atom has fewer neutrons in its nucleus than an iron atom Explanation: A given element is defined by the number of protons in its nucleus, not neutrons. A nucleus with a different number of neutrons is considered an isotope of a given element that has a similar number of protons. Because iron has more protons in its nucleus than sodium, it is a different element.

Which of the following can be fully observed from Earth's surface? A. visible light B. radio waves C. x-ray light D. gamma radiation E. UV light

A. visible light and B. radio waves explanation: Radiation with shorter wavelengths than visible light are all (or in the case of UV, mostly) blocked by our atmosphere.

Identify where each type of light belongs on the electromagnetic spectrum by dragging each to the target representing its wavelength. You may need to use the arrow icon to view all of the options. A. Visible Light B. X-Ray C. Microwave D. Gamma Ray E. Radio Wave F. UV Ray G. Infrared light

Answer (from left to right: longest wavelength to shortest wavelength) E. Radio wave (10^3) G. Infrared Light (10^-5) F. UV light (10^-8) D. Gamma Ray (10^-12) Explanation: Radio waves can penetrate the atmosphere and have the longest wavelengths, about the size of buildings. Only some infrared light can penetrate the atmosphere. Wavelengths of infrared light are slightly longer than visible light and are about the size of a pinpoint. Ultraviolet (UV) light cannot penetrate the atmosphere because of the ozone layer. UV light has wavelengths of just less than the wavelengths of visible light, about the size of molecules. Gamma rays have the shortest wavelengths of light. Gamma rays cannot penetrate the atmosphere and are the most damaging form of radiation.

Written question: What is 'atmospheric seeing' and how do we correct for it in telescope images?

Atmospheric seeing is the limit on the angular resolution of a telescope on the surface of Earth caused by atmospheric distortion. When light enters the atmosphere, bubbles of warm air distort the parallel wavelengths. By the time these waves reach the telescope lens on Earth, they are distorted. This degrades angular resolution and causes images to become blurred. To fix this problem, we use adaptive optics. This solution compensates for much of the atmosphere's distortion.

Written question: How do the wavelengths and energies of radio waves, infrared light, visible light, ultraviolet light, and x-rays compare?

Book page #'s 114 and 115 Radio waves: The longest wavelength out of these options and the least amount of energy. The light of these wavelengths in the form of FM, AM, television, and cell phone signals is used to transmit information. Infrared light: Longer wavelengths (and less energy) than the reddest wavelengths in the visible range. You often feel infrared light as heat. Infrared radiation is used in television remote controls. Night vision goggles detect infrared radiation from warm objects such as animals. Infrared wavelengths are longer than about 0.75 microns (the red end of the visible range) and shorter than 500 microns. Visible light: Lies between violet (about 380nm) and red (750nm). Stretched out between violet and red are the other colors of the rainbow Ultraviolet light: Has wavelengths between 40 and about 380 nm-- longer than X-rays but shorter than visible light. UV light has enough energy to penetrate your skin, but not much deeper (unlike x-rays). x-rays: longer wavelength than gamma rays (which has the shortest wavelength of all w/ the highest energy). However, shorter wavelength and higher energy + frequency than all of the options provided in this question. Because of its high energy and frequency, it penetrates matter easily. Has wavelengths between 0.1 and 40nm. **REMEMBER: - shorter wavelength = higher energy + frequency - longer wavelength = lower energy + frequency Order from shortest wavelength to longest wavelength 1. gamma rays 2. x-rays 3. ultraviolet 4. visible 5. infrared 6. microwave 7. radio Acronym: George's Xylophone Used Viagra In My Room

Arrays of radio telescopes can produce much better resolution than single-dish telescopes because they work based on the principle of A. refraction B. diffraction C. reflection D. interference

D. interference Explanation: Interference is the wave phenomenon in which two or more waves are combined to create an effective resultant wave. In a radio telescope array, the interference phenomenon occurs as the individual radio telescope signals are combined to create one effective radio signal. The combined signal has a resolution as high as if it came from a very large telescope with much better resolution.

How does the spectrum of a distant star reveal the star's chemical composition?

Dark lines, also called absorption lines, within the spectra are "fingerprints" for the different atoms and molecules within a star's atmosphere. explanation: Each atom and molecule absorbs specific wavelengths of light that correspond to unique differences in energy levels of their structures. This in turn produces a specific set of dark lines in the spectrum for each atom and molecule -- that is, a unique spectral "fingerprint" for each.

Written question: Why do we have two high tides a day? And why are the high tides separated in time by about 12 hours and 25 minutes, instead of every 12 hours?

Earth's rotation period of one day is much shorter than the Moon's orbital period of about a month. Over one day, the Moon only moves a little way in its orbit, but you travel around Earth once. Each day, the Moon rises 50 minutes later than it did on the previous day, so the time between the moon's return to the same position in the sky from the previous day is 24h 50m. There are two high tides and two low tides each day: "Begin as the rotating Earth carries you through the tidal bulge on the Moonward side of the planet. Because Earth's rotation drags the tidal bulge, the moon is not exactly overhead but is instead high in the western sky. When you are at the high point in the tidal bulge, high tide occurs. The rotation of Earth then carries you around to a point where ocean water is lower than average--called a low tide. Later, you pass through a region where the ocean water is "left behind" (with respect to Earth as a whole) in the tidal bulge on the side of Earth that is away from the Moon. At this high tide, the Moon at that time is hidden from view on the far side of Earth. After the Moon has risen above the eastern horizon, you pass through a second low tide. After 24 h 50 m--the amount of time the moon takes to return to the same point in the sky from which it started--you again pass through the tidal bulge on the near side of the planet. Each of these tides occurs about 6 1/4 hours after the previous one, because there are 4 tides, and 1/4 of 24h 50m is about 6 1/4 hours. That is the age-old pattern by which mariners have lived their lives for millennia: the twice-daily coming and going of high tide, shifting through the day in lockstep with the passing of the Moon" (p. 98 from the book).

Planets must form somehow within the flattened protoplanetary disk. A clue to this process comes from meteorites, which are pieces of debris that have fallen from space to Earth. Most are made of materials that have remained unchanged since the time that the Solar System was first forming, which make them excellent indicators of what conditions were like during that time. Study this picture of a meteorite that has been sliced open to show its interior, and use your observations to determine the most likely formation scenario for a planet. Scroll down and select the best answer below.

Individual particles in the nebula stick together to form larger pieces, which later collide with and stick to other pieces to gradually form larger objects, which eventually grow to the size of a planet explanation: The mottled appearance of meteorite interior suggests that planets were formed by smaller pieces that stuck together to form larger ones.

Written question: Why are all large telescopes reflectors?

Large telescopes are mainly reflectors for technical purposes. Refracting telescopes require a large lens and this is more expensive to make. On top of that, refracting telescopes tend to sag under their own weight. The reflecting telescope uses two mirrors to bring light to a focus. Instead of risking the issues and expenses that come with making large refracting telescopes, it is easier to produce large, high quality optic mirrors for a reflecting telescope.

The resolution of radio telescopes suffers greatly from the large wavelengths of the light they are observing. What can be done to a radio telescope to improve its angular resolution?

Make its dish bigger

Written question: Why do astronauts feel weightless when abroad the space station?

Smartwork: they are falling around Earth at the same rate as the shuttle Smartwork explanation: Astronauts in a space shuttle are still under the effect of Earth's gravity. Gravitational force counters the velocity of the shuttle and astronauts to keep them in orbit. Astronauts in orbit experience the same gravitational force and acceleration as the space shuttle and experience the same orbit. Astronauts feel weightless because the shuttle does not press against them in the same way as the ground "presses" on Earth.

Spring Tide versus Neap tide

Spring Tide: full moon, new moon (when the sun and the moon are aligned with the earth) Leap Tide: 1st quarter, 3rd quarter explanation: When the Sun, Earth, and Moon are lined up in a row, the Sun and Moon work together to make the tides on Earth stronger. This is referred to as a spring tide. When the Sun and Moon are at right angles with respect to the Earth, their gravitational pulls oppose each other and the tides on Earth are weaker. This is referred to as a neap tide.

You are shopping for telescopes online. You find two in your price range. One of these has an aperture of 20 cm, and one has an aperture of 30 cm. Which should you choose, and why?

The 30cm, because the light-gathering power will be better explanation: Light-gathering power is the most important property of a telescope. When more light is gathered the image has a higher resolution and can be magnified more if need be.

Written question: What is the Doppler effect and how can it provide information about astronomical objects?

The Doppler Effect can help us measure the motion of distant objects. Because of the Doppler effect, light from receding objects is redshifted to longer wavelengths, and light from approaching objects is blue-shifted to shorter wavelengths. The wavelength shifts of the spectral lines indicate how fast an astronomical object is moving toward or away from Earth. How the Doppler effect applies to sound waves: "If you are standing in front of the object, the waves that reach you have a shorter wavelength and therefore a higher frequency than the waves given off by the object when it is not moving. Conversely, if an object is moving away from you, the waves reaching you from the object are spread out (longer wavelength, lower frequency). That change in frequency is known as the Doppler effect" (from the book, p.128) How the Doppler effect applies to light waves: If a star is at rest relative to you, then it emits light with the rest wavelength. If a star is moving TOWARD you, the light reaching you from the star has a shorter wavelength than its rest wavelength. The light is "bluer" than the rest wavelength, and the light is blueshifted. In contrast, light from a star moving AWAY from you is shifted to longer, redder wavelengths. The light is redshifted. The amount by which the wavelength of light is shifted by the Doppler effect is called the light's Doppler shift, which depends on the speed of the object emitting the light; faster objects have larger shifts.

There is friction between the layers of the Earth, which causes the tidal bulge to be dragged along as the Earth rotates, pulling it out of alignment with the line connecting the Moon and Earth. The gravity of this off-center bulge has an effect on the Moon. Study the above figure, and choose the statement below that follows from it.

The moon used to be closer to earth than it is now Explanation: The moon used to be significantly closer to us than it is now, and in the future it will be farther away.

Space telescopes that exist in orbit above most of Earth's atmosphere are expensive, so they must therefore be supported with a very compelling motivation. If you were trying to justify funding for a space telescope in orbit around the Earth, which of the following would be the best argument to use?

The telescope could observe wavelengths of light that are not visible from the ground explanation: In order to observe some types of light (gamma ray, X-ray, and some wavelengths of ultraviolet and infrared), we must put telescopes above the Earth's atmosphere.

Written question: Why are there very few space-based optical (visible light) telescopes, as compared to x-ray and infrared telescopes?

There are few space-based optical telescopes because these types of light are able to pass through our atmosphere. Certain X-Ray waves, infrared light and gamma rays cannot pass through, and it is for this reason that we send more telescopes to space to analyze these forms of light. On earth we can receive visible light and radio waves, if we can do these things on earth, it is more effective to analyze the light we cannot see in space.

Written question: How does the light emitted from a HOT object change as it is made even MORE HOT?

Thermal radiation: The hotter the material is, the more its particles accelerate. They speed up, slow down, and change direction. Each particle will be accelerated differently, across an entire range of changes of speed and direction. A charged particle radiates anytime it accelerates. The energy of the radiation (and therefore the frequency and the wavelength) depends on how much the particle is accelerated, so the jostling of particles that results from their thermal motions causes them to emit an entire range of electromagnetic radiation. Any material dense enough for its particles to be jostled by their neighbors emits light simply because of its temperature (page 132). Luminosity is the total amount of light emitted each second (energy per second, measured in watts, W) from a source. The hotter the object, the more energetically the charged particles within it move, and the more energy they emit in the form of electromagnetic radiation. In other words, an object is more luminous when it is hotter. ** "As an object gets hotter, the thermal motions of its particles become more energetic, producing not only more, but also more energetic photons. As the average energy of the photons that it emits increases, the average wavelength of the emitted photons becomes shorter, and the light from the object gets bluer. Thus, hotter objects are bluer. If you heat a piece of metal, the metal will glow--first a dull red, then orange, and then yellow. the hotter the metal becomes, the more the highly energetic blue photons become mixed with the less energetic red photons, and the color of the light shifts from red towards blue. The light becomes more intense and bluer as the metal becomes hotter. Changing the temperature of an object causes both its luminosity and its color to change in its spectrum." (132)

Astronauts in a space shuttle can float while orbiting Earth. Why are these astronauts weightless?

They are falling around Earth at the same rate as the shuttle Explanation: Astronauts in a space shuttle are still under the effect of Earth's gravity. Gravitational force counters the velocity of the shuttle and astronauts to keep them in orbit. Astronauts in orbit experience the same gravitational force and acceleration as the space shuttle and experience the same orbit. Astronauts feel weightless because the shuttle does not press against them in the same way as the ground "presses" on Earth.

When an electron moves from a higher energy level to a lower energy level in an atom,

a photon is emitted explanation: A downward transition gives off energy, meaning a photon is emitted.

Larger lenses in telescopes offer better resolution. Resolution is defined as the closest angular distance two objects can be apart from one another before their light merges together and they look like just one object. Therefore, smaller resolutions are better (closer objects can be separated). The resolution of the human eye is 1 arcminute, or 1/60th of a degree. If the light of two street lamps in the distance is separated by 0.5 arcminute, what will you see with your eyes?

a single light, with the combined brightness of each street lamp explanation: They are so close together that their light would blur into one single light, as seen by your eye.

The angular resolution of a ground-based telescope is usually determined by

atmospheric seeing explanation: The atmosphere is generally what limits everything that a telescope can do.

When you look at the sky on a dark night and see stars of different colors, which are the hottest? a. yellow b. blue c. red d. orange e. red-orange

b. blue explanation: Wien's Law states that as a star's surface temperature increases, the peak wavelength for the light produced shifts to wavelengths with decreasing value. As blue light has the smallest value for the options provided, it would have the greatest temperature associated with it.

An object in a(n) __________ orbit in the Solar System will remain in its orbit forever. An object in a(n) __________ orbit will escape from the Solar System.

bound; unbound explanation: As the name implies, bound orbits are bound forever to the object being orbited (barring some outside change). Both circular and elliptical orbits are examples of bound orbits.Unbound orbits are not bound to the object being orbited, and the object will only pass by it one time before escaping. Parabolic and hyperbolic orbits are examples of unbound orbits.

If scientists are interested in studying the composition of the early Solar System, the best objects to study are

comets and asteroids explanation: Asteroids and comets are made almost exclusively of the pristine material out of which the Solar System formed.

If we wanted to increase the Hubble Space Telescope's altitude above Earth and keep it in a stable orbit, we also would need to

decrease its orbital speed explanation: Increasing the speed would give it a boost of energy that would take the telescope farther out than its original orbit. As it falls back down toward the Earth, it would take a new elliptical path that has a larger average radius than before.

As wavelength increases, the energy of a photon __________ and its frequency __________.

decreases ; decreases explanation: As the wavelength increases, the frequency of the light decreases since the product of frequency and wavelength is a constant number (the speed of light). Also, since the energy carried by a wave is proportional to the frequency, the energy decreases when frequency decreases.

Cameras that use adaptive optics provide higher spatial-resolution images primarily because

deformable mirrors are used to correct the blurring due to earth's atmosphere explanation: Turbulence in the atmosphere distorts light as it passes from space to the telescope; adaptive optics are designed to remove these effects.

Review the spectrum here. Remembering that Earth has an atmosphere, how much of each type of light can we view from the ground?

gamma rays/x-rays (shorter wavelength): we can't observe it at all wavelength: 550 (visible light): we can observe 100% of it very long wavelength (television, etc.): we can observe some of it explanation: From the ground, only visible light is 100% observable. Radio, infrared, and ultraviolet light get blocked somewhat by our atmosphere. A good amount of radio waves pass through, but not 100%. X-rays and gamma rays are entirely blocked by our atmosphere because they are the two shortest wavelengths of light and thus can only be observed from space

If the distance between Earth and the Sun were cut in half, the gravitational force between these two objects would

increase by a factor of 4 explanation: The force of gravity follows an inverse square law with distance (d), scaling as d^-2. This means that a factor of 2 decrease in distance results in an increase in force of a factor of 2^2 = 4.

The nebular hypothesis describes what happens when a cloud collapses into a star system. Where does the majority of the angular momentum of the original cloud go?

into the orbital angular momentum of planets explanation: Calculations show that orbital angular momentum of planets is much higher than the spin angular momentum of the central stars, especially for planets that are very massive and far from the star, such as Jupiter.

As a blackbody becomes hotter, it also becomes __________ and __________.

more luminous; bluer explanation: The Stefan-Boltzmann law states that luminosity depends directly on temperature, so a hotter temperature will be more luminous. Wien's law says that hotter objects emit shorter wavelengths and thus appear bluer, so blue is hotter than red.

The problem of atmospheric seeing motivated the development of adaptive optics. This technology can correct for the change in the path of light in real time, with mirrors that deform to redirect the light rays back into a straight path to the detector. This produces images with much higher resolution, as in the figure below. The original view of the object is on the left; the version improved with adaptive optics is on the right. Besides adding adaptive optics to a telescope, what else can be done to reduce the effects of seeing?

put the telescope at a higher altitude (the height above sea level) explanation: The higher in altitude the telescope is, the less atmosphere light from astronomical objects must pass through to reach the telescope. As such, seeing is not as bad at higher altitudes. Seeing is eliminated completely if the telescope is placed above the atmosphere (for instance, in orbit around the Earth).

If the Moon had twice the mass that it does, how would the strength of the lunar tides change?

the highs would be higher and the lows would be lower explanation: Tidal force depends on the mass of the object creating the tide. This will make high tides higher, removing more water from the low-tide areas.

Earth speeds along at 29.8 km/s in its orbit. Neptune's nearly circular orbit has a radius of 4.5 × 109 km, and Neptune takes 164.8 Earth years to make one trip around the Sun. Calculate how fast Neptune moves along in its orbit.Make a prediction: Neptune is much farther from the Sun than Earth. Do you expect Neptune to move faster or slower in its orbit?

slower Explanation: We would expect Neptune to have a slower orbital speed than Earth, because it is much farther from the Sun than Earth is. According to Kepler's laws of planetary motion, objects farther from the Sun have both a greater distance to travel to complete an orbit and a slower speed over which they cover that distance.

Which of the following is the biggest disadvantage of putting a telescope in space?

space telescopes are much more expensive than similar ground-based telescopes

The direction of revolution in the plane of the Solar System was determined by

the direction of rotation of the original cloud explanation: The answer is the direction of rotation of the orginal cloud. As a molecular cloud begins to collapse, any initial rotation will increase as the collapse continues. Conservation of angular momentum perpetuates a disk shape for the cloud, which will eventually become a central star and planar distribution of planets will rotate and revolve in the same manner as the initial rotation.

Which astronomical body dominates the tides on Earth?

the moon explanation: Tides on Earth are a result of tidal forces. Tidal force is highly dependent on distance since it is due to a difference in gravitational force across a body (mathematically expressed as 1/d3). Since the Moon is so much closer to Earth than the Sun or Jupiter, the Moon has a higher influence on the tides. It is true that the Sun influences the tides, but since it is approximately 400 times farther away than the Moon, the influence decreases dramatically. Jupiter, being much less massive than the Sun and much farther away, has a negligible effect on our tides. also note: The part of Earth closest to the Moon experiences the strongest gravitational force from it and therefore bulges toward the Moon. Like pulling on a spring, the opposite side of the Earth also bulges out, and so the positions marked at 0º and 180º in the diagram are both experiencing high tide. Positions at 90º from these points experience the opposite effect: low tide.

Compared to your mass on Earth, on the Moon your mass would be

the same; mass doesn't change

Spacecraft are the most effective way to study planets in our Solar System because

they can collect more information than is available just from images